Genome-Wide Identification and Expression Analysis of the Cucumber FKBP Gene Family in Response to Abiotic and Biotic Stresses.

The FKBP (FK506-binding protein) gene family is an important member of the PPlase protease family and plays a vital role during the processes of plant growth and development. However, no studies of the FKBP gene family have been reported in cucumber. In this study, 19 FKBP genes were identified in cucumber, which were located on chromosomes 1, 3, 4, 6, and 7. Phylogenetic analysis divided the cucumber FKBP genes into three subgroups. The FKBP genes in the same subgroup exhibited similar structures and conserved motifs. The -acting elements analysis revealed that the promoters of cucumber FKBP genes contained hormone-, stress-, and development-related -acting elements. Synteny analysis of the FKBP genes among cucumber, , and rice showed that 12 kinds of syntenic relationships were detected between cucumber and FKBP genes, and 3 kinds of syntenic relationships were observed between cucumber and rice FKBP genes. The tissue-specific expression analysis showed that some FKBP genes were expressed in all tissues, while others were only highly expressed in part of the 10 types of tissues. The expression profile analysis of cucumber FKBP genes under 13 types of stresses showed that the gene was differentially expressed under abiotic stresses (high temperature, NaCl, silicon, and photoperiod) and biotic stresses (downy mildew, green mottle mosaic virus, wilt, , angular leaf spot, and root-knot nematode), which indicated that the gene plays an important role in the growth and development of cucumber. The interaction protein analysis showed that most of the proteins in the FKBP gene family interacted with each other. The results of this study will lay the foundation for further research on the molecular biological functions of the cucumber FKBP gene family.