Genome-Wide Characterization of SnRK Gene Family in Mangrove Plant Avicennia marina and Function of AmSnRK2.7-AmENO2 Module in Response to Salinity.

Sucrose non-fermenting-1-related protein kinase (SnRK) is a plant serine/threonine kinase that mediates stress signaling, yet its function in the mangrove Avicennia marina remains unexplored. In this study, we identified 46 SnRK genes in A. marina, classifying them into three subfamilies with high phylogenetic conservation. Family expansion occurred mainly through 20 segmental duplication events under purifying selection (Ka/Ks < 1). Promoter regions were enriched in stress- and hormone-responsive elements, and expression profiling showed distinct tissue-specific and stress-responsive patterns. Our study specifically focused on the functional characterization of AmSnRK2.7. AmSnRK2.7-overexpressed Arabidopsis thaliana increases salt tolerance by altering the expression of ion transport genes and mediating Na+ efflux from the roots. Further investigation revealed that AmSnRK2.7 interacts with and phosphorylates AmENO2 (enolase, a key enzyme in the glycolysis pathway). Meanwhile, measurements of ATP content in wild type, AmSnRK2.7-overexpressed Arabidopsis lines and the atsnrk2.6 (homologous gene of AmSnRK2.7 in A. thaliana) mutant confirm that the AmSnRK2.7-AmENO2 module can affect the energy-driven Na+ efflux. Our findings provide key insights into the role of SnRK gene family in mangrove adaptation to saline intertidal habitat, and suggest AmSnRK2.7-AmENO2 module plays a role in salt tolerance.