Qing Guo

Extreme environments, especially drought and high salt conditions, seriously affect plant growth and development. Ethylene-responsive factor (ERF) transcription factors play an important role in salt stress response. In this study, a significantly upregulated ERF gene was identified in 84K (Populus alba × P. glandulosa), which was named PagERF072. PagERF072 was confirmed to be a nuclear-localized protein. The results of yeast two-hybrid (Y2H) assay showed that PagERF072 protein exhibited no self-activating activity, and yeast one-hybrid (Y1H) demonstrated that PagERF072 could specifically bind to GCC-box element. Under salt stress, the transgenic poplar lines overexpressing PagERF072 showed improved salt tolerance. The activities of peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT) in transgenic poplars were significantly increased relative to those of wild-type (WT) plants, whereas malondialdehyde (MDA) content showed an opposite trend. In addition, reactive oxygen species (ROS) was significantly reduced, and the expression levels of POD- and SOD-related genes were significantly increased in transgenic poplars under salt stress compared with WT. All results indicate that overexpression of the PagERF072 gene can improve the salt tolerance of transgenic poplars.

SQUAMOSA promoter binding protein (SBP) is a kind of plant-specific transcription factor, which plays a crucial role in stress responses and plant growth and development by activating and inhibiting the transcription of multiple target genes. In this study, a total of 30 SBP genes were identified from Populus trichocarpa genome and randomly distributed on 16 chromosomes in poplar. According to phylogenetic analysis, the PtSBPs can be divided into six categories, and 14 out of the genes belong to VI. Furthermore, the SBP genes in VI were proved to have a targeting relationship with miR156. The homeopathic element analysis showed that the promoters of poplar SBP genes mainly contain the elements involved in growth and development, abiotic stress and hormone response. In addition, there existed 10 gene segment duplication events in the SBP gene duplication analysis. Furthermore, there were four poplar and Arabidopsis orthologous gene pairs among the poplar SBP members. What is more, poplar SBP gene family has diverse gene expression pattern under salt stress. As many as nine SBP members were responding to high salt stress and six members possibly participated in growth development and abiotic stress. Yeast two-hybrid experiments indicated that PtSBPs can form heterodimers to interact in the transcriptional regulatory networks. The genome-wide analysis of poplar SBP family will contribute to function characterization of SBP genes in woody plants.