Search Results (86)

Sporisorium scitamineum is a biotrophic fungus responsible for inducing sugarcane smut disease that results in significant reductions in sugarcane yield. Resistance mechanisms against sugarcane smut can be categorized into structural, biochemical, and physiological resistance. However, structural resistance has been relatively understudied. This study found that sugarcane variety ZZ9 displayed structural resistance compared to variety GT42 when subjected to different inoculation methods for assessing resistance to smut disease. Furthermore, the stomatal aperture and density of smut-susceptible varieties (ROC22 and GT42) were significantly higher than those of smut-resistant varieties (ZZ1, ZZ6, and ZZ9). Notably, S. scitamineum was found to be capable of entering sugarcane through the stomata on buds. According to the RNA sequencing of the buds of GT42 and ZZ9, seven Expansin protein-encoding genes were identified, of which six were significantly upregulated in GT42. The two genes c111037.graph_c0 and c113583.graph_c0, belonging to the α-Expansin and β-Expansin families, respectively, were functionally characterized, revealing their role in increasing the stomatal aperture. Therefore, these two sugarcane Expansin protein-coding genes contribute to the stomatal aperture, implying their potential roles in structural resistance to sugarcane smut. Our findings deepen the understanding of the role of the stomata in structural resistance to sugarcane smut and highlight their potential in sugarcane breeding for disease resistance. Full article

Expansins are cell wall (CW) proteins that mediate the CW loosening and regulate salt tolerance in a positive or negative way. However, the role of Populus trichocarpa expansin A6 (PtEXPA6) in salt tolerance and the relevance to cell wall loosening is still unclear in poplars. PtEXPA6 gene was transferred into the hybrid species, Populus alba × P. tremula var. glandulosa (84K) and Populus tremula × P. alba INRA ‘717-1B4’ (717-1B4). Under salt stress, the stem growth, gas exchange, chlorophyll fluorescence, activity and transcription of antioxidant enzymes, Na⁺ content, and Na⁺ flux of root xylem and petiole vascular bundle were investigated in wild-type and transgenic poplars. The correlation analysis and principal component analysis (PCA) were used to analyze the correlations among the characteristics and principal components. Our results show that the transcription of PtEXPA6 was downregulated upon a prolonged duration of salt stress (48 h) after a transient increase induced by NaCl (100 mM). The PtEXPA6-transgenic poplars of 84K and 717-1B4 showed a greater reduction (42–65%) in stem height and diameter growth after 15 days of NaCl treatment compared with wild-type (WT) poplars (11–41%). The Na⁺ accumulation in roots, stems, and leaves was 14–83% higher in the transgenic lines than in the WT. The Na⁺ buildup in the transgenic poplars affects photosynthesis; the activity of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT); and the transcription of PODa2, SOD [Cu-Zn], and CAT1. Transient flux kinetics showed that the Na⁺ efflux of root xylem and leaf petiole vascular bundle were 1.9–3.5-fold greater in the PtEXPA6-transgenic poplars than in the WT poplars. PtEXPA6 overexpression increased root contractility and extensibility by 33% and 32%, indicating that PtEXPA6 increased the CW loosening in the transgenic poplars of 84K and 717-1B4. Noteworthily, the PtEXPA6-promoted CW loosening was shown to facilitate Na⁺ efflux of root xylem and petiole vascular bundle in the transgenic poplars. We conclude that the overexpression of PtEXPA6 leads to CW loosening that facilitates the radial translocation of Na⁺ into the root xylem and the subsequent Na⁺ translocation from roots to leaves, resulting in an excessive Na⁺ accumulation and consequently, reducing salt tolerance in transgenic poplars. Therefore, the downregulation of PtEXPA6 in NaCl-treated Populus trichocarpa favors the maintenance of ionic and reactive oxygen species (ROS) homeostasis under long-term salt stress. Full article

