VAN4 encodes a putative TRS120 that is required for normal cell growth and vein development in Arabidopsis.
Leaf venation develops complex patterns in angiosperms, but the mechanism underlying this process is largely unknown. To elucidate the molecular mechanisms governing vein pattern formation, we previously isolated vascular network defective (van) mutants that displayed venation discontinuities. Here, we report the phenotypic analysis of van4 mutants, and we identify and characterize the VAN4 gene. Detailed phenotypic analysis shows that van4 mutants are defective in procambium cell differentiation and subsequent vascular cell differentiation. Reduced shoot and root cell growth is observed in van4 mutants, suggesting that VAN4 function is important for cell growth and the establishment of venation continuity. Consistent with these phenotypes, the VAN4 gene is strongly expressed in vascular and meristematic cells. VAN4 encodes a putative TRS120, which is a known guanine nucleotide exchange factor (GEF) for Rab GTPase involved in regulating vesicle transport, and a known tethering factor that determines the specificity of membrane fusion. VAN4 protein localizes at the trans-Golgi network/early endosome (TGN/EE). Aberrant recycling of the auxin efflux carrier PIN proteins is observed in van4 mutants. These results suggest that VAN4-mediated exocytosis at the TGN plays important roles in plant vascular development and cell growth in shoot and root. Our identification of VAN4 as a putative TRS120 shows that Rab GTPases are crucial (in addition to ARF GTPases) for continuous vascular development, and provides further evidence for the importance of vesicle transport in leaf vascular formation.
Department of Biological Sciences, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033 Japan.
Satoshi
S
Naramoto
Tomasz
T
Nodzyłski
Tomoko
T
Dainobu
Hirotomo
H
Takatsuka
Teruyo
T
Okada
Jiři
J
Friml
Hiroo
H
Fukuda
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000033:anatomy & histology / Q000166:cytology* / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D049109:Cell Proliferation; D003001:Cloning, Molecular; D018548:Cotyledon / Q000378:metabolism; D005089:Exocytosis; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D008565:Membrane Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D058526:Plant Vascular Bundle / Q000254:growth & development* / Q000378:metabolism; D021381:Protein Transport; D013347:Subcellular Fractions / Q000378:metabolism
D029681:Arabidopsis Proteins; D018797:Cell Cycle Proteins; D008565:Membrane Proteins; C586781:TRS120 protein, Arabidopsis
Arabidopsis; Cell growth; Guanine nucleotide exchange factor (GEF); Leaf venation pattern; Vascular cell differentiation; Vesicle trafficking