UvAtg8-Mediated Autophagy Regulates Fungal Growth, Stress Responses, Conidiation, and Pathogenesis in Ustilaginoidea virens

Abstract

Background: Ustilaginoidea virens has become one of the most devastating rice pathogens in China, as well as other rice-growing areas. Autophagy is an important process in normal cell differentiation and development among various organisms. To date, there has been no optimized experimental system introduced for the study of autophagy in U. virens. In addition, the function of autophagy in pathogenesis remains unknown in U. virens. Therefore, the functional analyses of UvAtg8 may potentially shed some light on the regulatory mechanism and function of autophagy in U. virens. Results: In this study, we characterized the functions of UvAtg8, which is a homolog of Saccharomyces cerevisiae ScAtg8, in the rice false smut fungus U. virens. The results showed that UvATG8 is essential for autophagy in U. virens. Also, the GFP-UvATG8 strain, which could serve as an appropriate marker for monitoring autophagy in U. virens, was generated. Furthermore, this study found that the ΔUvatg8 mutant was defective in the vegetative growth, conidiation, adaption to oxidative, hyperosmotic, cell wall stresses, and production of toxic compounds. Pathogenicity assays indicated that deletion of UvATG8 resulted in significant reduction in virulence of U. virens. Further microscopic examinations of the infection processes revealed that the severe virulence defects in the ΔUvatg8 were mainly caused by the highly reduced conidiation and secondary spore formation. Conclusions: Our results indicated that the UvAtg8 is necessary for the fungal growth, stresses responses, conidiation, secondary spore formation, and pathogenicity of U. virens. Moreover, our research finding will potentially assist in further clarifying the molecular mechanism of U. virens infection, as well as provide a good marker for autophagy in U. virens and a good reference value for the further development of effective fungicides based on gene targeting.

Genome-Wide Identification and Functional Characterization of CCHC-Type Zinc Finger Genes in Ustilaginoidea virens

“…This led to the functional identification of various pathogenic genes in U. virens, including iUvt3277, UvCom1, UvPRO1, UvAc1, UvPdeH, SCRE1, SCRE2 (UV_1261), UvBI-1, UvPmk1, UvCDC2, UvCdc3, UvCdc10, UvCdc11, UvCdc12, UvPal1, UvHox2, UvRpd3, UvSlt2, UvATG8, UvZnFTF1, UvMSN2, UvCGBP1, and UvEC1. These genes play important roles in the hyphal growth, conidiation, stress responses, and virulence of U. virens [46][47][48][49][50][51][52][53][54][55]. In the current study, we identified and functionally characterized CCHC-type zinc-finger proteins in U. virens.…”

Quantitative Proteomics Analysis Reveals the Function of the Putative Ester Cyclase UvEC1 in the Pathogenicity of the Rice False Smut Fungus Ustilaginoidea virens

“…The cellular morphogenetic protein UvPal1 affects hyphal growth, cell morphology, stress adaptation and virulence, and UvPal1 physically interacts with the cell division control protein UvCdc11 (also called septin) to mediate the formation of the septin complex to maintain cellular morphology and virulence [ 12 ]. Autophagy 8 (UvAtg8)-mediated autophagy plays important roles in growth, stress responses, production of toxic compounds, conidiation, secondary spore formation and pathogenicity in U. virens [ 37 ]. The histone deacetylase UvRpd3 and the mitogen-activated protein kinase (MAPK) UvSlt2 affect U. virens virulence , and both proteins interact to remove 2-hydroxyisobutyrylation and acetylation marks from UvSlt2 [ 38 ].…”

SUN-Family Protein UvSUN1 Regulates the Development and Virulence of Ustilaginoidea virens

“…The 1010 bp upstream and 996 bp downstream flanking sequences of Uvsun1 were amplified with primer pairs of S1F/S1R and S2F/S2R, respectively, and fused with the 1396 bp hygromycin-resistance cassette ( Hph ) (amplified with primers: HF and HR) from pSK1044 ( Yu et al, 2015 ) by ClonExpress TM MultiS One Step Cloning Kit (Vazyme) to the pMD19-T vector (Takara). Protoplast preparation and recovery of hygromycin-resistant transformants were performed as described previously ( Guo et al, 2019 ; Meng et al, 2020 ). For complementation, a fragment containing the entire Uvsun1 gene and its native promoter region (upstream 1.5 kb sequence) were amplified with primer pairs of pKO1-SC1F/pKO1-SC1R.…”

“…Step Cloning Kit (Vazyme) to the pMD19-T vector (Takara). Protoplast preparation and recovery of hygromycin-resistant transformants were performed as described previously (Guo et al, 2019;Meng et al, 2020). For complementation, a fragment containing the entire Uvsun1 gene and its native promoter region (upstream 1.5 kb sequence) were amplified with primer pairs of pKO1-SC1F/ pKO1-SC1R.…”

“…The “pears and lemons” protein UvPal1 physically interacted with UvCdc11 to mediate the septin complex to maintain the cellular morphology and virulence of U. virens ( Chen et al, 2020b ). Putative phosphatase UvPsr1 and UvAtg8-mediated autophagy were also required for mycelial growth, conidiation, stress response and pathogenicity ( Meng et al, 2020 ; Xiong et al, 2020 ). These results provide an important theoretical basis for understanding the molecular mechanisms of U. virens .…”