Hidden players in plant response to sulfur deficit and beyond: insights into the function of the proteins Sulfur Deficiency Induced and Response to Low Sulfur

Sulfur is an essential macronutrient for plants, playing a central role in diverse metabolic processes. Under sulfur-deficient conditions, plants undergo extensive transcriptional reprogramming, which includes the induction of numerous genes encoding proteins of largely unknown function. Among these, two protein families have been studied more intensively: SDI (Sulfur Deficiency Induced) and LSU (Response to Low Sulfur). This review summarizes current experimental evidence on their involvement in sulfur assimilation, stress responses, and overall plant adaptation to sulfur scarcity. Special emphasis is placed on the LSU family, where recent evidence suggests that the function of these proteins extends beyond sulfur starvation responses, pointing to broader roles in plant growth, development, and resilience to diverse stresses.