Septal membrane localization by C-terminal amphipathic α-helices of MinD in Bacillus subtilis mutant cells lacking MinJ or DivIVA

Identification and expression analysis of MinD gene involved in plastid division in cassava

Cassava is a tropical crop known for its starchy root and excellent properties. Considering that starch biosynthesis in the amyloplast is affected by its division, it appears conceivable that the regulation of plastid division plays an important role in starch accumulation. As a member of the Min system genes, MinD participated in the spatial regulation of the position of the plastid division site.In our studies, sequence analysis and phylogenetic analysis showed that MeMinD has been highly conserved during the evolutionary process. Subcellular localisation indicated that MeMinD carries a chloroplast transit peptide and was localised in the chloroplast. Overexpression of MeMinD resulted in division site misplacement and filamentous formation in E. coli, indicating that MeMinD protein was functional across species. MeMinD exhibited different spatial and temporal expression patterns which was highly expressed in the source compared to that in the sink organ.

Biological functions of glucolipids in Bacillus subtilis

Glyceroglycolipids are very important in Gram-positive bacteria and cyanobacteria. In Bacillus subtilis, a model organism for the Gram-positive bacteria, the ugtP mutant, which lacks glyceroglucolipids, shows abnormal morphology. Lack of glucolipids has many consequences: abnormal localization of the cytoskeletal protein MreB and activation of some extracytoplasmic function (ECF) sigma factors (σ^M, σ^V and σ^X) in the log phase are two examples. Conversely, the expression of monoglucosyldiacylglycerol (MGlcDG) by 1,2-diacylglycerol 3-glucosyltransferase from Acholeplasma laidlawii (alMGS) almost completely suppresses the ugtP disruptant phenotype. Activation of ECF sigmas in the ugtP mutant is decreased by alMGS expression, and is suppressed to low levels by MgSO₄ addition. When alMGS and alDGS (A. laidlawii 1,2-diacylglycerol-3-glucose (1-2)-glucosyltransferase producing diglucosyldiacylglycerol (DGlcDG)) are simultaneously expressed, σ^X activation is repressed to wild type level. These observations suggest that MGlcDG molecules are required for maintenance of B. subtilis cell shape and regulation of ECF sigmas, and that DGlcDG regulates σ^X activity. The activation of ECF sigmas is not accompanied by proteolysis of anti-σ. Thus, glyceroglucolipids may have the specific role of helping membrane proteins function by acting in the manner of chaperones.