Overexpression of a Novel Biotrophy-Specific Colletotrichum truncatum Effector, CtNUDIX, in Hemibiotrophic Fungal Phytopathogens Causes Incompatibility with Their Host Plants

Abstract

The hemibiotrophic fungus Colletotrichum truncatum causes anthracnose disease on lentils and a few other grain legumes. It shows initial symptomless intracellular growth, where colonized host cells remain viable (biotrophy), and then switches to necrotrophic growth, killing the colonized host plant tissues. Here, we report a novel effector gene, CtNUDIX, from C. truncatum that is exclusively expressed during the late biotrophic phase (before the switch to necrotrophy) and elicits a hypersensitive response (HR)-like cell death in tobacco leaves transiently expressing the effector. CtNUDIX homologs, which contain a signal peptide and a Nudix hydrolase domain, may be unique to hemibiotrophic fungal and fungus-like plant pathogens. CtNUDIX lacking a signal peptide or a Nudix motif failed to induce cell death in tobacco. Expression of CtNUDIX:eGFP in tobacco suggested that the fusion protein might act on the host cell plasma membrane. Overexpression of CtNUDIX in C. truncatum and the rice blast pathogen, Magnaporthe oryzae, resulted in incompatibility with the hosts lentil and barley, respectively, by causing an HR-like response in infected host cells associated with the biotrophic invasive hyphae. These results suggest that C. truncatum and possibly M. oryzae elicit cell death to signal the transition from biotrophy to necrotrophy.

A comparative genomic analysis of putative pathogenicity genes in the host-specific sibling species Colletotrichum graminicola and Colletotrichum sublineola

“…protein kinases and protein phosphatases), and pathogenicity, e.g. proteins with LysM chitin-binding domains [84]; necrosis-inducing NPP domains [85]; NUDIX domains [86, 87]; and Common in Fungal Extracellular Membrane (CFEM) domains [88]. Seventeen percent of the C. sublineola NCPs, and 20% of the C. graminicola NCPs, matched entries in the PHI database.…”

Strategies for Wheat Stripe Rust Pathogenicity Identified by Transcriptome Sequencing

“…Interestingly, Bhadauria et. al [39] recently reported a novel effector gene from Colletotrichum truncatum ( CtNUDIX ) that is exclusively expressed during the late biotrophic phase and elicits the hypersensitive response in tobacco leaves, suggesting that this effector could be important for the transition from biotrophy to necrotrophy, or alternatively is recognised by the tobacco immune system. A secreted protein from Pst containing a NUDIX domain could potentially regulate redox homeostasis.…”

Achievements and Challenges in Legume Breeding for Pest and Disease Resistance

“…The hemi-biotrophic lentil anthracnose pathogen, Colletotrichum truncatum, expresses an effector gene, CtNUDIX, exclusively during the later biotrophic phase before switching to necrotophic phase, and elicits a hypersensitive response from the host plant (Bhadauria et al, 2011). Overexpression of CtNUDIX in the pathogen causes incompability with the host plant (Bhadauria et al, 2013).…”