State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing, China.
MARA Key Laboratory of Pest Monitoring and Green Management, Department of Plant Pathology, College of Plant Protection, China Agricultural University, Beijing, China.
PLoS Pathog. 2022 Dec 8;18(12):e1011036. doi: 10.1371/journal.ppat.1011036. eCollection 2022 Dec.
Serine/arginine-rich (SR) proteins are well known as splicing factors in humans, model animals and plants. However, they are largely unknown in regulating pre-mRNA splicing of filamentous fungi. Here we report that the SR protein MoSrp1 enhances and suppresses alternative splicing in a model fungal plant pathogen Magnaporthe oryzae. Deletion of MoSRP1 caused multiple defects, including reduced virulence and thousands of aberrant alternative splicing events in mycelia, most of which were suppressed or enhanced intron splicing. A GUAG consensus bound by MoSrp1 was identified in more than 94% of the intron or/and proximate exons having the aberrant splicing. The dual functions of regulating alternative splicing of MoSrp1 were exemplified in enhancing and suppressing the consensus-mediated efficient splicing of the introns in MoATF1 and MoMTP1, respectively, which both were important for mycelial growth, conidiation, and virulence. Interestingly, MoSrp1 had a conserved sumoylation site that was essential to nuclear localization and enhancing GUAG binding. Further, we showed that MoSrp1 interacted with a splicing factor and two components of the exon-joining complex via its N-terminal RNA recognition domain, which was required to regulate mycelial growth, development and virulence. In contrast, the C-terminus was important only for virulence and stress responses but not for mycelial growth and development. In addition, only orthologues from Pezizomycotina species could completely rescue defects of the deletion mutants. This study reveals that the fungal conserved SR protein Srp1 regulates alternative splicing in a unique manner.
丝氨酸/精氨酸丰富（SR）蛋白是人类、模式动物和植物中剪接因子的重要组成部分。然而，它们在丝状真菌中调控前体 mRNA 剪接的功能在很大程度上尚不清楚。本研究报道了 SR 蛋白 MoSrp1 增强和抑制稻瘟病菌（Magnaporthe oryzae）中可变剪接的作用。MoSRP1 缺失导致多种缺陷，包括毒力降低和菌丝中出现数千个异常可变剪接事件，其中大多数被抑制或增强内含子剪接。在超过 94%具有异常剪接的内含子或/和近邻外显子中，鉴定到由 MoSrp1 结合的 GUAG 共识序列。MoSrp1 调节可变剪接的双重功能在增强和抑制 MoATF1 和 MoMTP1 中内含子的保守介导有效剪接中得到了例证，这两个内含子对于菌丝生长、产孢和毒力都很重要。有趣的是，MoSrp1 具有一个保守的 SUMO 化位点，对于核定位和增强 GUAG 结合是必需的。此外，我们还表明 MoSrp1 通过其 N 端 RNA 识别结构域与剪接因子和外显子连接复合物的两个组件相互作用，这对于调节菌丝生长、发育和毒力是必需的。相比之下，C 端仅对毒力和应激反应很重要，但对菌丝生长和发育不重要。此外，只有 Pezizomycotina 种系的同源物才能完全挽救缺失突变体的缺陷。本研究揭示了真菌保守的 SR 蛋白 Srp1 以独特的方式调节可变剪接。
