Rare lost allele that boosts soybean seed protein identified

A research team led by Professor Hou

Their findings were published in the Proceedings of the National Academy of Sciences on October 30.

The domestication of wild plants into crops represents a major advance in human history, but key beneficial traits are often lost in the process. Soy is a good example. Modern soybean cultivars have lower seed protein content (30-40%) than their wild ancestors, wild soybean (Glycine Soya), which typically contains 50-60% protein. Since soy (Glycine max [L.] Merr.) are the main source of plant protein for livestock feed and human nutrition, increasing the protein content of seeds is a key objective of agricultural research.

As part of this effort, the Chinese researchers wanted to understand which genes are responsible for high seed protein in wild soybean ancestors, a question that had not yet been fully answered. To do this, the researchers conducted a GWAS on the protein content of seeds from a natural soybean population. Through this work, they identified a rare natural allele of Protein Contributor 08 (PC08) in wild soybean, which enhances seed protein levels but was lost during the domestication of soybean into modern crops.

Functional analysis further clarified the role of PC08 in storage protein accumulation. The natural variation of PC08 found in wild soybean includes a short insertion in its promoter region (PC08^Ins), which boosts gene expression. This increased expression increases abscisic acid (ABA) levels in seeds and ultimately promotes the accumulation of storage proteins.

Population genetic analysis confirmed that the protein-rich PC08 haplotype^Ins is exclusive to wild soybeans and was not retained during domestication. To validate its potential, researchers introgressed PC08^Ins into a cultivated soybean variety called Hei Nong 35. The resulting backcrossed soybean seeds showed a significant increase in seed protein content, demonstrating that PC08 has potential for molecular breeding efforts aimed at improving soybean seed protein content.