Multiomics Analyses Reveal the Dual Role of Flavonoids in Pigmentation and Abiotic Stress Tolerance of Soybean Seeds

The
color of the seed coat has great diversity and is regarded
as a biomarker of metabolic variations. Here we isolated a soybean
variant (BLK) from a population of recombinant inbred lines with a
black seed coat, while its sibling plants have yellow seed coats (YL).
The BLK and YL plants showed no obvious differences in vegetative
growth and seed weight. However, the BLK seeds had higher anthocyanins
and flavonoids level and showed tolerance to various abiotic stresses
including herbicide, oxidation, salt, and alkalinity during germination.
Integrated metabolomic and transcriptomic analyses revealed that the
upregulation of biosynthetic genes probably contributed to the overaccumulation
of flavonoids in BLK seeds. The transient expression of those biosynthetic
genes in soybean root hairs increased the levels of total flavonoids
or anthocyanins. Our study revealed the molecular basis of flavonoid
accumulation in soybean seeds, leveraging genetic engineering for
both nutritious and stress-tolerant soybean germplasm.