The expansin genes are commonly expressed in plant cells, and the encoded proteins influence plant growth and stress resistance by loosening the structure and increasing the flexibility of the cell wall. The objective of this study was to characterize expansin gene promoters in Populus trichocarpa to clarify the regulatory mechanisms underlying gene expression and evolution. Sequence alignments revealed that the similarity among 36 poplar expansin genes was greater for the coding sequences than for the promoter sequences, which suggested these promoter sequences evolved asynchronously. The bases flanking the start codon exhibited a usage bias, with sites +3, +4, and +5 biased toward GC, whereas the other sites were biased toward AT. The flanking sites were significantly correlated with gene expression, especially sites −10 and −17, in which C and G are the bases positively associated with gene expression. A total of 435 regulatory elements (61 types) were identified on the promoters of the poplar expansin genes; Skn-1 was the most common element in 23 promoters. Some expansin genes had more regulatory elements on their promoters (e.g., PtrEXPA4, PtrEXPA3, PtrEXPB3, and PtrEXPB1), whereas some others had less (e.g., PtrEXLA2, PtrEXLB1, and PtrEXPA23). Furthermore, 26 types of elements were involved in expansin gene expression, 25 of which positively affected expression in all analyzed samples. The exception was the endosperm expression-related element Skn-1, which negatively regulated expression in four tissues or treatments. Expression analysis showed that the expansin genes in Populus trichocarpa performed much differently under regular and abiotic stress conditions, which well matched the diversity of their promoter sequences. The results show that expansin genes play an important role in plant growth and development and stress resistance through expression adjustment. Full article

The abscission of fruits has a significant impact on yield, which in turn has a corresponding effect on economic benefits. In order to better understand the molecular mechanism of early coconut fruit abscission, the morphological and structural characteristics, cell wall hydrolysis and oxidase activities, phytohormones, and transcriptomes were analyzed in the abscission zone (AZ) from early-abscised coconut fruits (AFs) and non-abscised coconut fruits (CFs). These results indicated that the weight and water content of AFs are significantly lower than those of CFs, and the color of AFs is a grayish dark red, with an abnormal AZ structure. Cellulase (CEL), polygalacturonase (PG), pectinesterase (PE), and peroxidase (POD) activities were significantly lower than those of CFs. The levels of auxin (IAA), gibberellin (GA), cytokinins (CKs), and brassinosteroid (BR) in AFs were significantly lower than those in CFs. However, the content of abscisic acid (ABA), ethylene (ETH), jasmonic acid (JA), and salicylic acid (SA) in AFs was significantly higher than in CFs. The transcriptome analysis results showed that 3601 DEGs were functionally annotated, with 1813 DEGs upregulated and 1788 DEGs downregulated. Among these DEGs, many genes were enriched in pathways such as plant hormone signal transduction, carbon metabolism, peroxisome, pentose and gluconate interconversion, MAPK signaling pathway—plant, and starch and sucrose metabolism. Regarding cell wall remodeling-related genes (PG, CEL, PE, POD, xyloglucan endoglucosidase/hydrogenase (XTH), expansin (EXP), endoglucanase, chitinase, and beta-galactosidase) and phytohormone-related genes (IAA, GA, CKs, BR, ABA, JA, SA, and ETH) were significantly differentially expressed in the AZ of AFs. Additionally, BHLH, ERF/AP2, WRKY, bZIP, and NAC transcription factors (TFs) were significantly differently expressed, reflecting their crucial role in regulating the abscission process. This study’s results revealed the molecular mechanism of early fruit abscission in coconuts. This provided a new reference point for further research on coconut organ development and abscission. Full article

Expansin is a cell wall relaxant protein that is common in plants and directly or indirectly participates in the whole process of plant root growth, development and morphogenesis. A well-developed root system helps plants to better absorb water and nutrients from the soil while effectively assisting them in resisting osmotic stress, such as salt stress. In this study, we observed and quantified the morphology of the roots of Arabidopsis overexpressing the TaEXPAs gene obtained by the research group in the early stage of development. We combined the bioinformatics analysis results relating to EXPA genes in five plants and identified TaEXPA7-B, a member of the EXPA family closely related to root development in winter wheat. Subcellular localization analysis of the TaEXPA7-B protein showed that it is located in the plant cell wall. In this study, the TaEXPA7-B gene was overexpressed in rice. The results showed that plant height, root length and the number of lateral roots of rice overexpressing the TaEXPA7-B gene were significantly higher than those of the wild type, and the expression of the TaEXPA7-B gene significantly promoted the growth of lateral root primordium and cortical cells. The plants were treated with 250 mM NaCl solution to simulate salt stress. The results showed that the accumulation of osmotic regulators, cell wall-related substances and the antioxidant enzyme activities of the overexpressed plants were higher than those of the wild type, and they had better salt tolerance. This paper discusses the effects of winter wheat expansins in plant root development and salt stress tolerance and provides a theoretical basis and relevant reference for screening high-quality expansin regulating root development and salt stress resistance in winter wheat and its application in crop molecular breeding. Full article

