Genome-Wide Identification of CONSTANS-like (COL) Gene Family and the Potential Function of ApCOL08 Under Salt Stress in Andrographis paniculata

<i>Andrographis paniculata</i> is an important medicinal herb known as a "natural antibiotic", which has been used in Southeast Asia for thousands of years. The <i>CONSTANS-like</i> (<i>COL</i>) gene is an important regulatory factor for plant photoperiod flowering and stress response. However, there is currently no detailed research on the <i>COL</i> genes of <i>A. paniculata</i>. In our study, we performed a genome-wide analysis of <i>A. paniculata COL</i> (<i>ApCOL</i>) family members using bioinformatics tools and identified nine <i>ApCOL</i> genes. Based on phylogenetic analysis, <i>ApCOL</i>s were categorized into three groups, with members of the same group having similar structures. Gene duplication events indicated that only one pair of duplicated genes was identified, possibly caused by segmental duplication. In terms of evolutionary relationships, the COL proteins of <i>A. paniculata</i> and <i>Sesamum indicum</i> were closely related, showing that they are highly similar in the phylogenetic tree. In addition, <i>ApCOL</i> genes showed tissue specificity and were specifically highly expressed mainly in leaves and flowers. Based on the cis-regulatory element prediction results, we examined the expression levels of <i>ApCOL</i>s under hormone and salt stress, and <i>ApCOL08</i> was significantly induced. With subcellular localization results consistent with the prediction, we transformed <i>ApCOL08</i> into yeast and showed significant resistance to salt stress. Our study suggests that <i>ApCOL</i> genes have important roles in response to abiotic stress and plant development and initially identifies key genes for future molecular regulation studies.