Table_5_Dicer-Like Proteins Regulate Sexual Development via the Biogenesis of Perithecium-Specific MicroRNAs in a Plant Pathogenic Fungus Fusarium graminearum.XLSX

Ascospores act as the primary inoculum of Fusarium graminearum, which causes the destructive disease Fusarium head blight (FHB), or scab. MicroRNAs (miRNAs) have been reported in the F. graminearum vegetative stage, and Fgdcl2 is involved in microRNA-like RNA (milRNA) biogenesis but has no major impact on vegetative growth, abiotic stress or pathogenesis. In the present study, we found that ascospore discharge was decreased in the Fgdcl1 deletion mutant, and completely blocked in the double-deletion mutant of Fgdcl1 and Fgdcl2. Besides, more immature asci were observed in the double-deletion mutant. Interestingly, the up-regulated differentially expressed genes (DEGs) common to ΔFgdcl1 and ΔFgdcl1/2 were related to ion transmembrane transporter and membrane components. The combination of small RNA and transcriptome sequencing with bioinformatics analysis predicted 143 novel milRNAs in wild-type perithecia, and 138 of these milRNAs partly or absolutely depended on Fgdcl1, while only 5 novel milRNAs were still obtained in the Fgdcl1 and Fgdcl2 double-deletion mutant. Furthermore, 117 potential target genes were predicted. Overall, Fgdcl1 and Fgdcl2 genes were partly functionally redundant in ascospore discharge and perithecium-specific milRNA generation in F. graminearum, and these perithecium-specific milRNAs play potential roles in sexual development.

子囊孢子（Ascospores）是引起毁灭性病害赤霉病（Fusarium head blight, FHB，又称疮痂病）的禾谷镰孢菌（Fusarium graminearum）的主要初侵染源。此前已有研究在禾谷镰孢菌的营养生长阶段发现了微小RNA（miRNAs）；其中Fgdcl2参与类微小RNA（milRNA）的生物合成，但对该菌的营养生长、非生物胁迫响应及致病力无显著影响。本研究发现，Fgdcl1缺失突变体的子囊孢子弹射量显著降低，而Fgdcl1与Fgdcl2双缺失突变体的子囊孢子弹射则完全被阻断。此外，双缺失突变体中未成熟子囊的数量显著增多。值得注意的是，ΔFgdcl1与ΔFgdcl1/2中共同上调的差异表达基因（DEGs）主要与离子跨膜转运蛋白及膜组分相关。通过小分子RNA测序与转录组测序结合生物信息学分析，本研究在野生型子囊壳中预测得到143个新型类微小RNA；其中138个新型milRNA的生成部分或完全依赖于Fgdcl1，而在Fgdcl1与Fgdcl2双缺失突变体中仅能检测到5个新型milRNA。此外，本研究还预测得到117个潜在靶基因。综上，禾谷镰孢菌中Fgdcl1与Fgdcl2基因在子囊孢子弹射及子囊壳特异性milRNA生成过程中存在部分功能冗余，且这些子囊壳特异性milRNA可能在该菌的有性发育中发挥潜在作用。