Chilling stress reduced protein translation by the ubiquitination of ribosomal proteins in Volvariella volvacea

Abstract

In Volvariella volvacea, an important edible mushroom species, cryogenic autolysis is a typical part of abnormal metabolism; however, the underlying mechanisms remain unclear. Ubiquitylome analysis revealed that chilling stress (CS) affected protein translation and degradation by ubiquitination. Comparative proteomics analysis showed that CS downregulated protein expression in V. volvacea V23 instead of VH3 (improved chilling stress resistance strain). The integrative ubiquitylome, proteomics, and transcriptome analyses indicated that CS reduced protein translation by the ubiquitination of ribosomal proteins. An activity assay of the 20S proteasome showed that CS decreased the degradation efficiency of the ubiquitin-proteasome system. UBEV2, one type of ubiquitin-conjugating enzyme E2 (UBE2) in V. volvacea, was upregulated after cold stress treatment using western blot analysis. GST pull-down experiments of UBEV2 provided evidence that CS affected protein translation by the ubiquitination of ribosomal proteins. Co-IP experiments confirmed that UBEV2 bound to the ubiquitinated SSB2, a ribosome-associated molecular chaperone. An anti-freezing experiment demonstrated that the UBE2 inhibitor could improve the cold stress resistance of V. volvacea. Our observations revealed that CS triggered ubiquitination-mediated autolysis associated with a decrease in protein translation and highlighted the mechanistic role of UBEV2 in facilitating cryogenic autolysis in V. volvacea. SignificanceVolvariella volvacea, the edible straw mushroom, is a highly nutritious food source widely cultivated on a commercial scale in tropical and subtropical regions. The challenges associated with the cryogenic autolysis preservation of V. volvacea have limited its marketability. This issue of cryogenic autolysis is both an interesting scientific problem to solve and a practical economic matter. Integrative ubiquitylome, proteomics, and transcriptome analyses, together with GST pulldown and Co-IP experiments, indicated that chilling stress reduced protein translation by the ubiquitination of ribosomal proteins in V. volvacea. This study significantly contributes to our understanding of ubiquitination-mediated autolysis associated with a decrease in protein translation in V. volvacea. Our data highlight the mechanistic role of UBEV2 in facilitating the cryogenic autolysis of V. volvacea. We provided a new idea for the preservation of V. volvacea by inhibiting UBEV2 to increase its marketability.