Research Interests:
Background As with many plant species, current genome editing strategies in soybean are initiated by stably transforming a gene that encodes an engineered nuclease into the genome. Expression of the transgene results in a double-stranded... more
Background As with many plant species, current genome editing strategies in soybean are initiated by stably transforming a gene that encodes an engineered nuclease into the genome. Expression of the transgene results in a double-stranded break and repair at the targeted locus, oftentimes resulting in mutation(s) at the intended site. As soybean is a self-pollinating species with 20 chromosome pairs, the transgene(s) in the T0 plant are generally expected to be unlinked to the targeted mutation(s), and the transgene(s)/mutation(s) should independently assort into the T1 generation, resulting in Mendellian combinations of transgene presence/absence and allelic states within the segregating family. This prediction, however, is not always consistent with observed results. Results In this study, we investigated inheritance patterns among three different CRISPR/Cas9 transgenes and their respective induced mutations in segregating soybean families. Next-generation resequencing of four T0 p...
Research Interests:
Plastids comprise a complex set of organelles in plants that can undergo distinctive patterns of differentiation and redifferentiation during their lifespan. Plastids localized to the epidermis and vascular parenchyma are distinctive in... more
Plastids comprise a complex set of organelles in plants that can undergo distinctive patterns of differentiation and redifferentiation during their lifespan. Plastids localized to the epidermis and vascular parenchyma are distinctive in size, structural features and functions. These plastids are termed ‘sensory’ plastids, and data show their proteome to be distinct from chloroplast, with specialized stress-associated features. The distinctive sensory plastid proteome derives from spatio-temporal regulation of nuclear genes encoding plastid-targeted proteins. Perturbation caused by depletion of the sensory plastid-specific protein MSH1conditioned local, programmed changes in gene networks controlling chromatin, stressrelated phytohormone and circadian clock behavior, and producing a global, systemic stress response in the plant. A similar systemic stress response resulted from over-expression of a second sensory plastid protein, PPD3. We posit that the sensory plastid participates in sensing of plant environmental stress, integrating this sensory function with epigenetic and gene expression circuitry to condition heritable stress memory.
Research Interests:
Plastids comprise a complex set of organelles in plants that can undergo distinctive patterns of differentiation and redifferentiation during their lifespan. Plastids localized to the epidermis and vascular parenchyma are distinctive in... more
Plastids comprise a complex set of organelles in plants that can undergo distinctive patterns of differentiation and redifferentiation during their lifespan. Plastids localized to the epidermis and vascular parenchyma are distinctive in size, structural features and functions. These plastids are termed 'sensory' plastids, and here we show their proteome to be distinct from chloroplasts, with specialized stress-associated features. The distinctive sensory plastid proteome in Arabidopsis thaliana derives from spatio-temporal regulation of nuclear genes encoding plastid-targeted pro-teins. Perturbation caused by depletion of the sensory plastid-specific protein MutS HOMOLOG 1 conditioned local, programmed changes in gene networks controlling chromatin, stress-related phytohormone and circadian clock behavior, and producing a global, systemic stress response in the plant. We posit that the sensory plastid participates in sensing environmental stress, integrat-ing this sensory fu...
Research Interests:
Mutagenesis is a useful tool in many crop species to induce heritable genetic variability for trait improvement and gene discovery. In this study, forward screening of a soybean fast neutron (FN) mutant population identified an individual... more
Mutagenesis is a useful tool in many crop species to induce heritable genetic variability for trait improvement and gene discovery. In this study, forward screening of a soybean fast neutron (FN) mutant population identified an individual that produced seed with nearly twice the amount of sucrose (8.1% on dry matter basis) and less than half the amount of oil (8.5% on dry matter basis) as compared to wild type. Bulked segregant analysis (BSA), comparative genomic hybridization, and genome resequencing were used to associate the seed composition phenotype with a reciprocal translocation between chromosomes 8 and 13. In a backcross population, the translocation perfectly cosegregated with the seed composition phenotype and exhibited non-Mendelian segregation patterns. We hypothesize that the translocation is responsible for the altered seed composition by disrupting a β-ketoacyl-[acyl carrier protein] synthase 1 (KASI) ortholog. KASI is a core fatty acid synthesis enzyme that is invol...