Poplar coma, the fluff-like appendages of seeds originating from the differentiated surface cells of the placenta and funicle, aids in the long-distance dispersal of seeds in the spring. However, it also poses hazards to human safety and causes pollution in the surrounding environment. Unraveling the regulatory mechanisms governing the initiation and development of coma is essential for addressing this issue comprehensively. In this study, strand-specific RNA-seq was conducted at three distinct stages of coma development, revealing 1888 lncRNAs and 52,810 mRNAs. The expression profiles of lncRNAs and mRNAs during coma development were analyzed. Subsequently, potential target genes of lncRNAs were predicted through co-localization and co-expression analyses. Integrating various types of sequencing data, lncRNA-miRNA-TF regulatory networks related to the initiation of coma were constructed. Utilizing identified differentially expressed genes encoding kinesin and actin, lncRNA-miRNA-mRNA regulatory networks associated with the construction and arrangement of the coma cytoskeleton were established. Additionally, relying on differentially expressed genes encoding cellulose synthase, sucrose synthase, and expansin, lncRNA-miRNA-mRNA regulatory networks related to coma cell wall synthesis and remodeling were developed. This study not only enhances the comprehension of lncRNA but also provides novel insights into the molecular mechanisms governing the initiation and development of poplar coma. Full article

As a type of cell-wall-relaxing protein that is widely present in plants, expansins have been shown to actively participate in the regulation of plant growth and responses to environmental stress. Wild soybeans have long existed in the wild environment and possess abundant resistance gene resources, which hold significant value for the improvement of cultivated soybean germplasm. In our previous study, we found that the wild soybean expansin gene GsEXLB14 is specifically transcribed in roots, and its transcription level significantly increases under salt and drought stress. To further identify the function of GsEXLB14, in this study, we cloned the CDS sequence of this gene. The transcription pattern of GsEXLB14 in the roots of wild soybean under salt and drought stress was analyzed by qRT-PCR. Using an Agrobacterium rhizogenes-mediated genetic transformation, we obtained soybean hairy roots overexpressing GsEXLB14. Under 150 mM NaCl- and 100 mM mannitol-simulated drought stress, the relative growth values of the number, length, and weight of transgenic soybean hairy roots were significantly higher than those of the control group. We obtained the transcriptomes of transgenic and wild-type soybean hairy roots under normal growth conditions and under salt and drought stress through RNA sequencing. A transcriptomic analysis showed that the transcription of genes encoding expansins (EXPB family), peroxidase, H⁺-transporting ATPase, and other genes was significantly upregulated in transgenic hairy roots under salt stress. Under drought stress, the transcription of expansin (EXPB/LB family) genes increased in transgenic hairy roots. In addition, the transcription of genes encoding peroxidases, calcium/calmodulin-dependent protein kinases, and dehydration-responsive proteins increased significantly. The results of qRT-PCR also confirmed that the transcription pattern of the above genes was consistent with the transcriptome. The differences in the transcript levels of the above genes may be the potential reason for the strong tolerance of soybean hairy roots overexpressing the GsEXLB14 gene under salt and drought stress. In conclusion, the expansin GsEXLB14 can be used as a valuable candidate gene for the molecular breeding of soybeans. Full article

