A. Capuzzo

ABSTRACT Plant calcium (Ca2+) signals are involved in a wide array of intracellular signaling pathways after pathogen invasion. Ca2+-binding sensory proteins such as Ca2+-dependent protein kinases (CDPKs) have been predicted to mediate the signaling following Ca2+ influx after pathogen infection. However, until now this prediction remains elusive. We conducted a genome-wide analysis of Malus x domestica CDPKs and identified 30 CDPK genes. Malus CDPKs were found to be similar to their counterparts in Arabidospis thaliana in gene...

ABSTRACT Upon herbivory, plants emit volatile organic compounds (VOCs) to attract herbivore’s predators. Emitted VOCs do not directly interfere with the herbivore, rather they are used by herbivores’ predator as a cue to locate their prey. The cascade of events involved in indirect defense starts from early signaling events such as intracellular Ca2+ variations, plasma membrane potential (Vm) depolarization and production of reactive oxygen species. This signaling pathways leads to the production of jasmonic acid (JA) from its precursor 12-oxophytodienoic acid (OPDA). Besides free JA, also conjugates with the amino acid isoleucine (JA-Ile), and probably other amino acids, are involved in signaling. JA and salicylic acid (SA) often act antagonistically and both are required for the induced response following herbivore feeding. The JA-related signaling pathway is involved in the production of herbivore-induced VOCs. In plants, intercellular connections are granted by plasmodesmata (PDs), plasma-membrane-lined channels that bridge the cell wall to achieve symplastic continuity. Since previous results have demonstrated that upon herbivore attack a strong Vm depolarization is generated at the bite zone and that an isotropic wave of Vm depolarization spreads throughout the entire attacked leaf, we argued whether PDs might be involved in this process. To test this hypothesis we analyzed by HS-SPME-GC/MS the herbivore-induced VOC emission of Arabidopsis wild type (WT) and Arabidopsis loss of PD-located proteins (PDLPs) function triple knockout plants (KO) by feeding experiments with the cotton harmyworm Spodoptera littoralis. We also evaluated by LC-ESI-MS/MS the JA, JA-Ile, SA, and OPDA content in control and herbivore wounded plants. VOC production was severely reduced in KO, when compared to WT. While no difference in OPDA were found between KO and WT, JA and JA-Ile were significantly reduced in the KO, which showed increased contents of SA.

ABSTRACT Neochloris oleoabundans is a green microalga known for the ability to increase its fatty acid (FA) content when grown under nitrogen (N) depletion. Accumulation of FAs and their composition were compared by cultivating N. oleoabundans in N limitation and N depletion conditions. We adopted an innovative approach that consists in semicontinuous cultivation mode as a strategy to optimize lipid accumulation. To identify the optimal conditions for the production of different FAs, a temporal profile of how different conditions may influence the microalgae culture in terms of biomass, FA concentration and composition was evaluated. N limited culture attained higher values of algal productivity and total FA concentration (0.42 mg L− 1 d− 1 and 91.2 mg L− 1) than N deplete culture (0.15 mg L− 1 d− 1 and 53.2 mg L− 1). Considering lipid accumulation, concentration and percentage of triacylglycerols (TAG) increased in all culture methods, with respect to the N replete control. In particular, N limitation led to a significant increase of polyunsaturated TAG (PUFA), while N depletion led to the highest level of monounsaturated TAG. These results suggest that N. oleoabundans biomass and FAs were strongly affected by the N supply and that the quality of the TAG fraction could be modulated in accordance to the utilization purpose in a wide range of applications. Semicontinuous culture resulted as a promising operational strategy for FAs production. More specifically, semicontinuous cultivation coupled to N limitation was found to be a convenient method to increment PUFA fraction and therefore to yield a high value product.