Research Interests:
As metabolic centers, plant organelles participate in maintenance, defense and signaling. MSH1 is a plant-specific protein involved in organellar genome stability in mitochondria and plastids. Plastid depletion of MSH1 causes heritable,... more
As metabolic centers, plant organelles participate in maintenance, defense and signaling. MSH1 is a plant-specific protein involved in organellar genome stability in mitochondria and plastids. Plastid depletion of MSH1 causes heritable, non-genetic changes in development and DNA methylation. We investigated the msh1 phenotype using hemi-complementation mutants and transgene-null segregants from RNAi suppression lines to sub-compartmentalize MSH1 effects. We show that MSH1 expression is spatially regulated, specifically localizing to plastids within the epidermis and vascular parenchyma. The protein binds DNA and localizes to plastid and mitochondrial nucleoids, yet fractionation and protein:protein interactions data indicate that MSH1 also associates with the thylakoid membrane. Plastid MSH1 depletion results in variegation, abiotic stress tolerance, variable growth rate, and delayed maturity. Depletion from mitochondria results in 7-10% of plants altered in leaf morphology, heat to...
Research Interests:
The present study was undertaken to assess the relationship of morpho-physiological characters among themselves as well as with yield and its components of 40 pigeonpea genotypes. The analysis of variance revealed significant difference... more
The present study was undertaken to assess the relationship of morpho-physiological characters among themselves as well as with yield and its components of 40 pigeonpea genotypes. The analysis of variance revealed significant difference among the genotypes for three morpho-physiological characters viz., Leaf Area Index (LAI), Net Assimilation Rate (NAR) and Crop Growth Rate (CGR) at different stages of crop growth, yield and its component characters. All the three morpho-physiological characters were significantly and positively related among themselves at all stages of crop growth except LAI with NAR at 90 days-final stage. Seed yield was observed to be positively and significantly correlated with NAR at 75–90 days stage. Path coefficient analysis revealed highest positive direct effect on seed yield via LAI at 45 days, via NAR at 45–60 days stage and via CGR at 30–45 days stage. Hence, higher productivity of a crop depends upon the persistence of high LAI for its greater part of its vegetative phase, its longer duration of maximum CGR and its rapid attainment of higher LAI and CGR.
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The present study was conducted to assess the variability, heritability and relationships of green manuring traits at 45 and 60 days after sowing (DAS) and genetic diversity in different genotypes of Sunnhemp. Phenotypic coefficient of... more
The present study was conducted to assess the variability, heritability and relationships of green manuring traits at 45 and 60 days after sowing (DAS) and genetic diversity in different genotypes of Sunnhemp. Phenotypic coefficient of variation was higher for plant height, green and dry biomass at 45 DAS than at 60 DAS and for root nodule characters at 60 DAS than at 45 DAS. Heritability estimates were higher for ail the characters at 60 days stage than at 45 days stage. Significant positive relationship was observed among the plant height, green and dry biomass at both the stages and among root nodule characters at 60 DAS. Path analysis showed high positive direct effect of green biomass towards dry biomass both at 45 and 60 DAS. Based on D2 values, 30 genotypes were grouped into 9 clusters. Cluster II was the biggest with 9 genotypes followed by cluster I with 7 genotypes. Maximum inter-cluster distance was observed between cluster VI, and VII. The genotype Crota-GKVK-2, Crota-GKVK-3 (cluster VI) and Crota-L-1 (cluster VII) were found promising and genetically diverse for hybridization to generate more variability and for the selection of desirable segregants.
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Pre-harvest sprouting (PHS) due to prolonged rainfall leads to germination of grains before harvest. The sprouting of the grains in the spike causes reduction in the grain yield and deteriorates grain milling and baking quality (Sharma et... more
Pre-harvest sprouting (PHS) due to prolonged rainfall leads to germination of grains before harvest. The sprouting of the grains in the spike causes reduction in the grain yield and deteriorates grain milling and baking quality (Sharma et al., 1994). The development of the PHS tolerant wheat cultivars has been difficult through conventional breeding since PHS tolerance is a quantitative trait influenced by many environmental factors and controlled by several dormancy related genes (Bailey et al., 1999). PHS also involves genes expressed in the maternal plant as well as tissues belonging to the next generation: the embryo and the endosperm. The selection for PHS is done at maturity and desirable plants cannot be used for crossing in the same season. Development of molecular markers linked to genes/QTLs conferring PHS tolerance is an attractive alternative since the presence of the gene can be detected without waiting for phenotypic expression of the gene. Amber grained wheats have be...
