Secreted Glycosyltransferase RsIA_GT of Rhizoctonia solani AG-1 IA Inhibits Defense Responses in Nicotiana benthamiana

Abstract

Anastomosis group AG-1 IA of Rhizoctonia solani Khün has a wide host range and threatens crop production. Various glycosyltransferases secreted by phytopathogenic fungi play an essential role in pathogenicity. Previously, we identified a glycosyltransferase RsIA_GT (AG11A_09161) as a secreted protein-encoding gene of R. solani AG-1 IA, whose expression levels increased during infection in rice. In this study, we further characterized the virulence function of RsIA_GT. It is conserved not only in Basidiomycota, including multiple anastomosis groups of R. solani, but also in other primary fungal taxonomic categories. RsIA_GT possesses a signal peptide (SP) for protein secretion, and its functionality was proven using yeast and Nicotiana benthamiana. The SP-truncated form of RsIA_GT (RsIA_GT(ΔS)) expressed in Escherichia coli-induced lesion-like phenotype in rice leaves when applied to punched leaves. However, Agrobacterium-mediated transient expressions of both the full-length RsIA_GT and RsIA_GT(ΔS) did not induce cell death in N. benthamiana leaves. Instead, only RsIA_GT(ΔS) suppressed the cell death induced by two reference cell death factors BAX and INF1 in N.benthamiana. RsIA_GT(ΔS)R154A D168A D170A, a mutant RsIA_GT(ΔS) for the glycosyltransferase catalytic domain, still suppressed the BAX- or INF1-induced cell death, suggesting that the cell death suppression activity of RsIA_GT(ΔS) would be independent from its enzymatic activity. RsIA_GT(ΔS) also suppressed the H2O2 production and callose deposition and showed an effect on the induction of defense genes associated with the expression of BAX and INF1. The transient expression of RsIA_GT(ΔS) in N. benthamiana enhanced the lesion area caused by R. solani AG-1 IA. The secreted glycosyltransferase, RsIA_GT, of R. solani AG-1 IA is likely to have a dual role in virulence inside and outside of host cells.

Mitochondrial‐targeting effector RsIA_CtaG/Cox11 in Rhizoctonia solani AG‐1 IA has two functions: plant immunity suppression and cell death induction mediated by a rice cytochrome c oxidase subunit

“…In general, effectors share the common property of inducing or inhibiting cell death in plants (Bos et al., 2006; Chen et al., 2021; Sharpee et al., 2017; Wei et al., 2020; Zhang et al., 2022). We have previously reported that the purified recombinant RsIA_CtaG/Cox11 could induce disease‐like symptoms when infiltrated into rice leaves (Zheng et al., 2013).…”

“…Since the beginning of the draft genome analysis of R. solani AG‐1 IA, we have characterized several candidate effectors (Niu et al., 2023; Wei et al., 2020; Xia et al., 2017; Zhang et al., 2022; Zheng et al., 2013). RsIA_CtaG/Cox11 is one of the first effector candidates to be experimentally verified, but our previous results were limited.…”

“…(2020) reported that the protease inhibitor RsRlpA exhibits cell death suppressive activity. RsIA_GT shows cell death suppressive activity and induces H 2 O 2 accumulation and callose deposition (Zhang et al., 2022). To the best of our knowledge, RsIA_CtaG/Cox11 is the third Rhizoctonia effector with cell death suppressive activity.…”

Comparative pangenomic insights into the distinct evolution of virulence factors among grapevine trunk pathogens

“…The expanded and contracted families of this species also showed enrichment in the transporters 2.A.1 (Major Facilitator Superfamily, P = 1.87e-58, Fisher’s Exact Test), which, among other roles, have been involved in resistance to oxidative stress and fungicides in some pathogenic fungi (49, 50). Lastly, the expanded and contracted families in N. parvum are enriched in glycosyltransferases (GT1_153) ( P = 1.08e-16, Fisher’s Exact Test, Supplementary figure 9), which have been associated with virulence in some pathogenic fungi (51, 52).…”

The function of the phytoplasma effector SWP12 depends on the properties of two key amino acids

“…As an HR-like stimulator, Bax is important for the study of effector immune function ( 52 ). When used as an activator, Bax is an important factor for screening whether the pathogen effector inhibits the immune response ( 40 , 52 , 53 ). Therefore, Bax can be used as a convenient elicitor to screen the functional domains of immunosuppressive effectors of phytoplasmas that cannot be cultured in vitro .…”