Expansins, a class of cell-wall-loosening proteins that regulate plant growth and stress resistance, have been studied in a variety of plant species. However, little is known about the Expansins present in alfalfa (Medicago sativa L.) due to the complexity of its tetraploidy. Based on the alfalfa (cultivar “XinjiangDaye”) reference genome, we identified 168 Expansin members (MsEXPs). Phylogenetic analysis showed that MsEXPs consist of four subfamilies: MsEXPAs (123), MsEXPBs (25), MsEXLAs (2), and MsEXLBs (18). MsEXPAs, which account for 73.2% of MsEXPs, and are divided into twelve groups (EXPA-I–EXPA-XII). Of these, EXPA-XI members are specific to Medicago trunctula and alfalfa. Gene composition analysis revealed that the members of each individual subfamily shared a similar structure. Interestingly, about 56.3% of the cis-acting elements were predicted to be associated with abiotic stress, and the majority were MYB- and MYC-binding motifs, accounting for 33.9% and 36.0%, respectively. Our short-term treatment (≤24 h) with NaCl (200 mM) or PEG (polyethylene glycol, 15%) showed that the transcriptional levels of 12 MsEXPs in seedlings were significantly altered at the tested time point(s), indicating that MsEXPs are osmotic-responsive. These findings imply the potential functions of MsEXPs in alfalfa adaptation to high salinity and/or drought. Future studies on MsEXP expression profiles under long-term (>24 h) stress treatment would provide valuable information on their involvement in the response of alfalfa to abiotic stress. Full article

Pumpkin (Cucurbita maxima) is an important vegetable crop of the Cucurbitaceae plant family. The fruits of pumpkin are often used as directly edible food or raw material for a number of processed foods. In nature, mature pumpkin fruits differ in size, shape, and color. The Atlantic Giant (AG) cultivar has the world’s largest fruits and is described as the giant pumpkin. AG is well-known for its large and bright-colored fruits with high ornamental and economic value. At present, there are insufficient studies that have focused on the formation factors of the AG cultivar. To address these knowledge gaps, we performed comparative transcriptome, proteome, and metabolome analysis of fruits from the AG cultivar and a pumpkin with relatively small fruit (Hubbard). The results indicate that up-regulation of gene-encoded expansins contributed to fruit cell expansion, and the increased presence of photoassimilates (stachyose and D-glucose) and jasmonic acid (JA) accumulation worked together in terms of the formation of large fruit in the AG cultivar. Notably, perhaps due to the rapid transport of photoassimilates, abundant stachyose that was not converted into glucose in time was detected in giant pumpkin fruits, implying that a unique mode of assimilate unloading is in existence in the AG cultivar. The potential molecular regulatory network of photoassimilate metabolism closely related to pumpkin fruit expansion was also investigated, finding that three MYB transcription factors, namely CmaCh02G015900, CmaCh01G018100, and CmaCh06G011110, may be involved in metabolic regulation. In addition, neoxanthin (a type of carotenoid) exhibited decreased accumulation that was attributed to the down-regulation of carotenoid biosynthesis genes in AG fruits, which may lead to pigmentation differences between the two pumpkin cultivars. Our current work will provide new insights into the potential formation factors of giant pumpkins for further systematic elucidation. Full article

Arbuscular mycorrhizal fungi (AMF) are known to enhance plant growth via stimulation of root system development. However, the extent of their effects and underlying mechanisms across different citrus genotypes remain to be fully elucidated. This study investigates the impact of Funneliformis mosseae (F. mosseae) inoculation on plant growth performance, root morphology, phosphorus (P), and indole-3-acetic acid (IAA) concentrations, as well as the expression of related synthesis and transporter genes in three citrus genotypes: red tangerine (Citrus tangerine ex. Tanaka), kumquat (Fortunella margarita L. Swingle), and fragrant citrus (Citrus junos Sieb. ex. Tanaka). Following 12 weeks of inoculation, significant improvements were observed in plant height, shoot and root biomass, total root length, average root diameter, second-order lateral root development, root hair density, and root hair length across all genotypes. Additionally, F. mosseae inoculation significantly increased root P and IAA concentrations in the three citrus genotypes. Notably, phosphatase activity was enhanced in F. margarita but reduced in C. tangerine and C. junos following inoculation. Gene expression analysis revealed a universal upregulation of the P transporter gene PT5, whereas expressions of the auxin synthesis gene YUC2, transporter gene LAX2, and phosphatase gene PAP1 were commonly downregulated. Specific to genotypes, expressions of YUC5, LAX5, PIN2, PIN3, PIN6, and expansin genes EXPA2 and EXPA4 were significantly upregulated in C. tangerine but downregulated in F. margarita and C. junos. Principal component analysis and correlation assessments highlighted a strong positive association between P concentration, P and auxin synthesis, and transporter gene expressions with most root morphology traits, except for root average diameter. Conversely, IAA content and phosphatase activities were negatively correlated with these root traits. These findings suggest that F. mosseae colonization notably enhances plant growth and root system architecture in citrus genotypes via modifications in P transport and IAA accumulation, indicating a complex interplay between mycorrhizal symbiosis and host plant physiology. Full article

