Domain exchanges between KNAT3 and KNAT1 suggest specificity of the kn1-like homeodomains requires sequences outside of the third helix and N-terminal arm of the homeodomain.
Domain exchange constructs that traded regions surrounding the homeodomain were constructed for two kn1-like genes, KNAT1 and KNAT3, and introduced into Arabidopsis thaliana under the control of the 35S CaMV promoter. The kn1-like homeodomain proteins all have the homeodomain located near the C-terminus of the protein, and also share a second conserved domain (the ELK domain) immediately N-terminal to the homeodomain. Progeny were scored for the appearance of the KNAT1 overexpression phenotype. A construct containing the KNAT3 N-terminus and the KNAT1 ELK- and homeodomain resulted in a KNAT1 overexpression phenotype, indicating that specificity mainly resides within the ELK- and homeodomain region. Further exchanges demonstrated that specificity probably does not arise from a single region within the ELK and/or homeodomain but rather requires sequences both N-terminal and C-terminal to residue 23 of the homeodomain. Further, in contrast to some animal homeodomains, KNAT1 does not utilize the residues of the N-terminal arm of the homeodomain for specificity.
Serikawa
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KA
Department of Botany, University of Washington, Seattle 98195, USA. kyles@u.washington.edu
Zambryski
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PC
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D018398:Homeodomain Proteins / Q000737:chemistry* / Q000235:genetics*; D008969:Molecular Sequence Data; D015394:Molecular Structure; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics*; D030821:Plants, Genetically Modified; D017386:Sequence Homology, Amino Acid; D014170:Transformation, Genetic
D029681:Arabidopsis Proteins; D018398:Homeodomain Proteins; C092212:KNAT1 protein, Arabidopsis; C103245:KNAT3 protein, Arabidopsis; D010940:Plant Proteins