RNA processing and Arabidopsis flowering time control.

Plants control their flowering time in order to ensure that they reproduce under favourable conditions. The components involved in this complex process have been identified using a molecular genetic approach in Arabidopsis and classified into genetically separable pathways. The autonomous pathway controls the level of mRNA encoding a floral repressor, FLC, and comprises three RNA-binding proteins, FCA, FPA and FLK. FCA interacts with the 3'-end RNA-processing factor FY to autoregulate its own expression post-transcriptionally and to control FLC. Other components of the autonomous pathway, FVE and FLD, regulate FLC epigenetically. This combination of epigenetic and post-transcriptional control gives precision to the control of FLC expression and flowering time.

Co-ordination of pathogenicity island expression by the BipA GTPase in enteropathogenic Escherichia coli (EPEC).

BipA is a novel member of the ribosome binding GTPase superfamily and is widely distributed in bacteria and plants. We report here that it regulates -multiple cell surface- and virulence-associated -components in the enteropathogenic Escherichia coli (EPEC) strain E2348/69. The regulated components include bacterial flagella, the espC pathogenicity island and a type III secretion system specified by the locus of enterocyte effacement (LEE). BipA positively regulated the espC and LEE gene clusters through transcriptional control of the LEE-encoded regulator, Ler. Additionally, it affected the pattern of proteolysis of intimin, a key LEE-encoded adhesin specified by the LEE. BipA control of the LEE operated independently of the previously characterized regulators Per, integration host factor and H-NS. In contrast, it negatively regulated the flagella-mediated motility of EPEC and in a Ler-independent manner. Our results indicate that the BipA GTPase functions high up in diverse regulatory cascades to co-ordinate the expression of key pathogenicity islands and other virulence-associated factors in E. coli.