Utilization of a chloroplast membrane sulfolipid as a major internal sulfur source for protein synthesis in the early phase of sulfur starvation in Chlamydomonas reinhardtii

Abstract 

Information is limited on sulfur (S)-sources inside plant cells for synthesis of the proteins for acclimation to S-starvation. We found that a green alga, Chlamydomonas reinhardtii, when transferred to S-starved conditions, degrades 85% of a chloroplast membrane lipid, sulfoquinovosyl diacylglycerol (SQDG), to redistribute its S to a large part of protein fraction as early as by 6h. Furthermore, the degradation of SQDG preceded that of proteins such as ribulose bisphosphate carboxylase/oxygenase, the candidates of internal S-sources. SQDG was thus demonstrated to yield a major internal S-source for protein synthesis during the early phase of acclimation process to S-starvation.

Abbreviations: Chl, chlorophyll, Rubisco, ribulose bisphosphate carboxylase/oxygenase, S, sulfur, SQDG, sulfoquinovosyl diacylglycerol, TAP, tris/acetate/phosphate, TCA, trichloroacetic acid

Keywords: Sulfolipid, Sulfoquinovosyl diacylglycerol, Sulfur source, Chloroplast membranes, Sulfur starvation, Chlamydomonas reinhardtii