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The miRNAs and their targets involved in senescence of strawberry fruit (Fragaria ananassa L. cv. Zhangji) were analyzed in the present study. In the previous work, three members of miR164 family, mdmmiR164d_ 1ss21AC, mdm-miR164e and mdm-miR164f_1ss21TA, and three of their targets, NAC domain transcriptional regulator superfamily protein, NAC domain containing protein 38 and NAC domain containing protein 87 had been identified by high-throughput sequencing and degradome analysis. In the process of fruit senescence from 0 to 48 h at 4°C storage, the relative levels of mdm-miR164e and mdmmiR164d_1ss21AC expression were significantly increased resulting in decreased expression of NAC genes, and delayed senescence of strawberry fruits. These results suggested that miR164 was involved in strawberry fruit senescence by negatively mediating the expression of NAC transcription factors.

One novel transcription factor gene DnWRKY29 was isolated from Dendrobium officinale, and its functions were identified by its overexpression in tobacco. Compared to the wild type (WT), the DnWRKY29 transgenic tobacco seeds and seedlings showed more sensitivity to salt and drought stresses. The seed germination rate, seedling root length, and fresh weight of transgenic tobacco were lower than in WT. The activities of peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) in transgenic tobacco were decreased, and the content of malondialdehyde (MDA) in transgenic tobacco was increased. Moreover, the expression of DnWRKY29 was up-regulated in Dendrobium seedlings under salt and drought stresses, which was consistent with the function identified by its overexpression in tobacco, indicating that the up-regulation or overexpression of DnWRKY29 impaired plant tolerance to salt and drought stresses. These results provided a new insight to the low tolerance of Dendrobium seedlings to environmental change.

Proton (H+) and aluminum (Al3+) toxicities are major factors limiting crop production on acid soils. To study whether salicylic acid (SA) is functional in alleviating protein damage caused by H+ and Al3+ toxicities, an investigation of the antioxidant defense response regulated by SA was carried out on barley (Hordeum vulgare L.) seedlings under H+, Al3+, and combined stresses. It was found that the relative root elongation of seedlings, which grew in the solutions supplemented with SA, was significantly higher than that of seedlings without SA treatment after 24-h treatments with H+, Al3+, and combined stresses. The lesser amount of carbonylated proteins with molecular weights ranging from 14.4 to 97 kD, was accumulated in seedlings treated with SA than that in the seedlings without SA treatment. The higher activities of antioxidant enzymes and lesser content of MDA were observed in seedlings treated with SA compared with the seedlings without SA treatment. Moreover, the nitroblue tetrazolium staining of roots showed that ROS accumulation was decreased by SA treatments. This study suggested that SA could alleviate cell damage caused by H+ and Al3+ toxicities on acid soils by both activating antioxidant defense responses and reducing the contents of carbonylated proteins caused by ROS in barley seedlings.