AUTHOR=Mercante Virginia , Duarte Cecilia M. , Sánchez Cintia M. , Zalguizuri Andrés , Caetano-Anollés Gustavo , Lepek Viviana C. 

TITLE=The absence of protein Y4yS affects negatively the abundance of T3SS Mesorhizobium loti secretin, RhcC2, in bacterial membranes

JOURNAL=Frontiers in Plant Science

VOLUME=6

YEAR=2015

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2015.00012

DOI=10.3389/fpls.2015.00012

ISSN=1664-462X

ABSTRACT=<p><italic>Mesorhizobium loti</italic> MAFF303099 has a functional type III secretion system (T3SS) that is involved in the determination of nodulation competitiveness on Lotus. The <italic>M. loti</italic> T3SS cluster contains gene <italic>y4yS</italic> (<italic>mlr8765</italic>) that codes for a protein of unknown function (Y4yS). A mutation in the <italic>y4yS</italic> gene favors the <italic>M. loti</italic> symbiotic competitive ability on <italic>Lotus tenuis</italic> cv. Esmeralda and affects negatively the secretion of proteins through T3SS. Here we localize Y4yS in the bacterial membrane using a translational reporter peptide fusion. <italic>In silico</italic> analysis indicated that this protein presents a tetratricopeptide repeat (TPR) domain, a signal peptide and a canonical lipobox LGCC in the N-terminal sequence. These features that are shared with proteins required for the formation of the secretin complex in type IV secretion systems and in the Tad system, together with its localization, suggest that the <italic>y4yS</italic>-encoded protein is required for the formation of the <italic>M</italic>. <italic>loti</italic> T3SS secretin (RhcC2) complex. Remarkably, analysis of RhcC2 in the wild-type and <italic>M. loti y4yS</italic> mutant strains indicated that the absence of Y4yS affects negatively the accumulation of normal levels of RhcC2 in the membrane.</p>