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Cooperative functioning between phenylalanine ammonia lyase and isochorismate synthase activities contributes to salicylic acid biosynthesis in soybean
Author(s) -
Shine M. B.,
Yang JungWook,
ElHabbak Mohamed,
Nagyabhyru Padmaja,
Fu DaQi,
Navarre Duroy,
Ghabrial Said,
Kachroo Pradeep,
Kachroo Aardra
Publication year - 2016
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.14078
Subject(s) - phenylalanine ammonia lyase , pseudomonas syringae , salicylic acid , phytophthora sojae , arabidopsis , biosynthesis , biology , pathogen , phytophthora , plant defense against herbivory , lyase , biochemistry , plant disease resistance , systemic acquired resistance , arabidopsis thaliana , microbiology and biotechnology , phenylalanine , enzyme , gene , botany , amino acid , mutant
Summary Salicylic acid ( SA ), an essential regulator of plant defense, is derived from chorismate via either the phenylalanine ammonia lyase ( PAL ) or the isochorismate synthase ( ICS ) catalyzed steps. The ICS pathway is thought to be the primary contributor of defense‐related SA , at least in Arabidopsis. We investigated the relative contributions of PAL and ICS to defense‐related SA accumulation in soybean ( Glycine max ). Soybean plants silenced for five PAL isoforms or two ICS isoforms were analyzed for SA concentrations and SA ‐derived defense responses to the hemibiotrophic pathogens Pseudomonas syringae and Phytophthora sojae . We show that, unlike in Arabidopsis, PAL and ICS pathways are equally important for pathogen‐induced SA biosynthesis in soybean. Knock‐down of either pathway shuts down SA biosynthesis and abrogates pathogen resistance. Moreover, unlike in Arabidopsis, pathogen infection is associated with the suppression of ICS gene expression. Pathogen‐induced biosynthesis of SA via the PAL pathway correlates inversely with phenylalanine concentrations. Although infections with either virulent or avirulent strains of the pathogens increase SA concentrations, resistance protein‐mediated response to avirulent P. sojae strains may function in an SA ‐independent manner. These results show that PAL ‐ and ICS ‐catalyzed reactions function cooperatively in soybean defense and highlight the importance of PAL in pathogen‐induced SA biosynthesis.