Sulfoquinovosyldiacylglycerol has an Essential Role in Thermosynechococcus elongatus BP-1 Under Phosphate-Deficient Conditions

In this study, we inactivated the sqdB gene, encoding a UDP-sulfoquinovose synthase and involved in SQDG biosynthesis, in Thermosynechococcus elongatus BP-1. In wild-type cells, PG accounted for only approximately 3.5 mol% of total membrane lipids, but its content was substantially increased along with complete loss of SQDG in the sqdB mutant. Under phosphate (Pi)-sufficient conditions, the growth rate and PSII activity were slightly lower in sqdB than in wild-type cells. In addition, the formation of PSI trimers and PSII dimers and energy transfer in phycobilisomes were perturbed in the mutant. Under Pi-deficient conditions, the growth of sqdB cells was severely impaired, with a decrease in PSII activity. PG supplementation could partially rescue the defective growth and PSII activity of Pi-deficient sqdB cells but fully recovered the impaired growth of the pgsA mutant of T. elongatus, which is deficient in PG biosynthesis. These data suggest that SQDG has a specific role in the growth and photosynthesis of T. elongatus, which cannot be complemented by PG, particularly under Pi-deficient conditions.
Source: Plant and Cell Physiology - Category: Cytology Authors: Tags: Regular Papers Source Type: research