Plants distinctively control green leaf volatile and jasmonate pathways, but some pathogens spike the plans
2017
Mwenda, C. M. | Mochizuki, S. | Matsui, K.
The oxylipin pathway is one of the signaling pathways employed by plants to ensure effective responses to biotic and abiotic challenges as well as developmental stimuli. Green leaf volatiles (GLVs) and jasmonates (JAs) are oxylipins derived from an oxidation reaction of fatty acids in plant cells, and are formed from fatty acids by a dioxygenation reaction catalyzed by lipoxygenases. GLVs and JAs have distinct physiological roles. GLVs are involved in direct and indirect plant defenses against herbivores and pathogens, whereas JAs function as signaling molecules in defense against mechanical wounding and attacks by herbivores and necrotrophic pathogens. Hydroperoxide lyase (HPL) and allene oxide synthase (AOS), which are related cytochrome P450s, designated CYP74A and 74B, respectively, are located downstream of lipoxygenase and separate the two branches. HPL and AOS metabolize a common fatty acid hydroperoxide substrate (13-hydroperoxide of linolenic acid) and, thus, they may compete for the same substrate. We recently reported that the spatiotemporal expression pattern of Arabidopsis thaliana HPL (AtHPL) after mechanical wounding was different from that of A. thaliana AOS (AtAOS). We hypothesized that each pathway is, in most cases, fine-tuned to avoid competition between HPL and AOS for the same substrate. However, the bacterial pathogen Pseudomonas syringae DC3000 corrupts this finely tuned system in A. thaliana.
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