Identification and responding to exogenous hormone of HB-KNOX family based on transcriptome data of Caucasian clover.

Caucasian clover (Trifolium ambiguum M. Bieb.) is a strongly rhizomatous, low-crowned perennial leguminous and ground-covering grass. The species is resistant to cold, arid temperatures and grazing due to a well-developed underground rhizome system and a strong clonal reproduction capacity. KNOTTED1-LIKE HOMEOBOX (KNOX) genes are a family of plant-specific homeobox transcription factors with important roles in plant development. Preliminary transcriptome analysis enabled us to understand the gene expression in five different tissues, which helped us to screen the predetermined genes of the HB-KNOX family genes for the rhizome growth and development of Caucasian clover. The study identified 41 TaKNOX genes from the Caucasian clover transcriptome database. Gene length, MW and pl of TaKNOX family transcription factors varied, but the gene structure and motifs were relatively conserved in bioinformatics analysis. Phylogenetic analyses of Arabidopsis thaliana, soybean, Medicago truncatula and Caucasian clover were performed to study the evolutionary and functional relationships in various species. Prediction and verification of the subcellular localizations revealed the diverse subcellular localization of these 41 TaKNOX proteins. The expression profile of exogenous hormones showed that the TaKNOX gene showed multiple expression regulation patterns, and was involved in 6-BA, IAA and KT signaling pathways. Our results reveal the characteristics of the TaKNOX gene family, thus laying a foundation for further functional analysis of the KNOX family in Caucasian clover.