Abstract
BackgroundTilletia horrida is a basidiomycete fungus that causes rice kernel smut, one of the most important rice diseases in hybrid rice growing areas worldwide. However, little is known about its mechanisms of pathogenicity. We previously reported the genome of T. horrida, and 597 genes that encoded secreted proteins were annotated. Among these were some important effector genes related to pathogenicity.ResultsA secretome analysis suggested that five Tilletia fungi shared more gene families than were found in other smuts, and there was high conservation between them. Furthermore, we screened 597 secreted proteins from the T. horrida genome, some of which induced expression in host-pathogen interaction processes. Through transient expression, we demonstrated that two putative effectors could induce necrosis phenotypes in Nicotiana benthamiana. These two encoded genes were up-regulated during early infection, and the encoded proteins were confirmed to be secreted using a yeast secretion system. For the putative effector gene smut_5844, a signal peptide was required to induce non-host cell death, whereas ribonuclease catalytic active sites were required for smut_2965. Moreover, both putative effectors could induce an immune response in N. benthamiana leaves. Interestingly, one of the identified potential host interactors of smut_5844 was laccase-10 protein (OsLAC10), which has been predicted to be involved in plant lignification and iron metabolism.ConclusionsOverall, this study identified two secreted proteins in T. horrida that induce cell death or are involved in defense machinery in non-host plants. This research provides a useful foundation for understanding the interaction between rice and T. horrida.
Highlights
Tilletia horrida is a basidiomycete fungus that causes rice kernel smut, one of the most important rice diseases in hybrid rice growing areas worldwide
The results showed that T. horrida, Tilletia caries, Tilletia controversa, Tilletia indica, and Tilletia walker possessed more secreted proteins than Sporisorium scitamineum, Sporisorium reilianum, U. hordei, and U. maydis (Table 1; Additional file 1: Table S1)
51 gene families were shared among T. horrida and eight other smut fungi; 64 gene families were shared among T. horrida and S. scitamineum, S. reilianum, U. horde, and U. maydis; 177 gene families were shared among five Tilletia fungi; and 230 gene families appeared to be unique to T. horrida (Fig. 1a, b, c)
Summary
Tilletia horrida is a basidiomycete fungus that causes rice kernel smut, one of the most important rice diseases in hybrid rice growing areas worldwide. We previously reported the genome of T. horrida, and 597 genes that encoded secreted proteins were annotated. Among these were some important effector genes related to pathogenicity. The basidiomycete Tilletia horrida is a biotrophic fungal pathogen that causes rice kernel smut (RKS), a disease that is distributed throughout hybrid rice growing areas worldwide [1, 2]. The pathogens can secrete many effectors into host cells that suppress plant immune responses; these may be localized to different cellular compartments where they may assume diverse cellular
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