Chlorophyll a/b-binding Overexpression 2 regulates nitric oxide signaling in Arabidopsis response to sulfur deficiency

Abstract

Several studies have been conducted on plant responses to nutrient stressors; however, the mechanism underlying low-sulfur (LS) stress responses is still unclear. Here, we elucidated the function of COE2 in Arabidopsis response to sulfur deficiency using a series of phenotypic, physiological, biochemical, and molecular studies of the loss-of-function of COE2 (coe2 mutant). Under low sulfur conditions, WT seedlings had considerably longer roots than the coe2 seedlings. Although the chlorophyll fluorescence of coe2 and WT was lower under low sulfur, the reduction was more pronounced in the WT seedlings, indicating WT sensitivity to LS stress. Next, RNA-sequencing analysis was performed to investigate the roles of the COE2 in Arabidopsis response to sulfur deficiency at the molecular level. The coe2 and WT leaves responded to the induction of genes related to jasmonic acid, abscisic acid, and water deprivation, which are all crucial for leaf growth and defense. WT roots had more upregulated genes than the coe2 roots; thus, activation of these genes is tightly linked to WT and coe2 root responses to LS stress. We further evaluated the involvement of AtPSBO1 (a photosynthetic-inducible gene) in coe2 growth regulation under LS conditions. Compared with the coe2 seedlings, plants expressing 35S::PSBO1 exhibit increased sensitivity to sulfur deficiency in the leaves and roots, suggesting COE2 functions in chloroplast and root development under LS conditions. This study highlights the crucial roles of COE2 in root-shoot coordination in response to sulfur deficiency.