Galactolipids from Arabidopsis thaliana can replace the function of gluco lipids in Bacillus subtilis .

[摘要] Arabidopsis thaliana monogalactosyldiacylglycerolsynthase 1 (AtMGD1) and digalactosyldiacylglycerolsynthase 2 (AtDGD2) genes introduced into a Bacillus subtilis chromosome with disrupted galE, whichencodes UDP-glucose 4-epimerase, enabled themutant to produce monogalactosyldiacylglycerol.When galE mutant cells are cultivated in galactosecontaining medium they show abnormal morphology. This phenotype is correlated with a decreasein the amount of glucolipids. Nucleoids of the ugtPand galE mutants were stained by propidium iodide,which does not permeate intact cell membranes,whereas nucleoids of wild type and of a pssA mutantwe examined were not stained. Expression of theAtMGD1 gene in a ugtP galE double mutant restoredcell membrane integrity. Expression of galactolipidsynthase genes from a multi-copy plasmid,pDGHisN4, allowed higher production of galactolipids. Activation of the extracytoplasmic functionsigma factors SigM, SigV, and SigX, in the ugtPmutant was decreased by expression of AtMGD1,and SigX activity was strongly repressed when bothAtMGD1 and AtDGD2 genes were expressed in themutant. We conclude that the number of sugars thatbind to diacylglycerol - rather than the exact sugarspecies - is important for glycolipid function in B.subtilis.

[学科分类] 微生物学和免疫学

[关键词] Bacillus subtilis;glucolipid;galactolipid;Arabidopsis thaliana;ECF sigma factor;cell membrane integrity