24-Epibrassinolide-alleviated drought stress damage influences antioxidant enzymes and autophagy changes in peach (Prunus persicae L.) leaves

Drought stress is a serious threat to agriculture and the environment. Brassinosteroids (BRs) increase tolerance to drought stress of plant. Autophagy plays important roles in plant responses to drought stress; however, there are few reports on autophagy in peach (Prunus persica). In total, 23 putative autophagy-related genes (ATGs) in peach were identified using ATGs from the Arabidopsis thaliana genome as query in BLASTx algorithm-based searches. Under drought stress, the photosynthetic abilities of peach leaves decreased, while antioxidant enzyme activities, autophagy and ATG expression increased. A correlation analysis showed that antioxidant enzyme activities are inversely correlated to the expression levels of the PpATGs. During drought, the PpATG8s and some PpATG18s had the strongest responses. To investigate enhanced drought-stress tolerance, peach was treated with water, 100 nM 24-epibrassinolide (EBR), 1 mu M EBR, 10 mu M EBR and 1 mu M voriconazole. Exogenous EBR at 1 mu M decreased the malondialdehyde (MDA) content under drought stress when compared with water-, 1 mu M voriconazole-, 100 nM EBR- and 10 mu M EBR-treated peach leaf. The 1-mu M EBR application increased superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX) and glutathione peroxidase (GR) activities during drought stress. In addition, the expression levels of PpATGs were inhibited by EBR. Thus, the 1-mu M EBR treatment alleviated drought-stress damage to peach leaves, decreased PpATG expression levels and reduced the number of autophagosomes.