Abstract
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.
Highlights
Plants, as sessile organisms, are continuously exposed to various environmental stresses in nature
WRKY45 is a central transcription factor that regulates strong defence signalling mediated by salicylic acid
We found that WRKY45 is activated through phosphorylation by a protein kinase, OsMPK6, which is activated by dual phosphorylation in response to the defence signalling
Summary
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 [1] [2]. Such tradeoffs between the responses to different stresses are often regulated by crosstalk between signalling pathways [3] [4] [5]. In Arabidopsis, NPR1, the transcriptional cofactor, plays a major role in the SA defence signalling pathway [8]. WRKY45 auto-regulates the transcription of its own gene [12] and is regulated by the ubiquitin-proteasome system [15]
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