Cross-kingdom small RNA communication between plants and fungal phytopathogens-recent updates and prospects for future agriculture

Abstract

Small RNAs (sRNAs) are short non-coding regulatory RNA sequences that silence the complementary expressive transcripts through an endogenous RNA mediated interference mechanism (RNAi). These sRNAs typically move through plasmodesmata and phloem in plants to support disease resistance, and also through septal pores and vesicles in fungi to act as effector of pathogenicity. Notably, recent reports have shown the occurrence of a bidirectional trafficking of these sRNAs between the host plants and the attacking fungal phytopathogen which have significant implication in the nature of the infection. While the trans-species sRNAs from the pathogen can silence the host mRNAs and inhibit the host immunity genes, the sRNA modules from the host plants can silence the mRNA in the pathogen by impeding the expression of the pathogenicity-related genes. In the present review, we discuss the current state of sRNA trafficking between the plant and the pathogen with special emphasis on the mechanism of cross-kingdom communication which could contribute to the development of pathogen and pest control in future agriculture.

Keywords: Fungal sRNA; RNA interference; extracellular vesicles; plant immunity; plant mirnas.

Figure 1.

Cross kingdom RNA interference in plant–fungus interactions. Plant derived small RNAs (sRnas) can be packaged by Golgi and is efficiently absorbed by fungal cell which inhibits germination of spore and development of mycelia by cleaving the pathogenicity target gene. Fungal pathogen also deploy group of sRnas to plant to silences the host resistance gene. Plant use extracellular vesicle to transport small RNA into the fungal cell for inhibiting virulence related genes. The mechanism of transport for fungal sRnas is unclear.

Figure 2.

Strategies to prevent fungal infection by Host induced Gene Silencing (HIGS) and Spray Induced Gene Silencing (SIGS) A) HIGS pathway: Transgenic plant after producing dsRNA, undergo cleavage by using plant Dicer like (DCL), converting to small interfering RNA (siRNA). Both dsRNA and siRNA move to pathogen cell through plasma membrane silences virulence mRNA (target gene). B) SIGS Pathway: After construction of dsRNA/siRNA, are sprayed onto topical part of plant, which are directly taken by plant cell, by using plant Dicer like protein (DCL), dsRNA converted to siRNA. Both dsRNA and siRNA move towards fungal cell by plasma membrane and target fungal virulence mRNA.