A seed germination transcriptomic study contrasting two soybean genotypes that differ in terms of their tolerance to the deleterious impacts of elevated temperatures during seed fill.

Objective: Soybean seed development is negatively impacted by elevated temperatures during seed fill, which can decrease seed quality and economic value. Prior germplasm screens identified an exotic landrace able to maintain ~ 95% seed germination under stress conditions that reduce germination dramatically (> 50%) for typical soybean seeds. Seed transcriptomic analysis was performed for two soybean lines (a heat-tolerant landrace and a typical high-yielding adapted line) for dry, mature seed, 6-h imbibed seed and germinated seed. Seeds were produced in two environments: a typical Midwestern field and a heat stressed field located in the Midsouth soybean production region.

Results: Transcriptomic analysis revealed 23-30K expressed genes in each seed tissue sample, and differentially expressed genes (DEGs) with ≥ twofold gene expression differences (at q-value < 0.05) comprised ~ 5-44% of expressed genes. Gene ontology (GO) enrichment analysis on DEGs revealed enrichment in heat-tolerant seeds for genes annotated for general and temperature-specific stress, as well as protein-refolding. DEGs were also clustered in modules using weighted co-expressed gene network analysis, which were examined for enrichment of GO biological process terms. Collectively, our results provide new and valuable insights into this unique form of genetic abiotic stress tolerance and to soybean seed physiological responses to elevated temperatures.