PagWRKY12 promotes salt and drought tolerance in 84K poplar

Drought and salinization are paramount abiotic stresses major environmental factors limiting plant growth and development. WRKY, as a transcription factor, plays a key role in plants' stress responses to adverse environmental conditions. In this study, we identified a gene encoding a WRKY transcription factor from 84K poplar (Populus alba ×Populus glandulosa), whose expression was significantly upregulated under both salt stress and drought stress. Subcellular localization results showed that PagWRKY12 is located in the cell nucleus. Yeast hybridisation experiments confirmed that, although the encoded protein lacks self-activation activity, it can bind to G-box and W-box elements. Overexpression of PagWRKY12 markedly reduced plant height and root length, whilst enhancing tolerance to salt and drought stress in transgenic poplars by increasing Superoxide Dismutase (SOD), Peroxidase (POD) and proline content, and decreasing Malondialdehyde (MDA) and Hydrogen Peroxide (H₂O₂) levels. Transcriptome and RT-qPCR analyses indicated that PagWRKY12 overexpression in poplars enhanced expression of CYP87A2 and ATPIN4 genes involved in brassinosteroid (Br) biosynthesis, alongside AtMYB83 and CESA4 genes associated with secondary cell wall thickening (SCW). These findings suggest that PagWRKY12 may enhance salt and drought tolerance in 84K poplar by coordinating the promotion of Br biosynthesis and secondary cell wall thickening.