Abstract
Sporisorium reilianum f. sp. zeae (SRZ) is a biotrophic fungus causing head smut in maize. Maize infection with SRZ leads to very little cell death suggesting the presence of cell-death suppressinpg effectors. Several hundred effector proteins have been predicted based on genome annotation, genome comparison, and bioinformatic analysis. For only very few of these effectors, an involvement in virulence has been shown. In this work, we started to test a considerable subset of these predicted effector proteins for a possible function in suppressing cell death. We generated an expression library of 62 proteins of SRZ under the control of a strong constitutive plant promoter for delivery into plant cells via Agrobacterium tumefaciens-mediated transient transformation. Potential apoplastic effectors with high cysteine content were cloned with signal peptide while potential intracellular effectors were also cloned without signal peptide to ensure proper localization after expression in plant cells. After infiltration of Nicotiana benthamiana leaves, infiltration sites were evaluated for apparent signs of hypersensitive cell death in absence or presence of the elicitin INF1 of Phytophthora infestans. None of the tested candidates was able to induce cell death, and most were unable to suppress INF1-induced cell death. However, the screen revealed one predicted cytoplasmic effector (sr16441) of SRZ that was able to reliably suppress INF1-induced cell death when transiently expressed in N. benthamiana lacking its predicted secretion signal peptide. This way, we discovered a putative function for one new effector of SRZ.
Highlights
The phytopathogenic biotrophic basidiomycete Sporisorium reilianum f. sp. zeae (SRZ) is the causative agent of head smut disease of maize
To verify that none of the candidate effectors induces cell death, N. benthamiana leaves were first infiltrated with A. tumefaciens strains carrying each of the 62 constructs or the controls psojNIP (Qutob et al, 2002) or pGR106-INF1 (Huitema et al, 2005) that encode known cell death-inducing elicitins
Phenotypic evaluation of the infiltrated sites revealed that only the known elicitins NIP of P. sojae and INF1 of P. infestans but none of the 62 constructs led to cell death induction (Figure 2; Figure S1, see Supplemental Material available online)
Summary
The phytopathogenic biotrophic basidiomycete Sporisorium reilianum f. sp. zeae (SRZ) is the causative agent of head smut disease of maize. The disease can cause great damage and leads to complete harvest loss of affected individual plants. The disease is transmitted by soil-borne diploid teliospores. PCD-Suppressing Effector of S. reilianum meiosis, and generate haploid sporidia of different mating types (Hanna, 1929; Halisky, 1963; Martinez et al, 2002). Compatible haploid sporidia form conjugation hyphae that grow toward each other and fuse at their tips (Schirawski et al, 2005). The fungus grows as dikaryotic hyphae that penetrate and colonize the plant initially without causing severe symptoms (Martinez et al, 1999; Prom et al, 2011; Poloni and Schirawski, 2016). Symptoms become evident only at the flowering time when spore formation and phyllody occur in the inflorescences (Wilson and Frederiksen, 1970; Martinez et al, 1999; Ghareeb et al, 2011; Poloni and Schirawski, 2016)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
