A combined transcriptome - miRNAome approach revealed that a kinesin gene is differentially targeted by a novel miRNA in an apomictic genotype of Eragrostis curvula

Weeping lovegrass (Eragrostis curvula [Shrad.] Nees) is a perennial grass typically established in semi-arid regions, with good adaptability to dry conditions and sandy soils. This polymorphic complex includes both sexual and apomictic cytotypes, with different ploidy levels (2x-8x). Diploids are known to be sexual, while most polyploids are facultative apomicts, and full apomicts have also been reported. Plant breeding studies throughout the years have focused on achieving the introgression of apomixis into species of agricultural relevance, but, given the complexity of the trait, a deeper understanding of the molecular basis of regulatory mechanisms of apomixis is still required. Apomixis is thought to be associated with silencing or disruption of the sexual pathway, and studies have shown it is influenced by epigenetic mechanisms. In a previous study, we explored the role of miRNA-mRNA interactions using two contrasting E. curvula phenotypes. Here, the sexual OTA-S, the facultative Don Walter and the obligate apomictic Tanganyika cDNA and sRNA libraries were inquired, searching for miRNA discovery and miRNA expression regulation of genes related to the reproductive mode. This allowed for the characterization of seven miRNAs and the validation of their miRNA-target interactions. Interestingly, a kinesin gene was found to be repressed in the apomictic cultivar Tanganyika, targeted by a novel miRNA that was found to be overexpressed in this genotype, suggestive of an involvement in the reproductive mode expression. Our work provided additional evidence of the contribution of the epigenetic regulation of the apomictic pathway.弯叶画眉草（Eragrostis curvula [Shrad.] Nees）是一种多年生草本植物，通常定植于半干旱区域，对干旱环境与砂质土壤具有良好适应性。该多态复合体包含有性与无融合生殖（apomixis）两种细胞型，倍性水平涵盖2x至8x。已知二倍体为有性生殖型，多数多倍体为兼性无融合生殖体，另有研究报道了专性无融合生殖体。多年来的植物育种研究均致力于将无融合生殖性状渐渗至具有农业应用价值的物种中，但鉴于该性状的复杂性，目前仍需对无融合生殖调控机制的分子基础展开更深入的解析。无融合生殖被认为与有性通路的沉默或紊乱相关，已有研究表明其受表观遗传（epigenetic）机制调控。在先前的研究中，本团队利用两种表型差异显著的弯叶画眉草材料探究了微小RNA（microRNA，简称miRNA）与信使RNA（messenger RNA，简称mRNA）的互作调控作用。本次研究针对有性型材料OTA-S、兼性型材料Don Walter以及专性无融合生殖型材料Tanganyika的cDNA文库与小RNA（small RNA，简称sRNA）文库进行分析，以挖掘miRNA并解析生殖模式相关基因的miRNA表达调控规律。研究完成了7种miRNA的鉴定，并验证了其miRNA-靶基因互作关系。有趣的是，研究发现驱动蛋白基因（kinesin gene）在无融合生殖品种Tanganyika中受到抑制，该基因可被一种在该基因型中高表达的新型miRNA靶向调控，提示该互作通路参与生殖模式的表达调控。本研究为无融合生殖通路的表观遗传调控贡献提供了新的佐证。