Analysis of the GTPase activity and active sites of the NG domains of FtsY and Ffh from Streptomyces coelicolor

MdIPT1, an adenylate isopentenyltransferase coding gene from Malus domestica, is involved in branching and flowering regulation

Flowering and shoot branching are significant agricultural traits for apple tree breeding. Cytokinin metabolism and signaling pathways play a crucial role in plant development. However, little is known about cytokinin biosynthetic molecular mechanism and function involved in apple flowering and branching. In this study, an adenylate isopentenyl transferase coding gene MdIPT1, homologous to AtIPT3/AtIPT5 in Arabidopsis thaliana, was identified. MdIPT1 was highly expressed in apple floral and axillary buds and was dramatically up-regulated during floral induction and axillary bud outgrowth. The promoter of MdIPT1 showed high activity in multiple tissues and responded to different hormone treatments. The MdIPT1-overexpressing Arabidopsis showed a multi-branching and early-flowering phenotype, with elevated endogenous cytokinin levels and altered expression of genes related to branching and flower formation. Overexpression of MdIPT1 confers the growth vigor of transgenic apple callus on a CKs-deficient medium. Our findings suggest that MdIPT1 is a positive regulator involved in branching and flowering. The data presented herein provide extensive research results on MdIPT1 and will contribute to molecular breeding for new apple varieties.

Analysis of the GTPase motif of FlhF in the control of the number and location of polar flagella in Vibrio alginolyticus

Vibrio alginolyticus normally has a single polar flagellum whose number and placement are regulated positively by FlhF. FlhF is a GTPase and homolog of a signal recognition particle (SRP) protein called Ffh and SRP receptor FtsY. FlhF is located at the cell pole and directs formation of the flagellum. To study the mechanism of FlhF localization, we introduced random mutations into flhF by means of hydroxylamine and isolated mutants that could not generate the flagellum at the cell pole. The novel mutations were only mapped to the GTPase motif of FlhF. The mutant FlhF proteins showed reduced polar localization as compared to the wild type and still could associate with the membrane. These results support the assumption that the GTPase motif of FlhF plays a critical role in the polar localization of this protein during formation of the flagellum.

The distinct anchoring mechanism of FtsY from different microbes

The SRP receptor FtsY, which is involved in targeting and translocating membrane protein, is generally composed of the N-terminal domain and the NG domain. Although FtsY was highly homologous in the composition of amino acids and functions among microbes, the different mechanism in the location of FtsYs from different bacteria such as S. coelicolor and E. coli were discovered in this study by laser scanning confocal microscope (LSCM) in vivo and molecular techniques in vitro. The results revealed that the N-terminal domain of S. coelicolor FtsY was indispensable for FtsY's anchoring membrane, and while the A domain of E. coli FtsY was dispensable. Moreover, the A domain of E. coli FtsY might promote itself to bind the membrane depending on the location images and Western blotting.