Arabidopsis UNHINGED encodes a VPS51 homolog and reveals a role for the GARP complex in leaf shape and vein patterning.
Asymmetric localization of PIN proteins controls directionality of auxin transport and many aspects of plant development. Directionality of PIN1 within the marginal epidermis and the presumptive veins of developing leaf primordia is crucial for establishing leaf vein pattern. One mechanism that controls PIN protein distribution within the cell membranes is endocytosis and subsequent transport to the vacuole for degradation. The Arabidopsis mutant unhinged-1 (unh-1) has simpler leaf venation with distal non-meeting of the secondary veins and fewer higher order veins, a narrower leaf with prominent serrations, and reduced root and shoot growth. We identify UNH as the Arabidopsis vacuolar protein sorting 51 (VPS51) homolog, a member of the Arabidopsis Golgi-associated retrograde protein (GARP) complex, and show that UNH interacts with VPS52, another member of the complex and colocalizes with trans Golgi network and pre-vacuolar complex markers. The GARP complex in yeast and metazoans retrieves vacuolar sorting receptors to the trans-Golgi network and is important in sorting proteins for lysosomal degradation. We show that vacuolar targeting is reduced in unh-1. In the epidermal cells of unh-1 leaf margins, PIN1 expression is expanded. The unh-1 leaf phenotype is partially suppressed by pin1 and cuc2-3 mutations, supporting the idea that the phenotype results from expanded PIN1 expression in the marginal epidermis. Our results suggest that UNH is important for reducing expression of PIN1 within margin cells, possibly by targeting PIN1 to the lytic vacuole.
Department of Biological Sciences, University of Lethbridge, Lethbridge, AB TIK 3M4, Canada.
Shankar
S
Pahari
Ryan D
RD
Cormark
Michael T
MT
Blackshaw
Chen
C
Liu
Jessica L
JL
Erickson
Elizabeth A
EA
Schultz
D000483:Alleles; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D015415:Biomarkers / Q000378:metabolism; D019521:Body Patterning; D003001:Cloning, Molecular; D018548:Cotyledon / Q000033:anatomy & histology; D005816:Genetic Complementation Test; D005838:Genotype; D005966:Glucuronidase / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000378:metabolism; D008954:Models, Biological; D046912:Multiprotein Complexes / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D019441:Plant Epidermis / Q000166:cytology / Q000378:metabolism; D018515:Plant Leaves / Q000033:anatomy & histology*; D018517:Plant Roots / Q000378:metabolism; D018520:Plant Shoots / Q000378:metabolism; D058526:Plant Vascular Bundle / Q000254:growth & development* / Q000378:metabolism; D021381:Protein Transport; D014617:Vacuoles / Q000378:metabolism; D033921:Vesicular Transport Proteins / Q000378:metabolism*; D021601:trans-Golgi Network / Q000378:metabolism
D029681:Arabidopsis Proteins; D015415:Biomarkers; D026901:Membrane Transport Proteins; D046912:Multiprotein Complexes; C116363:PIN1 protein, Arabidopsis; C000588863:UNHINGED protein, Arabidopsis; D033921:Vesicular Transport Proteins; D049452:Green Fluorescent Proteins; D005966:Glucuronidase
GARP; Leaf shape; Leaf vein patterning; PIN1 localization; Retrograde trafficking; VPS51