Transcriptome analysis of apical meristem enriched bud samples for size dependent flowering commitment in Crocus sativus reveal role of sugar and auxin signalling

Abstract

Background Cultivation of Crocus sativus (saffron) face challenges due to inconsistent flowering patterns and variations in yield. Flowering take place in a graded way with smaller corms being unable to produce flowers. Enhancing the productivity requires a comprehensive understanding of the underlying genetic mechanisms that govern this size based flowering initiation and commitment. Therefore, samples enriched with non-flowering and flowering apical buds from small (> 6g) and large (< 15g) corms were sequenced. Methods and Results Apical bud enriched samples from small and large corms were collected immediately after break of dormancy in month of July and performed RNA-sequencing on Illumina platform. De-novo transcriptome assembly and analysis using flowering committed buds from large corms at post-dormancy and their comparison with vegetative shoot primordia from small corms pointed out major role of Auxin and ABA hormonal regulation. Many genes with known dual response in flowering development and circadian rhythm like Flowering locus T and Cryptochrome 1 along with a transcript showing homology with small auxin upregulated RNA (SAUR) exhibited induced expression in flowering buds. Thorough prediction of Crocus sativus non-coding RNA repertoire has been carried out for the first time. Enolase was found to be acting as a major hub with protein-protein interaction analysis using Arabidopsis counterparts. Conclusion Transcripts belong to key pathways including phenylpropanoid biosynthesis, hormone signaling including and carbon metabolism were found significantly modulated. KEGG assessment and protein-protein interaction analysis conform the expression data. Findings unravel the genetic determinants driving the size-based flowering in Crocus sativus.