Functional Complementation Studies and Analysis of Downstream Regulatory Gene Expression Networks of Trichome Trimeric Complex

  • Anh Phu Nam Bui Division of Biotechnology, Institute of Agricultural Sciences for Southern Vietnam, 121 Nguyen-Binh-Khiem Street, District 01, Ho Chi Minh city 71007, Vietnam, Department of Cell Biology, Texas Tech University Health Sciences Center, 3601 4th street, Lubbock, Texas 79430, USA
  • Vimal Kumar Balasubramanian Pacific Northwest National Laboratory, 902 Battelle Blvd, Richland, WA 99354, USA
  • Thuan-Anh Nguyen-Huu Faculty of Biotechnology, Nguyen Tat Thanh University, 298A-300A Nguyen Tat Thanh Street, Ward 13, District 4, Ho Chi Minh city 72820, Vietnam
  • Tuan-Loc Le Faculty of Biotechnology, Nguyen Tat Thanh University, 298A-300A Nguyen Tat Thanh Street, Ward 13, District 4, Ho Chi Minh city 72820, Vietnam
  • Hoang Dung Tran Faculty of Biotechnology, Nguyen Tat Thanh University, 298A-300A Nguyen Tat Thanh Street, Ward 13, District 4, Ho Chi Minh city 72820, Vietnam
Keywords: Arabidopsis, trichome, MYB2, TTG3, DEL65, DEL61, A genome, D genomes


In Arabidopsis, previous genetic analysis has revealed that trichome initiation is positively mediated by a trimeric activation complex comprised of an R2R3-MYB protein GLABRA1 (GL1), a basic helix-loop-helix (bHLH) GLABRA3 (GL3) which acts redundantly with its close homolog ENHANCER OF GLABRA3 (EGL3), and a WD40 protein TRANSPARENT TESTA GLABRA1 (TTG1). We studied the functionality of four individual cotton genes MYB2, TTG3, DEL65 and DEL61 from diploid cotton A and D genomes, which show high similarity in sequence with GL1, TTG1, GL3 and EGL3, respectively, in their respective Arabidopsis glabrous mutants. Our complementation assays proved that transgenic lines with MYB2, TTG3 from diploid genomes A and D could rescue the trichomeless phenotype of gl1-1 and ttg1-1, respectively. However, DEL61 from both the species could not rescue this phenotype of gl3-1 egl3-77439 double mutant. Interestingly, the DEL65 from A species rescued gl3-1 egl3-77439 double mutant but not from D diploid species. Comparative quantitative PCR analysis of the downstream regulatory network genes showed a similar pattern for MYB, TTG3 complemented lines from A- and D- diploid species. Comparative analysis of the DEL65 from A- (rescued the trichomeless phenotype) and D- (did not rescued the trichomeless phenotype) showed differential expression of regulatory network genes between these two lines. These results suggested that MYB2, TTG3 and DEL65, when expressed in Arabidopsis, regulated the regulatory network genes during the trichome initiation process.


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