Transcriptome analysis of ovules offers early developmental clues after fertilization in Cicer arietinum L.

Chickpea (Cicer arietinum L.) seeds are valued for their nutritional scores and limited information on the molecular mechanisms of chickpea fertilization and seed development is available. In the current work, comparative transcriptome analysis was performed on two different stages of chickpea ovules (pre- and post-fertilization) to identify key regulatory transcripts. Two-staged transcriptome sequencing was generated and over 208 million reads were mapped to quantify transcript abundance during fertilization events. Mapping to the reference genome showed that the majority (92.88%) of high-quality illumina reads were aligned to the chickpea genome. Reference-guided genome and transcriptome assembly yielded a total of 28,783 genes. Of these, 3399 genes were differentially expressed after the fertilization event. These involve up-regulated genes including LOC101500970, LOC101506539 and down-regulated genes LOC101493897, LOC101491695 and so on. Transcription factor families including UDP-glucuronyltransferase, NAC transcription factor, heat shock transcription factor, and auxin-responsive transcription factor were also found to be activated after fertilization. Activation of these genes and transcription factors results in the accumulation of carbohydrates and proteins by enhancing their trafficking and biosynthesis. Total 17 differentially expressed genes, were randomly selected for qRT-PCR for validation of transcriptome analysis and showed statistically significant correlations with the transcriptome data. Our findings provide insights into the regulatory mechanisms underlying changes in fertilized chickpea ovules. This work may come closer to a comprehensive understanding of the mechanisms that initiate developmental events in chickpea seeds. Total RNA was isolated pre- and post-fertilization ovules from chickpea using TRI-reagent. RNA-Seq library was generated on illumina platform.Sequencing of library was done on illumine Nextera 500 sequencing platform.