Leaping into the Unknown World of Sporisorium scitamineum Candidate Effectors

Abstract

Sporisorium scitamineum is a biotrophic fungus causing sugarcane smut disease. In this study, we set up a pipeline and used genomic and dual transcriptomic data previously obtained by our group to identify candidate effectors of S. scitamineum and their expression profiles in infected smut-resistant and susceptible sugarcane plants. The expression profile of different genes after infection in contrasting sugarcane genotypes assessed by RT-qPCR depended on the plant genotypes and disease progression. Three candidate effector genes expressed earlier only in resistant plants, four expressed in both genotypes, and three later in susceptible plants. Ten genes were cloned and transiently expressed in N. benthamiana leaves to determine their subcellular location, while four localized in more than one compartment. Two candidates, g3890 having a nucleoplasmic and mitochondrial location and g5159 targeting the plant cell wall, were selected to obtain their possible corresponding host targets using co-immunoprecipitation (CoIP) experiments and mass spectrometry. Various potential interactors were identified, including subunits of the protein phosphatase 2A and an endochitinase. We investigated the presence of orthologs in sugarcane and using transcriptome data present their expression profiles. Orthologs of sugarcane shared around 70% similarity. Identifying a set of putative fungal effectors and their plant targets provides a valuable resource for functional characterization of the molecular events leading to smut resistance in sugarcane plants and uncovers further opportunities for investigation.

Smuts to the Power of Three: Biotechnology, Biotrophy, and Basic Biology

“…Dual transcriptome data of resistant and susceptible sugarcane plants infected with Sporisorium scitamineum were used by N.S. Teixeira-Silva and coworkers to identify and investigate selected candidate effector proteins to determine their stage- and tissue-specific gene expression, subcellular localization, and possible plant interaction partners [ 8 ]. A specific fungal effector (UhAVR1) of Ustilago hordei that functions as an avirulence protein in barley plants carrying the resistance gene RUH1 was the object of study by A.P.…”

Identification of Gene Modules and Hub Genes Associated with Sporisorium scitamineum Infection Using Weighted Gene Co-Expression Network Analysis

“…A total of 68 effector candidates have been identified in the S. scitamineum genome [ 6 ]; while little is known about their roles in plants, only SsPele1 and SsPEP1 have been functionally characterized to date [ 7 ]. Additionally, the other five candidates, which contain characteristics of signal peptides, low molecular mass, and upregulation in planta , could affect programmed cell death (PCD) by using transient expression on Nicotiana benthamiana [ 8 , 9 ]. A lack of sufficient knowledge on effectors has prevented a complete understanding of the pathogenesis of sugarcane smut.…”

SsPEP1, an Effector with Essential Cellular Functions in Sugarcane Smut Fungus

“…In sugarcane, ROS accumulation and the expression of antioxidant enzymes differ between the primary meristem tissues of smut-resistant and smut-susceptible sugarcane genotypes following S. scitamineum infection [21], while an array of inferred fungal effectors has been found to be specifically upregulated in planta [22][23][24]. However, little is known about the contribution of these effectors to the virulence and maintenance of the fungus within the host plant [15].…”