The prevailing reaction of plants to pest attack is the activation of various defense mechanisms. In tomato, several studies indicate that an 18 amino acid (aa) peptide, called systemin, is a primary signal for the systemic induction of direct resistance against plant-chewing pests, and that the transgenic expression of the prosystemin gene (encoding the 200 aa systemin precursor) activates genes involved in the plant response to herbivores. By using a combination of behavioral, chemical, and gene expression analyses, we report that systemin enhances the production of bioactive volatile compounds, increases plant attractivity towards parasitiod wasps, and activates genes involved in volatile production. Our data imply that systemin is involved in the systemic activation of indirect defense in tomato, and we conclude that a single gene controls the systemic activation of coordinated and associated responses against pests.
A family of CBF transcription factors plays a major role in reconfiguring the plant transcriptome in response to low-freezing temperature in temperate cereals. In barley, more than 13 HvCBF genes map coincident with the major QTL FR-H2 suggesting them as candidates to explain the function of the locus. Variation in copy number (CNV) of specific HvCBFs was assayed in a panel of 41 barley genotypes using RT-qPCR. Taking advantage of an accurate phenotyping that combined Fv/Fm and field survival, resistance-associated variants within FR-H2 were identified. Genotypes with an increased copy number of HvCBF4 and HvCBF2 (at least ten and eight copies, respectively) showed greater frost resistance. A CAPS marker able to distinguish the CBF2A, CBF2B and CBF2A/B forms was developed and showed that all the higher-ranking genotypes in term of resistance harbour only CBF2A, while other resistant winter genotypes harbour also CBF2B, although at a lower CNV. In addition to the major involvement of the HvCBF4-HvCBF2 genomic segment in the proximal cluster of CBF elements, a negative role of HvCBF3 in the distal cluster was identified. Multiple linear regression models taking into account allelic variation at FR-H1/VRN-H1 explained 0.434 and 0.550 (both at p < 0.001) of the phenotypic variation for Fv/Fm and field survival respectively, while no interaction effect between CNV at the HvCBFs and FR-H1/VRN-H1 was found. Altogether our data suggest a major involvement of the CBF genes located in the proximal cluster, with no apparent involvement of the central cluster contrary to what was reported for wheat
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