Research Interests:
Research Interests:
Early canopy coverage is a desirable trait that promotes faster ground coverage, resulting in reduced soil evaporation, increased light interception, biomass production and weed suppression, all of which are important determinants of... more
Early canopy coverage is a desirable trait that promotes faster ground coverage, resulting in reduced soil evaporation, increased light interception, biomass production and weed suppression, all of which are important determinants of yield in soybean (Glycine max). Variation in traits comprising shoot architecture can influence canopy coverage, canopy light interception, canopy-level photosynthesis, and source-sink partitioning efficiency. However, little is known about the extent of phenotypic diversity of shoot architecture traits and their genetic control in soybean. Thus, we sought to understand the contribution of shoot architecture traits to canopy coverage and to determine the genetic control of these traits. We examined the natural variation for shoot architecture traits in a set of 399 diverse maturity group I soybean (SoyMGI) accessions to identify relationships between traits, and to identify loci that are associated with canopy coverage and shoot architecture traits. Can...
Research Interests:
Research Interests:
Background As with many plant species, current genome editing strategies in soybean are initiated by stably transforming a gene that encodes an engineered nuclease into the genome. Expression of the transgene results in a double-stranded... more
Background As with many plant species, current genome editing strategies in soybean are initiated by stably transforming a gene that encodes an engineered nuclease into the genome. Expression of the transgene results in a double-stranded break and repair at the targeted locus, oftentimes resulting in mutation(s) at the intended site. As soybean is a self-pollinating species with 20 chromosome pairs, the transgene(s) in the T0 plant are generally expected to be unlinked to the targeted mutation(s), and the transgene(s)/mutation(s) should independently assort into the T1 generation, resulting in Mendellian combinations of transgene presence/absence and allelic states within the segregating family. This prediction, however, is not always consistent with observed results. Results In this study, we investigated inheritance patterns among three different CRISPR/Cas9 transgenes and their respective induced mutations in segregating soybean families. Next-generation resequencing of four T0 p...
Research Interests:
Plastids comprise a complex set of organelles in plants that can undergo distinctive patterns of differentiation and redifferentiation during their lifespan. Plastids localized to the epidermis and vascular parenchyma are distinctive in... more
Plastids comprise a complex set of organelles in plants that can undergo distinctive patterns of differentiation and redifferentiation during their lifespan. Plastids localized to the epidermis and vascular parenchyma are distinctive in size, structural features and functions. These plastids are termed ‘sensory’ plastids, and data show their proteome to be distinct from chloroplast, with specialized stress-associated features. The distinctive sensory plastid proteome derives from spatio-temporal regulation of nuclear genes encoding plastid-targeted proteins. Perturbation caused by depletion of the sensory plastid-specific protein MSH1conditioned local, programmed changes in gene networks controlling chromatin, stressrelated phytohormone and circadian clock behavior, and producing a global, systemic stress response in the plant. A similar systemic stress response resulted from over-expression of a second sensory plastid protein, PPD3. We posit that the sensory plastid participates in sensing of plant environmental stress, integrating this sensory function with epigenetic and gene expression circuitry to condition heritable stress memory.
Research Interests:
Plastids comprise a complex set of organelles in plants that can undergo distinctive patterns of differentiation and redifferentiation during their lifespan. Plastids localized to the epidermis and vascular parenchyma are distinctive in... more
Plastids comprise a complex set of organelles in plants that can undergo distinctive patterns of differentiation and redifferentiation during their lifespan. Plastids localized to the epidermis and vascular parenchyma are distinctive in size, structural features and functions. These plastids are termed 'sensory' plastids, and here we show their proteome to be distinct from chloroplasts, with specialized stress-associated features. The distinctive sensory plastid proteome in Arabidopsis thaliana derives from spatio-temporal regulation of nuclear genes encoding plastid-targeted pro-teins. Perturbation caused by depletion of the sensory plastid-specific protein MutS HOMOLOG 1 conditioned local, programmed changes in gene networks controlling chromatin, stress-related phytohormone and circadian clock behavior, and producing a global, systemic stress response in the plant. We posit that the sensory plastid participates in sensing environmental stress, integrat-ing this sensory fu...
