Genetic Mapping Combined with a Transcriptome Analysis to Screen for Candidate Genes Responsive to Abscisic Acid Treatment in Brassica napus Embryos During Seed Germination

Brassica napus embryos contain precursor tissues for the leaves, stem, and root, as well as the cotyledons, and these precursor tissues play key roles in seed germination, seedling survival, and subsequent seedling growth. Abscisic acid (ABA) plays a prominent role in the inhibition of seed germination. The underlying molecular mechanisms of the embryo responses to ABA stress followed by inhibited seed germination have not been reported in B. napus to date. In this study, we conducted quantitative trait locus (QTL) analysis of B. napus seed in response to ABA stress using 170 recombinant inbred lines. Furthermore, we performed transcriptome sequencing (RNA-seq) analyses by using B. napus ZS11 embryos under control (cytokinine [CK]) and 10 mg/L (10A), 20 mg/L (20A), and 30 mg/L (30A) ABA treatment conditions. In total, 10 QTLs were screened for explaining 2.70-6.73% of the phenotypic variation under ABA stress. In addition, 1495, 3332, and 3868 differentially expressed genes (DEGs) were identified in the CK vs 10A, CK vs 20A, and CK vs 30A comparisons, respectively. Gene Ontology (GO) enrichment analysis indicated that DEG functions are mainly related to response to stimuli, response to oxygen-containing compounds, response to lipids, and the transport and seed dormancy processes. These DEGs mainly participated in the response to plant hormone signal transduction, starch and sucrose metabolism, cutin, suberine, and wax biosynthesis, and phenylpropanoid biosynthesis processes pathways. Our results provide a foundation for further explorations of the molecular regulatory mechanisms of B. napus embryos in response to abiotic stress during the seed germination stage.