ChZF7, a C3H zinc finger protein derived from alkaliphilic microalgae, improves alkaline stress tolerance in poplar via modulating flavonoid and hormone metabolism

Soil alkalinity severely restricts plant growth, especially woody plants such as poplar. In this study, we identified ChZF7, a C3H-type zinc finger protein from alkaliphilic microalgae Chlorella sp. BLD, and explored its function in improving alkaline stress tolerance in Shanxin poplar ( Populus davidiana × P. bolleana ). Under alkaline stress, ChZF7 overexpression lines displayed superior growth status, reduced electrolyte leakage and less reactive oxygen species (ROS) accumulation relative to WT plants. Transcriptomic and metabolomic analyses revealed that ChZF7 induces extensive metabolic reprogramming in poplar. Differentially expressed genes and accumulated metabolites were primarily enriched in the flavonoid biosynthesis pathway, along with the upregulation of genes and increased metabolites in the ABA biosynthetic pathway. Collectively, our results demonstrate that ChZF7 positively enhances alkaline tolerance in poplar by coordinating antioxidant metabolism, flavonoid metabolism and hormone metabolism. This work provides novel insights into alkaline stress adaptation mechanisms of woody plants, and highlights microalgae-derived zinc finger proteins as promising genetic resources for improving stress resistance in forest trees.