Red light regulates metabolic pathways of soybean hypocotyl elongation and thickening

Abstract

Plant stem growth and development are regulated by red light, which is an important environmental signal. Using proteomic and metabolomic approaches, differentially expressed proteins (DEPs) and differentially expressed metabolites (DEMs) in soybean hypocotyls were examined between soybean plants subjected to darkness and red light conditions, elucidating the pathways underlying the regulatory effects of red light on soybean hypocotyl growth. The results revealed that red light inhibits hypocotyl elongation and increases the hypocotyl diameter in soybeans. Red light inhibited hypocotyl elongation mainly by enhancing the firmness of the cell wall. First, red light promoted the expression of enzymes related to the conversion of serine and threonine to glycine, decreased the level of intracellular reactive oxygen species (ROS), and reduced the degradation of cell wall polysaccharides. Furthermore, by enhancing the expression of enzymes involved in the lignin monomer synthetic pathway, red light promoted the biosynthesis of lignin to strengthen the cell wall. Moreover, red light promoted hypocotyl thickening mainly by upregulating the expression of aminocyclopropanecarboxylate oxidase, thereby promoting the accumulation of ethylene precursors. This study provides a theoretical basis for using light to regulate soybean stem growth.