Genome-Wide Identification and Expression Profiling Analysis of WOX Family Protein-Encoded Genes in Triticeae Species

The WOX family is a group of plant-specific transcription factors which regulate plant growth and development, cell division and differentiation. From the available genome sequence databases of nine Triticeae species, 199 putative WOX genes were identified. Most of the identified WOX genes were distributed on the chromosomes of homeologous groups 1 to 5 and originated via the orthologous evolution approach. Parts of WOX genes in Triticum aestivum were confirmed by the specific PCR markers using a set of Triticum. durum-T. aestivum genome D substitution lines. All of these identified WOX proteins could be grouped into three clades, similar to those in rice and Arabidopsis. WOX family members were conserved among these Triticeae plants; all of them contained the HOX DNA-binding homeodomain, and WUS clade members contained the characteristic WUS-box motif, while only WUS and WOX9 contained the EAR motif. The RNA-seq and qPCR analysis revealed that the TaWOX genes had tissue-specific expression feature. From the expression patterns of TaWOX genes during immature embryo callus production, TaWOX9 is likely closely related with the regulation of regeneration process in T. aestivum. The findings in this study could provide a basis for evolution and functional investigation and practical application of the WOX family genes in Triticeae species.