Abstract
We previously found that sulfoquinovosyl diacylglycerol (SQDG), the major sulfolipid in the chloroplasts, was degraded under the sulfur-starved condition in Chlamydomonas reinhardtii. We here report the novel role of SQDG as sulfur-source for acclimation to sulfur-starvation. After [35S]-labeled cells of C. reinhardtii were shifted to the sulfur-starved condition, the radioactivity of SQDG, which had occupied 11% of total cellular-sulfur, was decreased to 2% in 6h. On the other hand, sulfur released from SQDG was incorporated into proteins. Since an SQDG-lacking mutant of C. reinhardtii, as compared with the wild type, showed defects in synthesis of chlorophyll-protein complexes, induction of sulfate transport activity, and growth during sulfur-starvation, the re-distribution of sulfur from SQDG proved critical for acclimation to sulfur-starvation.