Research Interests:
Mutagenesis is a useful tool in many crop species to induce heritable genetic variability for trait improvement and gene discovery. In this study, forward screening of a soybean fast neutron (FN) mutant population identified an individual... more
Mutagenesis is a useful tool in many crop species to induce heritable genetic variability for trait improvement and gene discovery. In this study, forward screening of a soybean fast neutron (FN) mutant population identified an individual that produced seed with nearly twice the amount of sucrose (8.1% on dry matter basis) and less than half the amount of oil (8.5% on dry matter basis) as compared to wild type. Bulked segregant analysis (BSA), comparative genomic hybridization, and genome resequencing were used to associate the seed composition phenotype with a reciprocal translocation between chromosomes 8 and 13. In a backcross population, the translocation perfectly cosegregated with the seed composition phenotype and exhibited non-Mendelian segregation patterns. We hypothesize that the translocation is responsible for the altered seed composition by disrupting a β-ketoacyl-[acyl carrier protein] synthase 1 (KASI) ortholog. KASI is a core fatty acid synthesis enzyme that is invol...
Research Interests:
As metabolic centers, plant organelles participate in maintenance, defense and signaling. MSH1 is a plant-specific protein involved in organellar genome stability in mitochondria and plastids. Plastid depletion of MSH1 causes heritable,... more
As metabolic centers, plant organelles participate in maintenance, defense and signaling. MSH1 is a plant-specific protein involved in organellar genome stability in mitochondria and plastids. Plastid depletion of MSH1 causes heritable, non-genetic changes in development and DNA methylation. We investigated the msh1 phenotype using hemi-complementation mutants and transgene-null segregants from RNAi suppression lines to sub-compartmentalize MSH1 effects. We show that MSH1 expression is spatially regulated, specifically localizing to plastids within the epidermis and vascular parenchyma. The protein binds DNA and localizes to plastid and mitochondrial nucleoids, yet fractionation and protein:protein interactions data indicate that MSH1 also associates with the thylakoid membrane. Plastid MSH1 depletion results in variegation, abiotic stress tolerance, variable growth rate, and delayed maturity. Depletion from mitochondria results in 7-10% of plants altered in leaf morphology, heat to...
Research Interests:
The present invention provides methods for obtaining plants that exhibit useful traits by perturbation of plastid function in plant rootstocks and grafting the rootstocks to scions. Methods for identifying genetic loci that provide for... more
The present invention provides methods for obtaining plants that exhibit useful traits by perturbation of plastid function in plant rootstocks and grafting the rootstocks to scions. Methods for identifying genetic loci that provide for useful traits in plants and plants produced with those loci are also provided. In addition, plants that exhibit the useful traits, parts of the plants including seeds, and products of the plants are provided as well as methods of using the plants. Recombinant DNA vectors and transgenic plants comprising those vectors that provide for plastid perturbation are also provided
Research Interests:
Research Interests:
Mitochondrial-plastid interdependence within the plant cell is presumed to be essential, but measurable demonstration of this intimate interaction is difficult. At the level of cellular metabolism, several biosynthetic pathways involve... more
Mitochondrial-plastid interdependence within the plant cell is presumed to be essential, but measurable demonstration of this intimate interaction is difficult. At the level of cellular metabolism, several biosynthetic pathways involve both mitochondrial- and plastid-localized steps. However, at an environmental response level, it is not clear how the two organelles intersect in programmed cellular responses. Here, we provide evidence, using genetic perturbation of the MutS Homolog1 (MSH1) nuclear gene in five plant species, that MSH1 functions within the mitochondrion and plastid to influence organellar genome behavior and plant growth patterns. The mitochondrial form of the protein participates in DNA recombination surveillance, with disruption of the gene resulting in enhanced mitochondrial genome recombination at numerous repeated sequences. The plastid-localized form of the protein interacts with the plastid genome and influences genome stability and plastid development, with i...
