“…In yet other studies, the role of HRXXN kinases in cellular processes other than the GSR has been demonstrated (44)(45)(46), although, at the same time, their involvement in the GSR has not been assessed, and thus cannot be excluded at this time. For example, in Rhizobium leguminosarum, the orphan HRXXN kinase R-LOV-HK (pLR110320) regulates light-dependent cell attachment, exopolysaccharide production, and nodulation, but the response regulator presumably mediating this response was not identified and the involvement of PhyR in these phenotypes has not been studied (44). In another example, the HRXXN kinase SMa0113 of S. meliloti was shown to regulate both succinatemediated catabolite repression (SMCR) and polyhydroxybutyrate (PHB) production, but its cognate SDRR, SMa0114, seems dispensable for SMCR regulation and plays a noncanonical role in PHB production.…”