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Chitin Elicitor-Responsive Photon Emission is potentiated by Plant Activators through Priming of Salicylic Acid Signaling via OsWRKY45 in Rice

Hiroyuki Iyozumi*, Hideki Nukui and Kimihiko Kato

Priming of plant cells for faster and enhanced defense responses against pathogen attacks is a common feature of chemically or biologically induced resistance. The authors previously developed a priming detection system that detects priming as potentiation of chitin elicitor-responsive photon emission (C-ERPE) in rice cells pretreated with various types of chemical inducers of disease resistance, called plant activators. To elucidate the mechanisms underlying C-ERPE potentiation, the authors performed gene knockdown of OsWRKY45, a major regulator of salicylic acid (SA)-dependent defense responses in rice, and estimated the effects of SA isomers on C-ERPE potentiation. Plant activators induced a 200-300% increase in C-ERPE in the wild type, whereas OsWRKY45 knockdown attenuated the increase in C-ERPE to less than 60%. Native SA induced more than a 150% increase in C-ERPE, but structural isomers of SA were less effective (10-24% increase). These SA signaling-disruption experiments indicate that the potentiation of C-ERPE requires intrinsic components of hormonal signaling for defense, at least for priming by inducers of systemic acquired resistance.