Research Interests: Genetics, Plant Biology, Biology, Life Sciences, Oxidative Stress, and 15 moreMitochondria, Plant breeding and genetics, Medicine, Gene expression, Plant growth, Light, Mitochondrial Genome, Angiosperms, Genomic instability, Genetic Recombination, Plant cell, Adaptive Response, Biochemistry and cell biology, Chloroplasts, and high light
Multicellular eukaryotes demonstrate nongenetic, heritable phenotypic versatility in their adaptation to environmental changes. This inclusive inheritance is composed of interacting epigenetic, maternal, and environmental factors.... more
Multicellular eukaryotes demonstrate nongenetic, heritable phenotypic versatility in their adaptation to environmental changes. This inclusive inheritance is composed of interacting epigenetic, maternal, and environmental factors. Yet-unidentified maternal effects can have a pronounced influence on plant phenotypic adaptation to changing environmental conditions. To explore the control of phenotypy in higher plants, we examined the effect of a single plant nuclear gene on the expression and transmission of phenotypic variability in Arabidopsis (Arabidopsis thaliana). MutS HOMOLOG1 (MSH1) is a plant-specific nuclear gene product that functions in both mitochondria and plastids to maintain genome stability. RNA interference suppression of the gene elicits strikingly similar programmed changes in plant growth pattern in six different plant species, changes subsequently heritable independent of the RNA interference transgene. The altered phenotypes reflect multiple pathways that are kno...
Research Interests: Biology, Mitochondria, Biological Sciences, RNA interference, Plant Physiology, and 14 moreSorghum, DNA methylation, Flowers, Arabidopsis, Phenotype, Cell nucleus, Physiological Stress Markers, Base Sequence, Gibberellins, Inheritance Patterns, Gene expression profiling, Chloroplasts, Molecular Sequence Data, and Stress Physiological
The present study was conducted to assess the variability, heritability and relationships of green manuring traits at 45 and 60 days after sowing (DAS) in Sesbania genotypes. Phenotypic and genotypic coefficients of variation were higher... more
The present study was conducted to assess the variability, heritability and relationships of green manuring traits at 45 and 60 days after sowing (DAS) in Sesbania genotypes. Phenotypic and genotypic coefficients of variation were higher at 45 DAS as ...
Research Interests:
Apoptosis and inhibition of host gene expression are often associated with virus infections. Many viral polypeptides modulate apoptosis by direct interaction with highly conserved apoptotic pathways. Some viruses induce apoptosis during... more
Apoptosis and inhibition of host gene expression are often associated with virus infections. Many viral polypeptides modulate apoptosis by direct interaction with highly conserved apoptotic pathways. Some viruses induce apoptosis during late stages of the infection cycle, while others inhibit apoptosis to facilitate replication or maintain persistent infection. In previous work, we showed that Chilo iridescent virus (CIV) or CIV virion protein extract induces apoptosis in spruce budworm and cotton boll weevil cell cultures. Here, we characterize the product of a CIV gene ( iridovirus serine/threonine kinase; istk ) with signature sequences for S/T kinase and ATP binding. ISTK appears to belong to the superfamily, vaccinia-related kinases (VRKs). The istk gene was expressed in Pichia pastoris vectors. Purified ISTK (48 kDa) exhibited S/T kinase activity. Treatment with ISTK induced apoptosis in budworm cells. A 35-kDa cleavage product of ISTK retaining key signature sequences was ide...
Research Interests: Biology, Virology, Apoptosis, Medicine, Gene expression, and 13 moreLepidoptera, Biological Sciences, Protein Kinases, Animals, Molecular weight, Amino Acid Sequence, Recombinant Proteins, Adenosine Triphosphate, Virus-Cell interactions, Iridovirus, Molecular Sequence Data, binding sites, and Medical and Health Sciences
Research Interests:
Research Interests:
MSH1 is a plant-specific protein. RNAi suppression of MSH1 results in phenotype variability for developmental and stress response pathways. Segregation of the RNAi transgene produces non-genetic msh1 ‘memory’ with multi-generational... more
MSH1 is a plant-specific protein. RNAi suppression of MSH1 results in phenotype variability for developmental and stress response pathways. Segregation of the RNAi transgene produces non-genetic msh1 ‘memory’ with multi-generational inheritance. First-generation memory versus non-memory comparison, and six-generation inheritance studies, identifies gene-associated, heritable methylation repatterning. Genome-wide methylome analysis integrated with RNAseq and network-based enrichment studies identifies altered circadian clock networks, and phytohormone and stress response pathways that intersect with circadian control. A total of 373 differentially methylated loci comprising these networks are sufficient to discriminate memory from nonmemory full sibs. Methylation inhibitor 5-azacytidine diminishes the differences between memory and wild type for growth, gene expression and methylation patterning. The msh1 reprogramming is dependent on functional HISTONE DEACETYLASE 6 and methyltransf...
