Gene Structural Specificity and Expression of MADS-Box Gene Family in Camellia chekiangoleosa

genes encode transcription factors that affect plant growth and development. is an oil tree species with ornamental value, but there have been few molecular biological studies on the developmental regulation of this species. To explore their possible role in and lay a foundation for subsequent research, 89 genes were identified across the whole genome of for the first time. These genes were present on all the chromosomes and were found to have expanded by tandem duplication and fragment duplication. Based on the results of a phylogenetic analysis, the 89 genes could be divided into either type I (38) or type II (51). Both the number and proportion of the type II genes were significantly greater than those of and , indicating that type II genes experienced a higher duplication rate or a lower loss rate. The results of both a sequence alignment and a conserved motif analysis suggest that the type II genes are more conserved, meaning that they may have originated and differentiated earlier than the type I genes did. At the same time, the presence of extra-long amino acid sequences may be an important feature of . Gene structure analysis revealed the number of introns of genes: twenty-one type I genes had no introns, and 13 type I genes contained only 1~2 introns. The type II genes have far more introns and longer introns than the type I genes do. Some MIKC genes have super large introns (≥15 kb), which are rare in other species. The super large introns of these MIKC genes may indicate richer gene expression. Moreover, the results of a qPCR expression analysis of the roots, flowers, leaves and seeds of showed that the genes were expressed in all those tissues. Overall, compared with that of the type I genes, the expression of the type II genes was significantly higher. The and genes (type II) were highly expressed specifically in the flowers, which may in turn regulate the size of the flower meristem and petals. was expressed specifically in the seeds, which might affect seed development. This study provides additional information for the functional characterization of the gene family and lays an important foundation for in-depth study of related genes, such as those involved in the development of the reproductive organs of .