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

Abstract

Weeping lovegrass (Eragrostis curvula [Shrad.] Nees) is a perennial grass typicallyestablished in semi-arid regions, with good adaptability to dry conditions andsandy soils. This polymorphic complex includes both sexual and apomicticcytotypes, with different ploidy levels (2x-8x). Diploids are known to be sexual,while most polyploids are facultative apomicts, and full apomicts have also beenreported. Plant breeding studies throughout the years have focused on achievingthe introgression of apomixis into species of agricultural relevance, but, given thecomplexity of the trait, a deeper understanding of themolecular basis of regulatorymechanisms of apomixis is still required. Apomixis is thought to be associated withsilencing or disruption of the sexual pathway, and studies have shown it isinfluenced by epigenetic mechanisms. In a previous study, we explored the roleof miRNA-mRNA interactions using two contrasting E. curvula phenotypes. Here,the sexual OTA-S, the facultative Don Walter and the obligate apomicticTanganyika cDNA and sRNA libraries were inquired, searching for miRNAdiscovery and miRNA expression regulation of genes related to the reproductivemode. This allowed for the characterization of seven miRNAs and the validation oftheir miRNA-target interactions. Interestingly, a kinesin gene was found to berepressed in the apomictic cultivar Tanganyika, targeted by a novelmiRNA thatwasfound to be overexpressed in this genotype, suggestive of an involvement in thereproductive mode expression. Our work provided additional evidence of thecontribution of the epigenetic regulation of the apomictic pathway.