Functional Characterization of the β-Amyrin Synthase Gene Contributing to Cuticular Wax Variation Between Two Blueberry Types.

Cuticular wax plays a critical role in preserving fruit quality and providing structural protection against external stresses in plants. Rabbiteye blueberry and southern highbush blueberry are the main types of cultivated blueberries grown in southern China, exhibiting substantial differences in fruit ripening, management requirements, and stress resistance. In this study, rabbiteye blueberry cv. Titan and southern highbush blueberry cv. Emerald were examined to assess variation in cuticular wax and to functionally characterize candidate genes involved in β-amyrin synthesis. The wax matrix of both types comprised fatty acids, alkanes, primary alcohols, ketones, esters, and triterpenes, with triterpenes constituting a major functional component. β-amyrin was the predominant triterpenoid, accounting for 63.1% and 86.1% of total triterpenes in Titan and Emerald, respectively. A comprehensive analysis of β-amyrin synthase genes (BASs) was conducted, and their phylogenetic relationships, gene structures, and chromosomal localization were studied. RNA-seq profiling identified VaBAS355 as a key candidate gene, and its expression pattern and subcellular localization were subsequently evaluated. The heterologous and homologous transient expression of VaBAS355 resulted in increased β-amyrin accumulation in tobacco and blueberry. Taken together, our results provide a foundation for elucidating the functional roles of BASs and their regulatory mechanisms, especially in the processes of fruit development and resistance to environmental stresses.