NopD of Bradyrhizobium sp. XS1150 Possesses SUMO Protease Activity

Abstract

Effectors secreted by the type III protein secretion system (T3SS) of rhizobia are hostspecific determinants of the nodule symbiosis. Here, we have characterized NopD, a putative type III effector of Bradyrhizobium sp. XS1150. NopD was found to possess a functional N-terminal secretion signal sequence that could replace that of the NopL effector secreted by Sinorhizobium sp. NGR234. Recombinant NopD and the C-terminal domain of NopD alone can process small ubiquitin-related modifier (SUMO) proteins and cleave SUMO-conjugated proteins. Activity was abolished in a NopD variant with a cysteine-to-alanine substitution in the catalytic core (NopD-C 972 A). NopD recognizes specific plant SUMO proteins (AtSUMO1 and AtSUMO2 of Arabidopsis thaliana; GmSUMO of Glycine max; PvSUMO of Phaseolus vulgaris). Subcellular localization analysis with A. thaliana protoplasts showed that NopD accumulates in nuclear bodies. NopD, but not NopD-C 972 A, induces cell death when expressed in Nicotiana tabacum. Likewise, inoculation tests with constructed mutant strains of XS1150 indicated that nodulation of Tephrosia vogelii is negatively affected by the protease activity of NopD. In conclusion, our findings show that NopD is a symbiosis-related protein that can process specific SUMO proteins and desumoylate SUMO-conjugated proteins.

Rhizobia use a pathogenic-like effector to hijack leguminous nodulation signalling

“…Recently, NopD of Bradyrhizobium sp. XS1150 appears as characterized rhizobial SUMO protease facilitates a symbiotic efficiency 31 . ULP1 active-site function depends on the sequentially ordered catalytic-core triad His-Asp-Cys 32 .…”

“…The XopD effector was originally identified from Xcv., which causes spot disease on tomato and pepper plants, while the NopD restricts nodulation of Tephrosia vogelii by Bradyrhizobium sp. XS1150 31,56 . In the present study, we showed that the Bel2-5 positively regulates the activation of soybean nodulation signalling.…”

“…4), while it abolished the ability of X. campestris and Bradyrhizobium sp. XS1150 to elicit leaf necrosis in N. benthamiana 31,35 . The members of the ULP1 protease family were reported to modulate diverse functions of various molecular processes, including gene expression, chromatin remodelling, subcellular localization, and genome maintenance 57 .…”

Multiple Domains in the Rhizobial Type III Effector Bel2-5 Determine Symbiotic Efficiency With Soybean

“…Bel2-5 shares similarity with the rhizobial T3E NopD ( Xiang et al, 2020 ) and with XopD ( Noël et al, 2002 ), from the plant pathogen Xcv . ( Ratu et al, 2021 ).…”

“…ORS3257 ( Teulet et al, 2019 ), and NopD of Bradyrhizobium sp. XS1150 ( Xiang et al, 2020 ). However, whether their cellular/symbiotic activities depend on nuclear localization remains unknown.…”