Original Paper

Tree Genetics & Genomes

, Volume 8, Issue 1, pp 177-194

First online:

Evolution and divergence in the coding and promoter regions of the Populus gene family encoding xyloglucan endotransglycosylase/hydrolases

  • Xia YeAffiliated withCollege of Horticulture, Henan Agricultural UniversityDepartment of Plant Sciences, University of Tennessee
  • , Suhua YuanAffiliated withDepartment of Plant Sciences, University of TennesseeInstitute for Plant Genomics and Biotechnology, Texas A&M University
  • , Hong GuoAffiliated withDepartment of Biochemistry, Cellular and Molecular Biology, University of Tennessee
  • , Feng ChenAffiliated withDepartment of Plant Sciences, University of TennesseeBioenergy Science Center, Oak ridge National Laboratory
  • , Gerald A. TuskanAffiliated withEnvironmental Science Division, Oak Ridge National LaboratoryBioenergy Science Center, Oak ridge National Laboratory
  • , Zong-Ming ChengAffiliated withDepartment of Plant Sciences, University of TennesseeBioenergy Science Center, Oak ridge National Laboratory Email author 

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Xyloglucan endotransglycosylase/hydrolases (XTHs) are believed to modify the cell wall structure by cleaving a xyloglucan polymer and transferring the newly generated, potentially reducing, terminal to another xyloglucan. We report here the detailed analysis of 37 Populus trichocarpa XTH genes/proteins in their divergence in both the coding and 5′ promoter regions. Our results show that the Populus XTH genes have experienced whole-genome and local duplications and pre- and post-speciation divergence. Genome-wide and segmental duplications seem to be dominant in subfamily I and III, while tandem duplication seems to be the major mechanism for the subfamily II expansion, which also has higher average ratios of K a/K s compared to those in subfamily I and III. There was a general lack of organ-specific gene expression. In contrast, the expression patterns in subfamily II varied in response to various hormone treatments, with II-A being up-regulated and II-B down-regulated after 2 h of hormone treatment. Expression for this subfamily was verified using the 1.5-kb PtXTH22 promoter that was fused with the GUS reporter gene and transformed into Arabidopsis. The PtXTH22 promoter contains auxin response element, ethylene insensitive 3-like factors, and brassinosteroid response cis-elements. Histochemical GUS staining of transgenic Arabidopsis seedlings confirmed that the PtXTH22 promoter was up-regulated by several hormones.


Xyloglucan endotransglycosylase/hydrolases (XTHs) Gene duplications and divergence Gene expression Populus Arabidopsis