Date Published: October 20, 2015
Publisher: Public Library of Science
Author(s): Yoshihisa Ueno, Riichiro Yoshida, Mitsuko Kishi-Kaboshi, Akane Matsushita, Chang-Jie Jiang, Shingo Goto, Akira Takahashi, Hirohiko Hirochika, Hiroshi Takatsuji, Sheng Yang He.
Plants, as sessile organisms, survive environmental changes by prioritizing their responses to the most life-threatening stress by allocating limited resources. Previous studies showed that pathogen resistance was suppressed under abiotic stresses. Here, we show the mechanism underlying this phenomenon. Phosphorylation of WRKY45, the central transcription factor in salicylic-acid (SA)-signalling-dependent pathogen defence in rice, via the OsMKK10-2–OsMPK6 cascade, was required to fully activate WRKY45. The activation of WRKY45 by benzothiadiazole (BTH) was reduced under low temperature and high salinity, probably through abscisic acid (ABA) signalling. An ABA treatment dephosphorylated/inactivated OsMPK6 via protein tyrosine phosphatases, OsPTP1/2, leading to the impaired activation of WRKY45 and a reduction in Magnaporthe oryzae resistance, even after BTH treatment. BTH induced a strong M. oryzae resistance in OsPTP1/2 knockdown rice, even under cold and high salinity, indicating that OsPTP1/2 is the node of SA-ABA signalling crosstalk and its down-regulation makes rice disease resistant, even under abiotic stresses. These results points to one of the directions to further improve crops by managing the tradeoffs between different stress responses of plants.
Plants, as sessile organisms, are continuously exposed to various environmental stresses in nature. To cope with such conditions using limited resources, plants have evolved various mechanisms that enable resource allocation to the most life-threatening stress  . Such tradeoffs between the responses to different stresses are often regulated by crosstalk between signalling pathways   . A number of studies have reported various signalling components that appear to influence signalling crosstalk. However, the precise molecular mechanisms that regulate the crosstalk remain poorly understood in most cases   .
Plants are constantly confronted to both abiotic and biotic stresses that seriously reduce their productivity. Plant responses to these stresses involve numerous complex physiological, molecular and cellular adaptations. When plants are simultaneously exposed to both abiotic and biotic stresses, plants respond in a specific manner depending on the interplays of signalling pathways that are invoked by respective stresses.