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

Abstract

Mesorhizobium loti MAFF303099 has a functional type III secretion system (T3SS) that is involved in the determination of nodulation competitiveness on Lotus. The M. loti T3SS cluster contains gene y4yS (mlr8765) that codes for a protein of unknown function (Y4yS). A mutation in the y4yS gene favors the M. loti symbiotic competitive ability on Lotus tenuis 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. In silico 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 y4yS-encoded protein is required for the formation of the M. loti T3SS secretin (RhcC2) complex. Remarkably, analysis of RhcC2 in the wild-type and M. loti y4yS mutant strains indicated that the absence of Y4yS affects negatively the accumulation of normal levels of RhcC2 in the membrane.

Transcriptional responses of soybean roots to colonization with the root endophytic fungus Piriformospora indica reveals altered phenylpropanoid and secondary metabolism

“…Recent work also suggests that effectors produced by P . indica mediate suppression of innate immunity to allow for colonization 129 .…”

Massive rhizobial genomic variations associated with partner quality inLotus–Mesorhizobiumsymbiosis

“…586 japonicus and Meshorhizobium because dysfunctional mutants of such genes in M. 587 japonicum did not show phenotypic changes in terms of nodule-forming ability for L. 588 japonicus B129 (Okazaki et al 2010), although their effects have been detected in other 589Lotus species(Okazaki et al 2010;Mercante et al 2015). 590We speculate that the contrasting findings between our study and previous ones 591might have arisen in part from differences in sampling schemes and in the unique 592 history of L. japonicus-associated symbionts.…”

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

“…The work of Mercante et al ( 2015 ) nicely complements these findings by showing that a predicted lipoprotein ( y4yS ) of the Mesorhizobium loti Rhc -T3SS could act as a potential pilotin by influencing the level of RhcC2 protein present in bacterial membranes, while sharing common characteristics (tetatricopeptide repeats, TPRs) of the Tad system pilotins.…”