The Small GTPase ROP10 of Medicago truncatula Is Required for Both Tip Growth of Root Hairs and Nod Factor-Induced Root Hair Deformation

Abstract

Rhizobia preferentially enter legume root hairs via infection threads, after which root hairs undergo tip swelling, branching, and curling. However, the mechanisms underlying such root hair deformation are poorly understood. Here, we showed that a type II small GTPase, ROP10, of Medicago truncatula is localized at the plasma membrane (PM) of root hair tips to regulate root hair tip growth. Overexpression of ROP10 and a constitutively active mutant (ROP10CA) generated depolarized growth of root hairs, whereas a dominant negative mutant (ROP10DN) inhibited root hair elongation. Inoculated with Sinorhizobium meliloti, the depolarized swollen and ballooning root hairs exhibited extensive root hair deformation and aberrant infection symptoms. Upon treatment with rhizobia-secreted nodulation factors (NFs), ROP10 was transiently upregulated in root hairs, and ROP10 fused to green fluorescent protein was ectopically localized at the PM of NF-induced outgrowths and curls around rhizobia. ROP10 interacted with the kinase domain of the NF receptor NFP in a GTP-dependent manner. Moreover, NF-induced expression of the early nodulin gene ENOD11 was enhanced by the overexpression of ROP10 and ROP10CA. These data suggest that NFs spatiotemporally regulate ROP10 localization and activity at the PM of root hair tips and that interactions between ROP10 and NF receptors are required for root hair deformation and continuous curling during rhizobial infection.

Medicago falcata MfSTMIR, an E3 ligase of endoplasmic reticulum‐associated degradation, is involved in salt stress response

“…To isolate the soluble cytoplasm and insoluble membrane, the 35S: MfSTMIR ‐FLAG fusion protein was transiently expressed in N. benthamiana and extracted as described previously (Lei et al ., ). The protein concentrations from the soluble or insoluble fractions were measured using the Coomassie (Bradford) protein assay kit and were adjusted to equal concentrations.…”

Bradyrhizobium diazoefficiens USDA 110-Glycine max interactome provides candidate proteins associated with symbiosis

“…They can coordinate the development of epidermal and cortical cells to ensure rhizobial invasion and nodule initiation [7, 72]. Previous studies have confirmed the involvement of many nod factors in the signal transduction processes such as G-protein coupled receptor signaling pathways [73, 74], small GTPase mediated signal transduction [75, 76], calmodulin [77], Soluble N-Ethylmaleimide Sensitive Factor Attachment Protein Receptor (SNARE) proteins [58, 78] and the MAPK (Mitogen-activated protein kinase) cascade [79]. In the present study, 34 G-proteins, 18 small GTPase, 32 calmodulin and 18 SNARE proteins were present in the predicted PPIs and directly interacted with bacteria (Tables 1 and S8).…”

ROP GTPases Structure-Function and Signaling Pathways

“…In Medicago trancatula and Lotus japonicus ROPs, MtROP10 and LjROP6 interact with the RLKs MtNFP and LjNFR5 in the membrane, respectively, and are required for rhizobium-induced nodule formation and for tip growth (Ke et al, 2012(Ke et al, , 2016Lei et al, 2015;Rivero et al, 2017). It is not known yet whether ROPGEFs colocalize with the respective ROPs and RLKs.…”