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Gene Review

GL2  -  homeobox-leucine zipper protein GLABRA 2

Arabidopsis thaliana

Synonyms: F19K16.20, F19K16_20, GLABRA 2, HOMEOBOX PROTEIN GLABRA 2
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Disease relevance of GL2


High impact information on GL2

  • Analysis in combination with other root hair mutations showed that CPC may work together with the TTG gene and upstream of the GL2 gene [2].
  • Our molecular and genetic data with double mutants, together with the expression analysis of a GL2 promoter-GUS reporter gene construct, indicate that the RHL1 gene acts independently of GL2 [3].
  • The T-DNA insert in one of the mutant lines cosegregated with the recessive gl2 phenotype and thus served as a molecular tag to isolate genomic DNA at the putative GL2 locus [4].
  • The construction of a full-length cDNA by RT-PCR confirmed the presence of a homeo box in the GL2 gene and showed that it is substantially different from other recently cloned homeo box genes in plants [4].
  • RFLP analysis of the segregating population and subsequent molecular complementation experiments established that the GL2 gene had been cloned [4].

Biological context of GL2

  • The results of in situ nucleic acid hybridization and GUS reporter gene fusion studies show that the GL2 gene is preferentially expressed in the differentiating hairless cells of the wild type, during a period in which epidermal cell identity is believed to be established [5].
  • In support of this hypothesis, it was found that ectopic expression of GL1 in the presence of ectopic expression of the maize R gene, which can bypass the requirement for TTG, can ectopically activate GL2 transcription [6].
  • Using in situ RNA hybridization and a sensitive GL2::GFP reporter, we discovered that a position-dependent pattern of GL2 expression is established within protodermal cells at the heart stage and is maintained throughout the remainder of embryogenesis [7].
  • The GLABRA2 (GL2) gene is required for subsequent phases of trichome morphogenesis such as cell expansion, branching, and maturation of the trichome cell wall [6].
  • A position-dependent pattern of cell differentiation and GL2-promoter activity was also discovered in the hypocotyl epidermis that was analogous to the pattern in the root [8].

Anatomical context of GL2

  • The expression pattern of GL2, as demonstrated by in situ hybridization, indicated that the gene is expressed in trichome progenitor cells and at stages associated with trichome development [4].
  • In the root epidermis of Arabidopsis, cells differentiate in alternating files of hair cells and non-hair cells, in response to positional information and the activity of the homoeodomain transcription factor GLABRA2 (GL2) in future non-hair cells [9].

Associations of GL2 with chemical compounds

  • A model is proposed in which the patterning of root epidermal cells in Arabidopsis is regulated by the cell position-dependent action of the TTG/GL2 pathway, and the ethylene and auxin hormone pathways act to promote root hair outgrowth at a relatively late stage of differentiation [10].

Regulatory relationships of GL2

  • Here, we show that CPC is also predominantly expressed in the hairless cells, but not in the neighboring hair-forming cells, and that CPC protein moves to the hair-forming cells and represses the GL2 expression [11].
  • In the embryonic hypocotyl we show that WER controls GL2 expression [12].

Other interactions of GL2

  • We have examined the genetic relationship between RHL1 and GL2, an inhibitor of root hair initiation in non-hair cells [3].
  • GL2, like GL1, is expressed in developing trichomes and in cells surrounding trichomes during early stages of trichome development [6].
  • These findings, together with the results from our yeast two-hybrid analysis, suggest that GL3 gene function and overexpression of AtmybL2 act synergistically to inhibit trichome formation by negatively regulating GL2 expression [13].
  • The expression of GL2 at the heart stage requires WER function [12].
  • Previous studies have shown that GL2 is a member of the homeodomain class of transcription factors [6].

Analytical, diagnostic and therapeutic context of GL2


  1. Entopically additive expression of GLABRA2 alters the frequency and spacing of trichome initiation. Ohashi, Y., Oka, A., Ruberti, I., Morelli, G., Aoyama, T. Plant J. (2002) [Pubmed]
  2. Epidermal cell differentiation in Arabidopsis determined by a Myb homolog, CPC. Wada, T., Tachibana, T., Shimura, Y., Okada, K. Science (1997) [Pubmed]
  3. The ROOT HAIRLESS 1 gene encodes a nuclear protein required for root hair initiation in Arabidopsis. Schneider, K., Mathur, J., Boudonck, K., Wells, B., Dolan, L., Roberts, K. Genes Dev. (1998) [Pubmed]
  4. The GLABRA2 gene encodes a homeo domain protein required for normal trichome development in Arabidopsis. Rerie, W.G., Feldmann, K.A., Marks, M.D. Genes Dev. (1994) [Pubmed]
  5. The homeobox gene GLABRA2 is required for position-dependent cell differentiation in the root epidermis of Arabidopsis thaliana. Masucci, J.D., Rerie, W.G., Foreman, D.R., Zhang, M., Galway, M.E., Marks, M.D., Schiefelbein, J.W. Development (1996) [Pubmed]
  6. Control of GL2 expression in Arabidopsis leaves and trichomes. Szymanski, D.B., Jilk, R.A., Pollock, S.M., Marks, M.D. Development (1998) [Pubmed]
  7. Embryonic control of epidermal cell patterning in the root and hypocotyl of Arabidopsis. Lin, Y., Schiefelbein, J. Development (2001) [Pubmed]
  8. A common position-dependent mechanism controls cell-type patterning and GLABRA2 regulation in the root and hypocotyl epidermis of Arabidopsis. Hung, C.Y., Lin, Y., Zhang, M., Pollock, S., Marks, M.D., Schiefelbein, J. Plant Physiol. (1998) [Pubmed]
  9. Chromatin organization and cell fate switch respond to positional information in Arabidopsis. Costa, S., Shaw, P. Nature (2006) [Pubmed]
  10. Hormones act downstream of TTG and GL2 to promote root hair outgrowth during epidermis development in the Arabidopsis root. Masucci, J.D., Schiefelbein, J.W. Plant Cell (1996) [Pubmed]
  11. Role of a positive regulator of root hair development, CAPRICE, in Arabidopsis root epidermal cell differentiation. Wada, T., Kurata, T., Tominaga, R., Koshino-Kimura, Y., Tachibana, T., Goto, K., Marks, M.D., Shimura, Y., Okada, K. Development (2002) [Pubmed]
  12. Epidermal patterning genes are active during embryogenesis in Arabidopsis. Costa, S., Dolan, L. Development (2003) [Pubmed]
  13. Overexpression of the AtmybL2 gene represses trichome development in Arabidopsis. Sawa, S. DNA Res. (2002) [Pubmed]
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