Article

Plant Molecular Biology

, Volume 54, Issue 3, pp 353-372

First online:

Members of a New Group of Chitinase-Like Genes are Expressed Preferentially in Cotton Cells with Secondary Walls

  • Deshui ZhangAffiliated withDepartment of Biological Sciences, Texas Tech UniversityDepartment of Crop Science and Dept. of Botany, North Carolina State University
  • , Maria HrmovaAffiliated withFaculty of Sciences, School of Agriculture and Wine, and the Australian Centre for Plant Functional Genomics, University of Adelaide
  • , Chun-Hua WanAffiliated withDepartment of Biological Sciences, Texas Tech UniversityContent Systems, Celera Genomics
  • , Chunfa WuAffiliated withDepartment of Biological Sciences, Texas Tech UniversityDepartment of Microbiology, Texas Tech University Health Sciences Center
  • , Jace BalzenAffiliated withDepartment of Biological Sciences, Texas Tech University
  • , Wendy CaiAffiliated withDepartment of Biological Sciences, Texas Tech University
  • , Jing WangAffiliated withDepartment of Biological Sciences, Texas Tech UniversityPlant Stress and Water Conservation Laboratory
  • , Llewellyn D. DensmoreAffiliated withDepartment of Biological Sciences, Texas Tech University
  • , Geoffrey B. FincherAffiliated withFaculty of Sciences, School of Agriculture and Wine, and the Australian Centre for Plant Functional Genomics, University of Adelaide
    • , Hong ZhangAffiliated withDepartment of Biological Sciences, Texas Tech University
    • , Candace H. HaiglerAffiliated withDepartment of Biological Sciences, Texas Tech UniversityPlant Stress and Water Conservation Laboratory

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Abstract

Two homologous cotton (Gossypium hirsutum L.) genes, GhCTL1 and GhCTL2, encode members of a new group of chitinase-like proteins (called the GhCTL group) that includes other proteins from two cotton species, Arabidopsis, rice, and pea. Members of the GhCTL group are assigned to family GH19 glycoside hydrolases along with numerous authentic chitinases (http://afmb.cnrs-mrs.fr/CAZY/index.html), but the proteins have novel consensus sequences in two regions that are essential for chitinase activity and that were previously thought to be conserved. Maximum parsimony phylogenetic analyses, as well as Neighbor-Joining distance analyses, of numerous chitinases confirmed that the GhCTL group is distinct. A molecular model of GhCTL2 (based on the three-dimensional structure of a barley chitinase) had changes in the catalytic site that are likely to abolish catalytic activity while retaining potential to bind chitin oligosaccharides. RNA blot analysis showed that members of the GhCTL group had preferential expression during secondary wall deposition in cotton lint fiber. Cotton transformed with a fusion of the GhCTL2 promoter to the β-d-glucuronidase gene showed preferential reporter gene activity in numerous cells during secondary wall deposition. Together with evidence from other researchers that mutants in an Arabidopsis gene within the GhCTL group are cellulose-deficient with phenotypes indicative of altered primary cell walls, these data suggest that members of the GhCTL group of chitinase-like proteins are essential for cellulose synthesis in primary and secondary cell walls. However, the mechanism by which they act is more likely to involve binding of chitin oligosaccharides than catalysis.

cellulose chitin binding cotton fiber molecular modeling promoter activity secondary cell wall