Responses of Antioxidant Enzymes, Osmoregulators and Their Related Genes to Drought Stress and Rehydration in Auricularia fibrillifera

Abstract

The antioxidases, osmoregulators and related gene responses to drought stress and rehydration were investigated to understand drought-tolerance mechanisms in Auricularia fibrillifera. Compared with in the sensitive cultivar HSQ, the three enzyme activities in resistant cultivar CSLZ significantly increased during drought stress. Drought stress generally increased the contents osmoregulators in both cultivars. The soluble sugar, soluble amino acid and proline contents in CSLZ exhibited significant increases compared with in HSQ under untreated control conditions. The enzyme activities and osmoprotectant contents in both cultivars decreased rapidly at 24 h after rehydration. These enzymes and osmoprotectants had key roles in responses to primary and severe drought stresses in CSLZ, respectively. Compared with in HSQ, the soluble sugar content in CSLZ showed the greatest increase under 50% and 60% of water loss conditions, followed by the superoxide dismutase activity and then the proline content. In total, 52,954 unigenes were obtained using the transcriptome analysis, which included many key differentially expressed genes involved in the responses to oxidative and osmotic stresses under drought conditions. The expression levels of these genes were generally consistent with the enzyme activities or osmoregulator contents under drought-stress and rehydration conditions, respectively. The defense-related pathways were also enriched under drought-stress conditions. Thus, these enzymes and osmoregulators may form a defense network to protect Auricularia against drought-related damage. Resistant CSLZ had stronger abilities to maintain higher enzyme activity levels and synthesize osmoprotectants, which confer drought resistance, than sensitive HSQ.