Cooperative functioning between phenylalanine ammonia lyase and isochorismate synthase activities contributes to salicylic acid biosynthesis in soybean

M. B. Shine, Jung Wook Yang, Mohamed El-Habbak, Padmaja Nagyabhyru, Da Qi Fu, Duroy Navarre, Said Ghabrial, Pradeep Kachroo, Aardra Kachroo

Research output: Contribution to journalArticlepeer-review

155 Scopus citations

Abstract

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.

Original languageEnglish
Pages (from-to)627-636
Number of pages10
JournalNew Phytologist
Volume212
Issue number3
DOIs
StatePublished - Nov 1 2016

Bibliographical note

Publisher Copyright:
© 2016 The Authors. New Phytologist © 2016 New Phytologist Trust

Keywords

  • isochorismate synthase (ICS)
  • pathogen defense
  • phenylalanine ammonia lyase (PAL)
  • salicylic acid (SA)
  • soybean (Glycine max)

ASJC Scopus subject areas

  • Physiology
  • Plant Science

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