Research Interests:
Research Interests:
Apoptosis and inhibition of host gene expression are often associated with virus infections. Many viral polypeptides modulate apoptosis by direct interaction with highly conserved apoptotic pathways. Some viruses induce apoptosis during... more
Apoptosis and inhibition of host gene expression are often associated with virus infections. Many viral
polypeptides modulate apoptosis by direct interaction with highly conserved apoptotic pathways. Some viruses
induce apoptosis during late stages of the infection cycle, while others inhibit apoptosis to facilitate replication
or maintain persistent infection. In previous work, we showed that Chilo iridescent virus (CIV) or CIV virion
protein extract induces apoptosis in spruce budworm and cotton boll weevil cell cultures. Here, we characterize
the product of a CIV gene (iridovirus serine/threonine kinase; istk) with signature sequences for S/T kinase and
ATP binding. ISTK appears to belong to the superfamily, vaccinia-related kinases (VRKs). The istk gene was
expressed in Pichia pastoris vectors. Purified ISTK (48 kDa) exhibited S/T kinase activity. Treatment with ISTK
induced apoptosis in budworm cells. A 35-kDa cleavage product of ISTK retaining key signature sequences was
identified during purification. Pichia-expressed 35-kDa polypeptide, designated iridoptin, induced apoptosis
and inhibition of host protein synthesis in budworm and boll weevil cells. A mutation in the ATP-binding site
eliminated both kinase and apoptosis activity of iridoptin, suggesting that kinase activity is essential for
induction of apoptosis. Analysis with custom antibody confirmed that ISTK is a structural component of CIV
particles. This is the first demonstration of a viral kinase inducing apoptosis in any virus-host system and the
first identification of a factor inducing apoptosis or host protein shutoff for the family Iridoviridae.
polypeptides modulate apoptosis by direct interaction with highly conserved apoptotic pathways. Some viruses
induce apoptosis during late stages of the infection cycle, while others inhibit apoptosis to facilitate replication
or maintain persistent infection. In previous work, we showed that Chilo iridescent virus (CIV) or CIV virion
protein extract induces apoptosis in spruce budworm and cotton boll weevil cell cultures. Here, we characterize
the product of a CIV gene (iridovirus serine/threonine kinase; istk) with signature sequences for S/T kinase and
ATP binding. ISTK appears to belong to the superfamily, vaccinia-related kinases (VRKs). The istk gene was
expressed in Pichia pastoris vectors. Purified ISTK (48 kDa) exhibited S/T kinase activity. Treatment with ISTK
induced apoptosis in budworm cells. A 35-kDa cleavage product of ISTK retaining key signature sequences was
identified during purification. Pichia-expressed 35-kDa polypeptide, designated iridoptin, induced apoptosis
and inhibition of host protein synthesis in budworm and boll weevil cells. A mutation in the ATP-binding site
eliminated both kinase and apoptosis activity of iridoptin, suggesting that kinase activity is essential for
induction of apoptosis. Analysis with custom antibody confirmed that ISTK is a structural component of CIV
particles. This is the first demonstration of a viral kinase inducing apoptosis in any virus-host system and the
first identification of a factor inducing apoptosis or host protein shutoff for the family Iridoviridae.
Mitochondrial-plastid interdependence within the plant cell is presumed to be essential, but measurable demonstration of this intimate interaction is difficult. At the level of cellular metabolism, several biosynthetic pathways involve... more
Mitochondrial-plastid interdependence within the plant cell is presumed to be essential, but measurable demonstration of this intimate interaction is difficult. At the level of cellular metabolism, several biosynthetic pathways involve both mitochondrial-and plastid-localized steps. However, at an environmental response level, it is not clear how the two organelles intersect in programmed cellular responses. Here, we provide evidence, using genetic perturbation of the MutS Homolog1 (MSH1) nuclear gene in five plant species, that MSH1 functions within the mitochondrion and plastid to influence organellar genome behavior and plant growth patterns. The mitochondrial form of the protein participates in DNA recombination surveillance, with disruption of the gene resulting in enhanced mitochondrial genome recombination at numerous repeated sequences. The plastid-localized form of the protein interacts with the plastid genome and influences genome stability and plastid development, with its disruption leading to variegation of the plant. These developmental changes include altered patterns of nuclear gene expression. Consistency of plastid and mitochondrial response across both monocot and dicot species indicate that the dual-functioning nature of MSH1 is well conserved. Variegated tissues show changes in redox status together with enhanced plant survival and reproduction under photooxidative light conditions, evidence that the plastid changes triggered in this study comprise an adaptive response to naturally occurring light stress.