Expansins (EXPs) loosen plant cell walls and are involved in diverse developmental processes through modifying cell-walls; however, little is known about the role of PpEXPs in peach fruit. In this study, 26 PpEXP genes were identified in the peach genome and grouped into four subfamilies, with 20 PpEXPAs, three PpEXPBs, one PpEXPLA and two PpEXPLBs. The 26 PpEXPs were mapped on eight chromosomes. The primary mode of gene duplication of the PpEXPs was dispersed gene duplication (DSD, 50%). Notably, cis-elements involved in light responsiveness and MeJA-responsiveness were detected in the promoter regions of all PpEXPs, while ethylene responsive elements were observed in 12 PpEXPs. Transcript profiling of PpEXPs in the peach fruit varieties of MF (melting), NMF (non-melting) and SH (stony hard) at different stages showed that PpEXPs displayed distinct expression patterns. Among the 26 PpEXPs, 15 PpEXPs were expressed in the fruit. Combining the expressing patterns of PpEXPs in fruits with different flesh textures, PpEXPA7, PpEXPA13 and PpEXPA15 were selected as candidate genes, as they were highly consistent with the patterns of previous reported key genes (PpPGM, PpPGF and PpYUC11) in regard to peach fruit texture. The genes with different expression patterns between MF and NMF were divided into 16 modules, of which one module, with pink and midnightblue, negatively correlated with the phenotype of fruit firmness and was identified as PpEXPA1 and PpEXPA7, while the other module was identified as PpERF in the pink module, which might potentially effect fruit texture development by regulating PpEXPs. These results provide a foundation for the functional characterization of PpEXPs in peach. Full article

Seed weight is an important target trait in pomegranate breeding and culture. Expansins act by loosening plant cell walls and cellulosic materials, permitting turgor-driven cell enlargement. However, the role of expansin genes (EXPs) in pomegranate seed weight remains elusive. A total of 29 PgrEXPs were identified in the ‘Dabenzi’ genome. These genes were classified into four subfamilies and 14 subgroups, including 22 PgrEXPAs, 5 PgrEXPBs, 1 PgrEXPLA, and 1 PgrEXPLB. Transcriptome analysis of PgrEXPs in different tissues (root, leaf, flower, peel, and seed testa) in ‘Dabenzi’, and the seed testa of the hard-seeded pomegranate cultivar ‘Dabenzi’ and soft-seeded cultivar ‘Tunisia’ at three development stages showed that three PgrEXPs (PgrEXPA11, PgrEXPA22, PgrEXPA6) were highly expressed throughout seed development, especially in the sarcotesta. SNP/Indel markers of these PgrEXPs were developed and used to genotype 101 pomegranate accessions. The association of polymorphic PgrEXPs with seed weight-related traits (100-seed weight, 100-kernel weight, 100-sarcotesta weight, and the percentage of 100-sarcotesta to 100-seed weight) were analyzed. PgrEXP22 was significantly associated with 100-seed weight and 100-sarcotesta weight and is a likely candidate for regulating seed weight and sarcotesta development in particular. This study provides an effective tool for the genetic improvement of seed weight in pomegranate breeding programs. Full article

Improving fruit size or weight, firmness, and shelf life is a major target for horticultural crop breeding. It is associated with the depolymerization and rearrangement of cell components, including pectin, hemicellulose, cellulose, and other structural (glyco)proteins. Expansins are structural proteins to loosen plant cell wall polysaccharides in a pH-dependent manner and play pivotal roles in the process of fruit development, ripening, and softening. Rubus chingii Hu, a unique Chinese red raspberry, is a prestigious pharmaceutical and nutraceutical dual-function food with great economic value. Thirty-three RchEXPs were predicted by genome-wide identification in this study, containing twenty-seven α-expansins (EXPAs), three β-expansins (EXPBs), one expansin-like A (EXPLA), and two expansin-like B (EXPLBs). Subsequently, molecular characteristics, gene structure and motif compositions, phylogenetic relationships, chromosomal location, collinearity, and regulatory elements were further profiled. Furthermore, transcriptome sequencing (RNA-seq) and real-time quantitative PCR assays of fruits from different developmental stages and lineages showed that the group of RchEXPA5, RchEXPA7, and RchEXPA15 were synergistically involved in fruit expanding and ripening, while another group of RchEXPA6 and RchEXPA26 might be essential for fruit ripening and softening. They were regulated by both abscisic acid and ethylene and were collinear with phylogenetic relationships in the same group. Our new findings laid the molecular foundation for improving the fruit texture and shelf life of R. chingii medicinal and edible fruit. Full article

