Abstract
BackgroundSalt stress and bacterial blight caused by Xanthomonas oryzae pv. oryzae (Xoo) are key limiting factors of rice (Oryza sativa L.) yields. Members of sucrose non-fermenting 1 (SNF1)-related protein kinase 2 (SnRK2), which is a family of plant-specific Ser/Thr kinases, are important components of signaling pathways involved in plant developmental processes and responses to stresses. There are 10 members of the SnRK2 family in rice; however, their functions are poorly understood, as are the underlying molecular mechanisms.ResultsIn this study, we found that OsSAPK9, which belongs to the SnRK2 family, positively regulated salt-stress tolerance and strain-specific resistance to bacterial blight in rice. RNA sequencing revealed that there were 404 and 1324 genes differentially expressed in OsSAPK9-RNAi in comparison with wild-type plants under salt-stress conditions and after Xoo inoculation, respectively, which participate in basic metabolic processes. In total, 65 common differentially expressed genes involved mainly in defense responses were detected both under salt-stress conditions and after Xoo inoculation. Moreover, in vivo and in vitro experiments demonstrated that OsSAPK9 forms a protein complex with the molecular chaperones OsSGT1 and OsHsp90, and transgenic plants overexpressing OsSGT1 exhibited decreased tolerances to salt stress and significantly increased resistance levels to bacterial blight. Thus, OsSAPK9 may function as a center node regulator of salt-stress responses and disease-resistance pathways through its interaction with OsSGT1 in rice.ConclusionThis study confirms that OsSAPK9 functions as a positive regulator of salt-stress responses and disease resistance through its interaction with OsSGT1 in rice.
Highlights
Salt stress and bacterial blight caused by Xanthomonas oryzae pv. oryzae (Xoo) are key limiting factors of rice (Oryza sativa L.) yields
OsSAPK9-OE lines OE1 and OE2 were more tolerant to the salt treatment, and their survival rates significantly increased in comparison with the WT (Fig. 1b, g)
When plants were treated with NaCl, the MDA contents were significantly higher in the OsSAPK9-RNAi than in the WT plants and significantly lower in OsSAPK9-OE plants than in the WT plants (Fig. 1d, h)
Summary
Salt stress and bacterial blight caused by Xanthomonas oryzae pv. oryzae (Xoo) are key limiting factors of rice (Oryza sativa L.) yields. Salt stress and bacterial blight caused by Xanthomonas oryzae pv. There are 10 members of the SnRK2 family in rice; their functions are poorly understood, as are the underlying molecular mechanisms. The overexpression of OsSAPK4 increases the tolerance to oxidative stresses (Diédhiou et al 2008), while the overexpression SAPK9 from Oryza rufipogon in a drought-sensitive rice line enhances drought tolerance and yield-related traits (Dey et al 2016). While OsSAPKs might be associated with responses to abiotic and biotic stresses in rice, the functions of this gene family are poorly understood and their underlying molecular mechanisms have yet to be elucidated. We used OsSAPK9-RNAi and OsSAPK9overexpression transgenic lines to show that OsSAPK9 is involved in tolerance to salt stress and resistance to bacterial blight. We used transcriptome profiling to investigate the defense responses to salt stress and Xoo infection mediated by OsSAPK9
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