Multicellular eukaryotes demonstrate nongenetic, heritable phenotypic versatility in their adaptation to environmental changes. This inclusive inheritance is composed of interacting epigenetic, maternal, and environmental factors.... more
Multicellular eukaryotes demonstrate nongenetic, heritable phenotypic versatility in their adaptation to environmental changes. This inclusive inheritance is composed of interacting epigenetic, maternal, and environmental factors. Yet-unidentified maternal effects can have a pronounced influence on plant phenotypic adaptation to changing environmental conditions. To explore the control of phenotypy in higher plants, we examined the effect of a single plant nuclear gene on the expression and transmission of phenotypic variability in Arabidopsis (Arabidopsis thaliana). MutS HOMOLOG1 (MSH1) is a plant-specific nuclear gene product that functions in both mitochondria and plastids to maintain genome stability. RNA interference suppression of the gene elicits strikingly similar programmed changes in plant growth pattern in six different plant species, changes subsequently heritable independent of the RNA interference transgene. The altered phenotypes reflect multiple pathways that are known to participate in adaptation, including altered phytohormone effects for dwarfed growth and reduced internode elongation, enhanced branching, reduced stomatal density, altered leaf morphology, delayed flowering, and extended juvenility, with conversion to perennial growth pattern in short days. Some of these effects are partially reversed with the application of gibberellic acid. Genetic hemicomplementation experiments show that this phenotypic plasticity derives from changes in chloroplast state. Our results suggest that suppression of MSH1, which occurs under several forms of abiotic stress, triggers a plastidial response process that involves nongenetic inheritance.
As metabolic centers, plant organelles participate in maintenance, defense, and signaling. MSH1 is a plant-specific protein involved in organellar genome stability in mitochondria and plastids. Plastid depletion of MSH1 causes heritable,... more
As metabolic centers, plant organelles participate in maintenance, defense, and signaling. MSH1 is a plant-specific protein involved in organellar genome stability in mitochondria and plastids. Plastid depletion of MSH1 causes heritable, non-genetic changes in development and DNA methylation. We investigated the msh1 phenotype using hemi-complementation mutants and transgene-null segregants from RNAi suppression lines to sub-compartmentalize MSH1 effects. We show that MSH1 expression is spatially regulated, specifically localizing to plastids within the epidermis and vascular parenchyma. The protein binds DNA and localizes to plastid and mitochondrial nucleoids, but fractionation and protein–protein interactions data indicate that MSH1 also associates with the thylakoid membrane. Plastid MSH1 depletion results in variegation, abiotic stress tolerance, variable growth rate, and delayed maturity. Depletion from mitochon-dria results in 7%–10% of plants altered in leaf morphology, heat tolerance, and mitochondrial genome stability. MSH1 does not localize within the nucleus directly, but plastid depletion produces non-genetic changes in flowering time, maturation, and growth rate that are heritable independent of MSH1. MSH1 depletion alters non-photoactive redox behavior in plastids and a subset of mitochondrially altered lines. Ectopic expression produces deleterious effects, underlining its strict expression control. Unraveling the complexity of the MSH1 effect offers insight into triggers of plant-specific, transgenerational adaptation behaviors.
Plant phenotypes respond to environmental change, an adaptive capacity that is at least partly transgenerational. However, epigenetic components of this interplay are difficult to measure. Depletion of the nuclear-encoded protein MSH1... more
Plant phenotypes respond to environmental change, an adaptive capacity that is at least partly transgenerational. However, epigenetic components of this interplay are difficult to measure. Depletion of the nuclear-encoded protein MSH1 causes dramatic and heritable changes in plant development, and here we show that crossing these altered plants with isogenic wild type produces epi-lines with heritable, enhanced growth vigour. Pericentromeric DNA hypermethylation occurs in a subset of msh1 mutants, indicative of heightened trans-poson repression, while enhanced growth epi-lines show large chromosomal segments of differential CG methylation, reflecting genome-wide reprogramming. When seedlings are treated with 5-azacytidine, root growth of epi-lines is restored to wild-type levels, implicating hypermethylation in enhanced growth. Grafts of wild-type floral stems to mutant rosettes produce progeny with enhanced growth and altered CG methylation strikingly similar to epi-lines, indicating a mobile signal when MSH1 is downregulated, and confirming the programmed nature of methylome and phenotype changes.