Cloning and expression analysis of the CyfaSTK gene from Cymbidium faberi

The cDNA sequence of the CyfaSTK gene (GenBank accession number:MH917915.1) was cloned from the flower bud of Cymbidium faberi Rolfe by homologous cloning. Results showed that the gene was 843 bp in length and the open reading frame (ORF) was 705 bp long, encoding a total of 234 amino acids and a stop codon. Molecular phylogenetic analysis and homologous protein comparison showed that the CyfaSTK protein belonged to the transcription factor STK-like evolution line of the AG subfamily of the D-class MADS-box gene family, which contained four distinct domains of MADS, I, K, and C terminal. The C terminal transcriptional activation region contained two conserved motifs:i.e., AG motifⅠ and AG motifⅡ. In addition, there was also a relatively conserved MD motif in Asparagales plants. Tissue specificity analysis showed that the C. faberi CyfaSTK gene was expressed in sepals, petals, lips, anther caps, gynostemia, and ovaries, but not in juvenile leaves. Expression of the C. faberi CyfaSTK gene in the ovary was significantly higher than that in other tissues. Among the dynamic changes in the flower bud at different developmental stages, the expression of CyfaSTK was the highest at the germination stage after dormancy and increased on the day of flowering. These results suggest that the D-class CyfaSTK gene not only regulates organ development in C. faberi, but also plays an important role in the normal development of the gynostemium and ovary.