Drought is a common abiotic stress for terrestrial plants and often affects crop development and yield. Recent studies have suggested that lignin plays a crucial role in plant drought tolerance; however, the underlying molecular mechanisms are still largely unknown. Here, we report that the rice (Oryza sativa) gene CINNAMOYL-CoA REDUCTASE 10 (OsCCR10) is directly activated by the OsNAC5 transcription factor, which mediates drought tolerance through regulating lignin accumulation. CCR is the first committed enzyme in the monolignol synthesis pathway, and the expression of 26 CCR genes was observed to be induced in rice roots under drought. Subcellular localisation assays revealed that OsCCR10 is a catalytically active enzyme that is localised in the cytoplasm. The OsCCR10 transcript levels were found to increase in response to abiotic stresses, such as drought, high salinity, and abscisic acid (ABA), and transcripts were detected in roots at all developmental stages. In vitro enzyme activity and in vivo lignin composition assay suggested that OsCCR10 is involved in H- and G-lignin biosynthesis. Transgenic rice plants overexpressing OsCCR10 showed improved drought tolerance at the vegetative stages of growth, as well as higher photosynthetic efficiency, lower water loss rates, and higher lignin content in roots compared to non-transgenic (NT) controls. In contrast, CRISPR/Cas9-mediated OsCCR10 knock-out mutants exhibited reduced lignin accumulation in roots and less drought tolerance. Notably, transgenic rice plants with root-preferential overexpression of OsCCR10 exhibited higher grain yield than NT controls plants under field drought conditions, indicating that lignin biosynthesis mediated by OsCCR10 contributes to drought tolerance.

中文翻译：

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OsNAC5对水稻肉桂酰辅酶A还原酶10的转录激活，通过调节根中木质素的积累来促进耐旱性

干旱是陆生植物常见的非生物胁迫，经常影响作物发育和产量。最近的研究表明，木质素在植物耐旱性中起着至关重要的作用。然而，潜在的分子机制仍然很大程度上未知。在这里，我们报告了水稻 ( Oryza sativa ) 基因CINNAMOYL-CoA REDUCTASE 10 ( OsCCR10 ) 被 OsNAC5 直接激活转录因子，通过调节木质素积累来介导耐旱性。CCR 是木质素单体合成途径中的第一个定向酶，在干旱条件下，观察到 26 个 CCR 基因在水稻根系中被诱导表达。亚细胞定位分析表明，OsCCR10 是一种定位在细胞质中的催化活性酶。发现 OsCCR10转录物水平随着干旱、高盐度和脱落酸 (ABA) 等非生物胁迫而增加，并且在所有发育阶段的根中都检测到了转录物。体外酶活性和体内木质素组成测定表明，OsCCR10 参与了 H-和 G-木质素的生物合成。过表达的转基因水稻植物与非转基因 (NT) 对照相比， OsCCR10在生长的营养阶段表现出更高的耐旱性，以及更高的光合效率、更低的水分流失率和更高的根系木质素含量。相比之下，CRISPR/Cas9 介导的OsCCR10敲除突变体表现出根中木质素积累减少和耐旱性降低。值得注意的是，在田间干旱条件下，根优先过表达OsCCR10的转基因水稻比 NT 对照植物表现出更高的谷物产量，表明OsCCR10介导的木质素生物合成有助于耐旱。