Comparative secretome analysis of different smut fungi and identification of plant cell death-inducing secreted proteins from Tilletia horrida

Abstract

Background Tilletia 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. Results A 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. Conclusions Overall, 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 . Electronic supplementary material The online version of this article (10.1186/s12870-019-1924-6) contains supplementary material, which is available to authorized users.

Development of a loop-mediated isothermal amplification assay for the detection of Tilletia controversa based on genome comparison

“…Adding betaine was essential for successful amplification even though the target region was not GC-rich (52.2% GC). This finding is in conflict with a previous report that betaine had no effect on the amplification in non-GC-rich target regions 45 . We suggest that the formation of secondary structures rather than mere GC content may account for the effect of betaine.…”

Identification of the Novel Effector RsIA_NP8 in Rhizoctonia solani AG1 IA That Induces Cell Death and Triggers Defense Responses in Non-Host Plants

“…In this study, we selected 11 candidate effectors for functional assay; of these, only RsIA_NP8 triggered cell death in N. benthamiana. Further experiments showed that RsIA_NP8 was upregulated during the early stages of R. solani AG1 IA infection, similar to most other effectors, such as smut_2965 and smut_5844 in Tilletia horrida, which cause rice kernel smut (Wang et al, 2019). In addition, RsIA_NP8-triggered cell death in N. benthamiana depended on its SP.…”

“…It is interesting that the effector AGLIP1 in R. solani AG1 IA also requires its predicted SP to induce cell death (Li et al, 2019). This phenomenon has been observed in Ustilaginoidea virens and T. horrida (Fang et al, 2016;Wang et al, 2019). In U. virens, eight secreted proteins all required SPs to induce cell death in N. benthamiana and rice protoplasts (Fang et al, 2016).…”

“…In U. virens, eight secreted proteins all required SPs to induce cell death in N. benthamiana and rice protoplasts (Fang et al, 2016). In T. horrida, the full-length effector uan2 was able to trigger cell death in N. benthamiana; however, uan2 that lacked SPs was not (Wang et al, 2019).These results show that these proteins have characteristics in common and might function in the extracellular space (Morgan and Kamoun, 2007). A lack of SPs means that these proteins cannot be secreted into the extracellular matrix, where proteins are recognized by plasma membrane receptors (Nie et al, 2019).…”

Secretome Analysis of the Banana Fusarium Wilt Fungi Foc R1 and Foc TR4 Reveals a New Effector OASTL Required for Full Pathogenicity of Foc TR4 in Banana

“…Secretome profiling and prediction have been used to identify SPs of many pathogens, including Tilletia horrida [ 10 ], Fusarium proliferatum [ 11 ], Tilletia indica [ 12 , 13 ], rose black spot [ 4 ], Trichoderma virens [ 14 ], Arbuscular mycorrhizal [ 15 ], and Puccinia striiformis f. sp. tritici [ 16 ].…”