Primulina serrulata is a valuable ornamental herb with rosette leaves and vibrant flowers. Some leaves of this species exhibit a bright and distinct white color along the upper veins, enhancing their ornamental value, while others are less white or entirely green. This variation is observed in adult leaves from natural habitats and among young leaves from seedlings grown in the laboratory. TMT-labeled proteomics technology was used to study the protein-level biogenesis of white-veined (WV) P. serrulata leaves. Our objective was to offer novel insight into the breeding of WV plants. Chlorophyll (Chl) content was significantly lower in the WV group than in the control group. Out of 6261 proteins identified, a mere 69 met the criteria for differentially expressed proteins (DEPs) after stringent screening for subsequent analyses. Among these DEPs, there were 44 proteins that exhibited downregulation and 25 that were upregulated in the WV plants. Some DEPs associated with chloroplasts and Chl biosynthesis were downregulated, leading to the absence of green coloration. Concurrently, Gene Ontology enrichment analysis further emphasized an insufficiency of magnesium, the key element in Chl biosynthesis. Many DEPs associated with abiotic or biotic stressors were downregulated, suggesting an overall weakening of stress resistance with certain compensatory mechanisms. Similarly, many DEPs related to modifying biomacromolecules were downregulated, possibly affected by the decrease in proteins involved in photosynthesis and stress resistance. Some DEPs containing iron were upregulated, indicating that iron is mainly used to synthesize heme and ferritin rather than Chl. Additionally, several DEPs related to sulfur or sulfate were upregulated, suggesting strengthened respiration. Expansin-A4 and pectinesterase were upregulated, coinciding with the emergence of a rough and bright surface in the white area of leaves, indicative of the elongation and gelation processes in the cell walls. These findings provide new insight for future studies to explore the mechanism of color formation in WV leaves. Full article

A novel cellulose microfibril swelling (Cms) gene of Bacillus sp. AY8 was successfully cloned and sequenced using a set of primers designed based on the conserved region of the gene from the genomic database. The molecular cloning of the Cms gene revealed that the gene consisted of 679 bp sequences encoding 225 amino acids. Further in silico analysis unveiled that the Cms gene contained the NlpC/P60 conserved region that exhibited a homology of 98% with the NlpC/P60 family proteins found in both the strains, Burkholderialata sp. and Burkholderia vietnamiensis. The recombinant Cms enzyme had a significant impact on the reduction of crystallinity indices (CrI) of various substrates including a 3%, a 3.97%, a 4.66%, and a substantial 14.07% for filter paper, defatted cotton fiber, avicel, and alpha cellulose, respectively. Additionally, notable changes in the spectral features were observed among the substrates treated with recombinant Cms enzymes compared to the untreated control. Specifically, there was a decrease in band intensities within the spectral regions of 3000–3450 cm⁻¹, 2900 cm⁻¹, 1429 cm⁻¹, and 1371 cm⁻¹ for the treated filter paper, cotton fiber, avicel, and alpha cellulose, respectively. Furthermore, the recombinant Cms enzyme exhibited a maximum cellulose swelling activity at a pH of 7.0 along with a temperature of 40 °C. The molecular docking data revealed that ligand molecules, such as cellobiose, dextrin, maltose 1-phosphate, and feruloyated xyloglucan, effectively bonded to the active site of the Cms enzyme. The molecular dynamics simulations of the Cms enzyme displayed stable interactions with cellobiose and dextrin molecules up to 100 ns. It is noteworthy to mention that the conserved region of the Cms enzyme did not match with those of the bioadditives like expansins and swollenin proteins. This study is the initial report of a bacterial cellulose microfibril swellase enzyme, which could potentially serve as an additive to enhance biofuel production by releasing fermentable sugars from cellulose. Full article