Characteristics of PwUSP1 in Picea wilsonii and its response to drought and salt stress

  Objective  Universal stress proteins (USP) are stress-related genes which are widely reported to participate in the process of abiotic-stress response of plants. By identifying and validating the function of PwUSP1, we revealed the role of PwUSP1 in plants under drought and salt stress, thereby providing candidate genes for improving the tolerance to abiotic stress through genetic engineering in Picea wilsonii.

  Method  Transient transformation of tobacco leaves was used to reveal the location of PwUSP1 in cells. Yeast two-hybrid experiment was used to determine whether PwUSP1 could form homodimers by itself. The Arabidopsis Col-0 (WT) was transferred by floral dip method to obtain homozygous PwUSP1 overexpression lines. The survival rates and water loss rates of PwUSP1 overexpression plants, wild type (WT) and empty vector (VC) were measured to analyze and compare the tolerance of different lines when plants were subjected to drought and salinity. DAB and NBT staining, the activities of SOD, POD, CAT and the content of MDA were determined to explore the potential physiological mechanism of PwUSP1 acting.

  Result  Subcellular localization results showed that PwUSP1 was located in the nucleus, cytoplasm and cell membrane. Besides, the yeast two hybrid experiment showed that PwUSP1 itself can form homodimers. qRT-PCR was used to detect transgenic Arabidopsis, and the results showed that two independent homozygous lines with stable overexpression (L1, L7) were successfully obtained for further analysis. Under drought or salt stress, compared with WT and VC, PwUSP1 overexpression lines significantly improved the drought or salt tolerance of plants, and showed higher survival rates and lower water loss rates. Furthermore, overexpression of PwUSP1 obviously reduced the content of H₂O₂ and O₂ ⁻, and simultaneously promoted the activities of antioxidant enzymes and inhibited the accumulation of MDA.

  Conclusion  PwUSP1 is located in the nucleus, cytoplasm and cell membrane, and can form homodimers by itself. Under drought or salt stress, PwUSP1 improves the tolerance to abiotic stress of plants by enhancing ROS scavenging ability and inhibiting membrane lipid peroxidation.