Integrated Transcriptomic and Metabolomic Analyses of Seed-Filling Disorders in Soybeans Under Different Ecological Conditions

Abstract

Disorders in soybean seed-filling can lead to wrinkled seeds, affecting yield and quality. Previous studies have demonstrated that some soybean cultivars from Jiamusi, Heilongjiang Province (cold-temperate continental monsoon, ~3.5 °C mean annual temperature, ~530 mm precipitation) exhibit seed-filling disorders when cultivated in Shenyang, Liaoning Province (mid-temperate semi-humid continental monsoon, ~8.3 °C, ~610 mm). However, the causes and regulatory mechanisms remain unclear. In this study, Henong 76 (a soybean cultivar with seeds less prone to wrinkling) and Heihe 43 (a soybean cultivar with seeds prone to wrinkling) were used as experimental materials. They were sown simultaneously in Jiamusi and Shenyang, respectively, to explore the causes of seed-filling disorders in Heihe 43. The results indicated that there were significant differences in the contents of soluble sugars and starch, as well as in the activities of sucrose synthase and invertase, between the seeds of Henong 76 and Heihe 43 grown in Shenyang. However, no significant differences were found between them in Jiamusi. Transcriptomic and metabolomic analyses suggested that genes related to controlling starch hydrolysis (isoamylase, α-amylase, and glycogen phosphorylase) and sucrose synthesis and decomposition (sucrose synthase, invertase, glucose-6-phosphate isomerase, and phosphoglucomutase) in Heihe 43 were upregulated in Shenyang. In contrast, genes regulating plant hormone signal transduction (auxin, gibberellin, abscisic acid, and cytokinin) were generally downregulated. These changes led to differences in metabolites, resulting in the occurrence of seed-filling disorders. Furthermore, we analyzed the climatic conditions of the two cultivars during the soybean seed-filling period. The results indicated that high temperature might be the primary meteorological factor contributing to the occurrence of seed-filling disorders. All results indicated that the insufficient accumulation of sugars in seeds due to exposure to high temperatures during the seed-filling period is the primary cause of the prone-to-wrinkling phenomenon of the Heihe 43 cultivar under the ecological conditions of Shenyang.