The effects of defects in multiple hormone signaling pathways on plant disease resistance

Abstract

Plants recognize pathogen attack by at least two distinct mechanisms and induce defense responses. One mechanism is for microbe-associated molecular patterns (MAMPs), such as flg22. We recently reported that flg22-induced resistance to a bacterial pathogen, Pseudomonas syringae pv. tomato DC3000 (PstDC3000) is partially dependent on SA signaling. Jasmonic (JA) acid and ethylene (ET) signaling are generally believed to inhibit SA signaling and negatively affect resistance against PstDC3000. We have explored the possibility that multiple signalings cooperatively contribute to the robust defense signaling network by constructing a dde2, ein2, pad4, sid2 quadruple mutant in which JA, ET and SA signaling are all blocked. Surprisingly, 80% of flg22-induced resistance was lost in the quadruple mutant. This result indicates that major parts of the resistance response are mediated by a signaling network controlled by these four genes and that JA/ET, as well as SA signaling, positively contribute to resistance against PstDC3000.