Transcriptome mapping of unfertilized pea flowers under high temperature: insights into gene regulatory networks genomics resources

Heat stress is the most significant environmental constraint on pea production, and heat tolerance mechanisms are mediated through a variety of pathways. Pea (Pisum sativum L.) cultivar Arka Chaitra (AC) is considered a heat tolerant variety, whereas cultivar Matar Ageta (MA) is heat sensitive. Transcriptome profiling of two pea cultivars, AC and MA, was conducted under control and heat stress (HS) conditions to elucidate the molecular mechanisms and identify genes associated with heat tolerance. In this study, we initially reported the repertoire of morpho-physiological traits namely pod number (PNP), weight of pods (PW), seed number/pod (SNP) and weight of seed/pod (SW) during HS conditions in AC and MA. Subsequently, Pollen viability assay was performed to further examine the pollen behavior under HS. Morpho-physiological analysis revealed that cultivar AC exhibited greater number of pods and seeds, as well as higher pod and seed weights, compared to MA under HS. Furthermore, pollen viability in cultivar AC was reduced by 23 %, whereas in cultivar MA, it was reduced by 41 %, indicating that AC exhibits robust tolerance mechanisms under HS conditions. Based on these observations, we delve deeper to investigate the regulatory mechanisms by profiling the transcriptomes of cultivars AC and MA using RNA Sequencing (RNA-Seq) under HS. We selected a subset of genes, including heat shock transcription factors, and heat shock proteins involved in heat resilience, to validate the RNA-Seq expression patterns using quantitative RT-PCR, which revealed higher expression levels in AC compared to MA. Furthermore, gene ontology (GO) analysis of the identified DEGs revealed significant enrichment of GO terms associated with pollen and flower development, heat stress proteins, and plastid development in the tolerant variety, whereas, the susceptible variety was enriched with GO terms related to cell morphogenesis, cell growth, and cell wall biogenesis. These findings provide in-depth analysis of genes and pathways contributing to thermotolerance in pea cultivars AC and MA.