Genome-wide characterization and expression analysis of the CONSTANS-like gene family of <i>Juglans mandshurica</i> Maxim

The zinc-finger proteins encoded by the CONSTANS-like (COLs) gene family in <i>Juglans mandshurica</i> Maxim. play a significant role in regulating photoperiod-dependent flowering time, as well as in various processes such as growth and development. In this study, 15 members of the CONSTANS-like gene family were identified based on the genomic data of <i>Juglans mandshurica</i>. All of these proteins possess an N-terminal zinc-finger B-box domain and a C-terminal CCT domain. Phylogenetic analysis indicates that the <i>JmCOLs</i> proteins can be divided into three subgroups, with gene structures and motif compositions varying among these subgroups. Chromosomal analysis reveals that the 15 <i>JmCOLs</i> genes are distributed across nine chromosomes. The promoters of genes in this family contain stress-related cis-acting elements, hormone-related response elements, and other elements associated with growth and development. Notably, the most prominent elements are the light-responsive elements, suggesting that genes in this family are predominantly expressed in leaves. The expression patterns of <i>JmCOLs</i> genes differ among the members. Specifically, <i>JmCOL5</i> and <i>JmCOL10</i> are expressed exclusively in flower buds (<i>p</i> < 0.05). Throughout the 10 stages of flower bud development, the overall expression level of <i>JmCOL4a</i> peaks at approximately 50 to 100 times higher than its lowest point. The expression pattern of <i>JmCOL5</i>, which first reaches its maximum during the physiological differentiation stage of protogynous male flower buds before declining, suggests its potential involvement in the development of heteromorphic and dichogamous flowers.