Wang Fan, Li Yang, Yuan Jianbo, Li Cong, Lin Yan, Gu Jinbao, Wang Zhen-Yu
School of Tropical Agriculture and Forestry, Hainan University, Haikou 570228, Hainan, China.
Institute of Nanfan and Seed Industry, Guangdong Academy of Sciences, Guangzhou 510316, Guangdong, China.
Plant Physiol. 2024 Oct 1;196(2):1126-1146. doi: 10.1093/plphys/kiae389.
Alternative splicing (AS) is an important posttranscriptional regulatory mechanism that improves plant tolerance to drought stress by modulating gene expression and generating proteome diversity. The interaction between the 5' end of U1 small nuclear RNA (U1 snRNA) and the conserved 5' splice site of precursor messenger RNA (pre-mRNA) is pivotal for U1 snRNP involvement in AS. However, the roles of U1 snRNA in drought stress responses remain unclear. This study provides a comprehensive analysis of AtU1 snRNA in Arabidopsis (Arabidopsis thaliana), revealing its high conservation at the 5' end and a distinctive four-leaf clover structure. AtU1 snRNA is localized in the nucleus and expressed in various tissues, with prominent expression in young floral buds, flowers, and siliques. The overexpression of AtU1 snRNA confers enhanced abiotic stress tolerance, as evidenced in seedlings by longer seedling primary root length, increased fresh weight, and a higher greening rate compared with the wild-type. Mature AtU1 snRNA overexpressor plants exhibit higher survival rates and lower water loss rates under drought stress, accompanied by a significant decrease in H2O2 and an increase in proline. This study also provides evidence of altered expression levels of drought-related genes in AtU1 snRNA overexpressor or genome-edited lines, reinforcing the crucial role of AtU1 snRNA in drought stress responses. Furthermore, the overexpression of AtU1 snRNA influences the splicing of downstream target genes, with a notable impact on SPEECHLESS (SPCH), a gene associated with stomatal development, potentially explaining the observed decrease in stomatal aperture and density. These findings elucidate the critical role of U1 snRNA as an AS regulator in enhancing drought stress tolerance in plants, contributing to a deeper understanding of the AS pathway in drought tolerance and increasing awareness of the molecular network governing drought tolerance in plants.
可变剪接（AS）是一种重要的转录后调控机制，通过调节基因表达和产生蛋白质组多样性来提高植物对干旱胁迫的耐受性。U1小核RNA（U1 snRNA）的5'端与前体信使RNA（pre-mRNA）保守的5'剪接位点之间的相互作用对于U1 snRNP参与可变剪接至关重要。然而，U1 snRNA在干旱胁迫响应中的作用仍不清楚。本研究对拟南芥中的AtU1 snRNA进行了全面分析，揭示了其5'端的高度保守性和独特的四叶草结构。AtU1 snRNA定位于细胞核中，并在各种组织中表达，在幼嫩花芽、花和角果中表达显著。AtU1 snRNA的过表达赋予了增强的非生物胁迫耐受性，与野生型相比，在幼苗中表现为更长的幼苗主根长度、增加的鲜重和更高的绿化率。成熟的AtU1 snRNA过表达植株在干旱胁迫下表现出更高的存活率和更低的失水率，同时过氧化氢显著减少，脯氨酸增加。本研究还提供了证据表明AtU1 snRNA过表达或基因组编辑系中干旱相关基因的表达水平发生了变化，强化了AtU1 snRNA在干旱胁迫响应中的关键作用。此外，AtU1 snRNA的过表达影响下游靶基因的剪接，对与气孔发育相关的基因SPEECHLESS（SPCH）有显著影响，这可能解释了观察到的气孔孔径和密度的降低。这些发现阐明了U1 snRNA作为可变剪接调节因子在增强植物干旱胁迫耐受性中的关键作用，有助于更深入地了解干旱耐受性中的可变剪接途径，并提高对植物干旱耐受性分子网络的认识。
