Identification of Key Genes Controlling Sugar and Organic Acid Accumulation in Wampee Fruit (<i>Clausena lansium</i>) via Genome Assembly and Genome-wide Association Analysis

Wampee (<i>Clausena lansium</i>) is an economically significant subtropical fruit tree widely cultivated in Southern China. To provide high-quality genomic resources for <i>C. lansium</i>, we report a chromosome-level genome sequence for the "JinFeng" cultivar. The 297.1 Mb <i>C. lansium</i> genome contained nine chromosomes with a scaffold N50 of 29.2 Mb and encoded 23,468 protein-coding genes. Selective sweep analysis between sweet and sour <i>C. lansium</i> varieties and genome-wide association analysis identified 14 candidate genes putatively involved in sugar and acid accumulation. <i>ClERF061</i>, encoding an ethylene response factor, and <i>ClSWEET7</i>, encoding a Sugars Will Eventually be Exported Transporters (SWEET) family protein, were proposed as key regulators of the sweet and sour tastes of the wampee fruit. <i>ClERF061</i> and <i>ClSWEET7</i> overexpression in tomatoes increased the total sugar and acid content in fruits. <i>ClSWEET7</i> promoter activation by ClERF061 was confirmed via <i>Nicotiana benthamiana</i> transient expression. Our study provides valuable genomic resources for <i>C. lansium</i> genetics and breeding.