Induction of apoptosis‐like cell death and clearance of stress‐induced intracellular protein aggregates: dual roles for Ustilago maydis metacaspase Mca1

Abstract

Metacaspases primarily associate with induction and execution of programmed cell death in protozoa, fungi and plants. In the recent past, several studies have also demonstrated cellular functions of metacaspases other than cell death in different organisms including yeast and protozoa. This study shows similar dual function for the only metacaspase of a biotrophic phytopathogen, Ustilago maydis. In addition to a conventional role in the induction of cell death, Mca1 has been demonstrated to play a key role in maintaining the quality of the cellular proteome. On one hand, Mca1 could be shown to bring about apoptosis-like phenotypic changes in U. maydis on exposure to oxidative stress, on the other hand, the protein was found to regulate cellular protein quality control. U. maydis metacaspase has been found to remain closely associated with the insoluble intracellular protein aggregates, generated during an event of stress exposure to the fungus. The study, therefore, provides direct evidence for a role of U. maydis metacaspase in the clearance of the stress-induced intracellular insoluble protein aggregates. Furthermore, host infection assays with mca1 deletion strain also revealed a role of the protein in the virulence of the fungus.

Ustilago maydis secreted T2 ribonucleases, Nuc1 and Nuc2 scavenge extracellular RNA

“…Among these virulence factors, some are expressed only during host invasion and provide quantitative advantages to the pathogen during survival in planta. These are often referred to as effector proteins (Mukherjee et al, 2017). Effector proteins belong to different functional classes and contribute to the diversity of infection strategies adopted by the phytopathogen to establish infection.…”

“…Generation of the nuc1 and nuc2 complementation cassettes involved cloning of UMAG_02611 and UMAG_03023 gene sequences respectively within XbaI and EagI sites of p123‐P otef ‐ mcherry‐HA (Mukherjee, Gupta, Saran, Datta, & Ghosh, 2017). This also resulted in the construction of the nuc1 and nuc2 overexpression constructs p123‐P otef ‐ UMAG_02611‐HA and p123‐P otef ‐ UMAG_03023‐HA respectively.…”

Acetate provokes mitochondrial stress and cell death in Ustilago maydis

“…Recently, Mukherjee et al . (), showed the involvement of a metacaspase Mca1 in cell death, protein quality control and virulence for U. maydis .…”

Role of two metacaspases in development and pathogenicity of the Rice Blast fungus,Magnaporthe oryzae

“…Specifically, the ubiquitination of Yca1 was shown to have a direct impact on its function within the proteostasis network; once Yca1 was ubiquitinated, the yeast was able to regulate protein aggregation levels and autophagy (13). Metacaspases have also been discovered in a few other fungi groups like Aspergillus spp., Podospora anserina, Candida albicans and recently in the corn smut, Ustilago maydis (14)(15)(16)(17)(18). Like (which was not certified by peer review) is the author/funder.…”

“…The copyright holder for this preprint this version posted December 11, 2020. ; https://doi.org/10.1101/2020.12.10.420794 doi: bioRxiv preprint Yca1 in yeast, most of these fungal caspases have been linked to stress and agerelated responses as consequences of several environmental stimuli (14)(15)(16)(17)(18).…”