Plant sulfolipid. II. Mutant study and phosphate deficiency

Abstract

Study with SQDG-deficient mutants showed that formation of the sulfonic acid precursor, UDP-sulfoquinovose, in higher plants is considered to be catalyzed by the orthologous plant proteins SQD1. The second required plant enzyme, SQD2, is highly similar to glycosyltransferases and it is proposed that this protein represents sulfolipid synthase. The results of recent works have shown that for the stable activity PS II needs the presence of SQDG and that it participates in PS II recovering through some mechanism dependent on light. Under phosphate-limiting conditions a decrease in the content of one acidic lipid (PG) was accompanied by an increase in the content of the other acidic lipid (SQDG), which resulted in the maintenance of a certain level of total acidic lipids of chloroplast membranes.