Increasing drought stress poses a severe threat to agricultural productivity. Plants, however, evolved numerous mechanisms to cope with such environmental stress. Here we report that the stress-induced production of a peptide signal contributes to stress tolerance. The expression of phytosulfokine (PSK) peptide precursor genes, and transcripts of three subtilisin-like serine proteases, SBT1.4, SBT3.7 and SBT3.8 were found to be up-regulated in response to osmotic stress. Stress symptoms were enhanced in sbt3.8 loss-of-function mutants and could be alleviated by PSK treatment. Osmotic stress tolerance was improved in plants overexpression the precursor of PSK1 (proPSK1) or SBT3.8 resulting in higher fresh weight and improved lateral root development in the transgenic compared to wild-type plants. We further showed that SBT3.8 is involved in the biogenesis of the bioactive PSK peptide. ProPSK1 was cleaved by SBT3.8 at the C-terminus of the PSK pentapeptide. Processing by SBT3.8 depended on the aspartic acid residue adjacent to the cleavage site. ProPSK1 processing was impaired in the sbt3.8 mutant. The data suggest that increased expression in response to osmotic stress followed by the post-translational processing of proPSK1 by SBT3.8 leads to the production of PSK as a peptide signal for stress mitigation.

中文翻译：

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SBT3.8的前体加工和植物硫代信号传导有助于拟南芥的干旱胁迫耐受性

不断增加的干旱压力严重威胁着农业生产力。然而，植物进化出许多机制来应对这种环境压力。在这里我们报告说，应力诱导的肽信号产生有助于胁迫耐受性。发现植物硫代激酶（PSK）肽前体基因的表达以及三种枯草杆菌蛋白酶样丝氨酸蛋白酶SBT1.4，SBT3.7和SBT3.8的转录均响应渗透胁迫而上调。sbt3.8功能丧失的突变体的应激症状得到增强，可以通过PSK治疗得到缓解。与野生型植物相比，过表达PSK1（proPSK1）或SBT3.8的前体的植物的渗透胁迫耐受性得到改善，导致转基因中的鲜重更高，侧根发育得到改善。我们进一步证明了SBT3。图8涉及生物活性PSK肽的生物发生。ProPSK1在PSK五肽的C末端被SBT3.8切割。SBT3.8的加工取决于邻近切割位点的天冬氨酸残基。sbt3.8突变体中ProPSK1的加工受到损害。数据表明响应于渗透压力而增加的表达，然后由SBT3.8对proPSK1进行翻译后加工，导致产生PSK作为缓解压力的肽信号。