Comparative analysis of miRNA expression profiles in flowering and non-flowering tissue of Crocus sativus L.

Crocus sativus is a valuable plant due to the presence of apocarotenoids in its stigma. Considerable work has been done in the past to understand the apocarotenoid biosynthetic pathway in saffron. However, the reports on understanding the regulation of flowering at the post-transcriptional level are meagre. The study aimed to discover the candidate miRNAs, target genes, transcription factors (TFs), and apocarotenoid biosynthetic pathway genes associated with the regulation and transition of flowering in C. sativus. In the present investigation, miRNA profiling was performed in flowering and non-flowering corms of saffron, along with expression analysis of apocarotenoid genes and transcription factors involved in the synthesis of secondary metabolites. Significant modulation in the expression of miR156, miR159, miR166, miR172, miR395, miR396, miR399, and miR408 gene families was observed. We obtained 36 known miRNAs (26 in flowering and 10 in non-flowering) and 64 novel miRNAs (40 in flowering and 24 in non-flowering) unique to specific tissues in our analysis. TFs, including CsMADS and CsMYb, showed significant modulation in expression in flowering tissue, followed by CsHB. Additionally, the miRNAs were predicted to be involved in carbohydrate metabolism, phytohormone signalling, regulation of flower development, and response to stress, cold, and defence. The comprehensive study has enhanced our understanding of the regulatory machinery comprising factors like phytohormones, abiotic stress, apocarotenoid genes, transcription factors, and miRNAs responsible for the synthesis of apocarotenoids and developmental processes during and after flowering.