Identification of Differentially Expressed Genes Involved in the Molecular Mechanism of Pericarp Elongation and Differences in Sucrose and Starch Accumulation between Vegetable and Grain Pea (Pisum sativum L.)

Pea (Pisum sativum L.), as a major source of plant protein, is becoming one of the major cultivated crop species worldwide. In pea, the pericarp is an important determinant of the morphological characteristics and seed yield. To investigate the molecular mechanism of pericarp elongation as well as sucrose and starch accumulation in the pods of different pea cultivars, we performed transcriptomic analysis of the pericarp of two types of pea cultivar (vegetable pea and grain pea) using RNA-seq. A total of 239.44 Gb of clean sequence data were generated, and were aligned to the reference genome of Pisum sativum L. In the two samples, 1935 differentially expressed genes (DEGs) were identified. Among these DEGs, three antioxidant enzyme superoxide dismutase (SOD) were detected to have higher expression levels in the grain pea pericarps at the pod-elongating stages. Otherwise, five peroxidase (POD)-encoding genes were detected to have lower expression levels in the vegetative pericarps at the development stage of pea pod growth. Furthermore, genes related to starch and sucrose metabolism in the pea pod, such as SUS, INV, FBA, TPI, ADPase, SBE, SSS, and GBSS, were found to be differentially expressed. The RNA-seq data were validated through real-time quantitative RT-PCR of 13 randomly selected genes. Our findings provide the gene expression profile of, as well as differential expression information on, the two pea cultivars, which will lay the foundation for further studies on pod development and nutrition accumulation in the pea and provide valuable information for pea cultivar improvement.