As the first defence for cells to counteract the toxicity of active oxygen, superoxide dismutase (SOD) plays an important role in the response of living organisms to stress and cell differentiation. One extracellular Cu-ZnSOD (ecCu-ZnSOD), and two MnSODs, were identified based on the Volvariella volvacea genome sequence. All three genes have complicated alternative splicing modes during transcription; only when the fourth intron is retained can the Vv_Cu-Znsod1 gene be translated into a protein sequence with SOD functional domains. The expression levels of the three sod genes in the pilei are higher than in the stipe. The Vv_Cu-Znsod1 and the Vv_Mnsod2 are co-expressed in different developmental stages of the fruiting body, with the highest level of expression in the pilei of the egg stage, and they show a significant, positive correlation with the efficiency of karyogamy, indicating the potential role of these two genes during karyogamy. The expression of the ecCu-Znsod and two Vv_Mnsod genes showed a significant up-regulated when treated by cold stress for one hour; however, the lack of the intracellular Cu-ZnSOD encoding gene (icCu-Znsod) and the special locus of the ecCu-Znsod gene initiation codon suggested a possible reason for the autolysis phenomenon of V. volvacea in cold conditions.
Keywords: alternative splicing modes; cold stress; fruiting-body development; gene differential expression; straw mushroom.