Identification and Expression Analysis of PeWOX5 and PeWOX13 Genes in Hybrid Poplar

Abstract

The WUSCHEL-related HOMEOBOX (WOX), a plant-specific transcription factor family, plays a crucial role in different plant tissues and at various developmental stages. To explore the expression patterns of WOX genes in Populus, we isolated and characterized two members of the WOX family, PeWOX5 and PeWOX13, from hybrid poplar (Populus deltoids × Populus euramericana). Gene structure analysis revealed that PeWOX5 had one intron, and PeWOX13 had two introns. PeWOX5 and PeWOX13 proteins comprised highly conserved homeodomains, and the PeWOX5 protein contained a WUS-box and ETHYLENE RESPONSE FACTOR-associated amphiphilic repression domains involved in transcriptional repression. Sequence and phylogenetic analyses showed that PeWOX5 belonged to a modern/WUS clade, and PeWOX13 belonged to an ancient clade. The subcellular localization assay indicated that both PeWOX5 and PeWOX13 were located in the nucleus. PeWOX5 had an obvious tissue-specific expression pattern, while PeWOX13 exhibited a ubiquitous expression pattern. These results suggest that PeWOX5 is mainly involved in the developmental regulation of Populus adventitious roots, whereas PeWOX13 may play various roles in the growth and development of different Populus tissues.