WUSCHEL-related Homeobox genes in Populus tomentosa: diversified expression patterns and a functional similarity in adventitious root formation

作   者：刘伯斌，王琳，张进，李建波，郑环泉，陈军，卢孟柱
期刊名称：BMC genomics
影响因子：4.041
卷 期 号：15(1)
页     码：396
关键词：
论文摘要：
Background: WUSCHEL (WUS)-related homeobox (WOX) protein family members play important roles in the
maintenance and proliferation of the stem cell niche in the shoot apical meristem (SAM), root apical meristem
(RAM), and cambium (CAM). Although the roles of some WOXs in meristematic cell regulation have been well
studied in annual plants such as Arabidopsis and rice, the expression and function of WOX members in woody plant
poplars has not been systematically investigated. Here, we present the identification and comprehensive analysis of
the expression and function of WOXs in Populus tomentosa.
Results: A genome-wide survey identified 18 WOX encoding sequences in the sequenced genome of Populus
trichocarpa (PtrWOXs). Phylogenetic and gene structure analysis revealed that these 18 PtrWOXs fall into modern/WUS,
intermediate, and ancient clades, but that the WOX genes in P. trichocarpa may have expanded differently from the
WOX genes in Arabidopsis. In the P. trichocarpa genome, no WOX members could be closely classified as AtWOX3,
AtWOX6, AtWOX7, AtWOX10, and AtWOX14, but there were two copies of WOX genes that could be classified as PtrWUS,
PtrWOX2, PtrWOX4, PtrWOX5, PtrWOX8/9, and PtrWOX11/12, and three copies of WOX genes that could be classified as
PtrWOX1 and PtrWOX13. The use of primers specific for each PtrWOX gene allowed the identification and cloning of
18 WOX genes from P. tomentosa (PtoWOXs), a poplar species physiologically close to P. trichocarpa. It was found
that PtoWOXs and PtrWOXs shared very high amino acid sequence identity, and that PtoWOXs could be classified
identically to PtrWOXs. We revealed that the expression patterns of some PtoWOXs were different to their Arabidopsis
counterparts. When PtoWOX5a and PtoWOX11/12a, as well as PtoWUSa and PtoWOX4a were ectopically expressed in
transgenic hybrid poplars, the regeneration of adventitious root (AR) was promoted, indicating a functional similarity
of these four WOXs in AR regeneration.
Conclusions: This is the first attempt towards a systematical analysis of the function of WOXs in P. tomentosa. A
diversified expression, yet functional similarity of PtoWOXs in AR regeneration is revealed. Our findings provide useful
information for further elucidation of the functions and mechanisms of WOXs in the development of poplars.