Dimerization in LBD16 and LBD18 Transcription Factors Is Critical for Lateral Root Formation.
LATERAL ORGAN BOUNDARIES DOMAIN/ASYMMETRIC LEAVES2-LIKEs (hereafter referred to as LBD) are plant-specific transcription factors that play important roles in a plethora of plant growth and development. The leucine (Leu) zipper-like coiled-coil motif in the lateral organ boundaries domain of the class I LBD proteins has been proposed to mediate protein dimerization, but it has not been experimentally assessed yet. LBD16 and LBD18 have been well characterized to play important roles in lateral root development in Arabidopsis (Arabidopsis thaliana). Here, we investigated the role of the coiled-coil motif in the dimerization of LBD16 and LBD18 and in transcriptional regulation and biological function. We built the molecular models of the coiled coil of LBD16 and LBD18, providing the probable Leu zipper models of the helix dimer. Using a variety of molecular techniques, such as bimolecular fluorescence complementation, luciferase complementation imaging, GST pull down, and coimmunoprecipitation assays, we showed that the conserved Leu or valine residues in the coiled-coil motif are critical for the dimerization of LBD16 or LBD18. Using transgenic Arabidopsis plants that overexpress HA:LBD16 or HA:LBD16Qinlbd16or HA:LBD18 or HA:LBD18Qinlbd18, we demonstrated that the homodimerization of LBD18 mediated by the coiled-coil motif is crucial for transcriptional regulation via promoter binding and for lateral root formation. In addition, we found that the carboxyl-terminal region beyond the coiled-coil motif in LBD18 acts as an additional dimerization domain. These results provide a molecular basis for homodimerization and heterodimerization among the 42 Arabidopsis LBD family members for displaying their biological functions.
Department of Bioenergy Science and Technology (H.W.L., N.Y.K., S.K.P., C.C., J.K.) and Kumho Life Science Laboratory (J.K.), Chonnam National University, Gwangju 500-757, Korea; and.|Department of Cellular and Molecular Medicine, Chosun University School of Medicine, Gwangju 501-759, Korea (S.H.L.).
Han Woo
HW
Lee
Department of Bioenergy Science and Technology (H.W.L., N.Y.K., S.K.P., C.C., J.K.) and Kumho Life Science Laboratory (J.K.), Chonnam National University, Gwangju 500-757, Korea; and.|Department of Cellular and Molecular Medicine, Chosun University School of Medicine, Gwangju 501-759, Korea (S.H.L.).
Na Young
NY
Kang
Department of Bioenergy Science and Technology (H.W.L., N.Y.K., S.K.P., C.C., J.K.) and Kumho Life Science Laboratory (J.K.), Chonnam National University, Gwangju 500-757, Korea; and.|Department of Cellular and Molecular Medicine, Chosun University School of Medicine, Gwangju 501-759, Korea (S.H.L.).
Shashank K
SK
Pandey
Department of Bioenergy Science and Technology (H.W.L., N.Y.K., S.K.P., C.C., J.K.) and Kumho Life Science Laboratory (J.K.), Chonnam National University, Gwangju 500-757, Korea; and.|Department of Cellular and Molecular Medicine, Chosun University School of Medicine, Gwangju 501-759, Korea (S.H.L.).
Chuloh
http://orcid.org/0000-0001-7997-1544
C
Cho
Department of Bioenergy Science and Technology (H.W.L., N.Y.K., S.K.P., C.C., J.K.) and Kumho Life Science Laboratory (J.K.), Chonnam National University, Gwangju 500-757, Korea; and.|Department of Cellular and Molecular Medicine, Chosun University School of Medicine, Gwangju 501-759, Korea (S.H.L.).
Sung Haeng
http://orcid.org/0000-0002-6658-9714
SH
Lee
Department of Bioenergy Science and Technology (H.W.L., N.Y.K., S.K.P., C.C., J.K.) and Kumho Life Science Laboratory (J.K.), Chonnam National University, Gwangju 500-757, Korea; and jungmkim@jnu.ac.kr.|Department of Cellular and Molecular Medicine, Chosun University School of Medicine, Gwangju 501-759, Korea (S.H.L.) jungmkim@jnu.ac.kr.
Jungmook
http://orcid.org/0000-0003-1735-5564
J
Kim
D017360:Arabidopsis / Q000166:cytology / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D001665:Binding Sites / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D008958:Models, Molecular; D009154:Mutation; D018517:Plant Roots / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified; D011487:Protein Conformation; D055503:Protein Multimerization; D011523:Protoplasts / Q000378:metabolism; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
D029681:Arabidopsis Proteins; C571893:LBD16 protein, Arabidopsis; C573049:LBD18 protein, Arabidopsis; D014157:Transcription Factors