Functional specialization within the vacuolar sorting receptor family: VSR1, VSR3 and VSR4 sort vacuolar storage cargo in seeds and vegetative tissues.
Two different gene families have been proposed to act as sorting receptors for vacuolar storage cargo in plants: the vacuolar sorting receptors (VSRs) and the receptor homology-transmembrane-RING H2 domain proteins (RMRs). However, functional data on these genes is scarce and the identity of the sorting receptor for storage proteins remains controversial. Through a genetic screen we have identified the mtv2 mutant, which is defective in vacuolar transport of the storage cargo VAC2 in shoot apices. Map-based cloning revealed that mtv2 is a loss of function allele of the VSR4 gene. We show that VSR1, VSR3 and VSR4, but not the remaining VSRs or RMRs, participate in vacuolar sorting of VAC2 in vegetative tissues, and 12S globulins and 2S albumins in seeds, an activity that is essential for seedling germination vigor. Finally, we demonstrate that the functional diversification in the VSR family results from divergent expression patterns and also from distinct sorting activities of the family members.
Zouhar
Jan
J
Departamento de Genética Molecular de Plantas, Centro Nacional de Biotecnología-CSIC, E-28049 Madrid, Spain.
Muñoz
Alfonso
A
Rojo
Enrique
E
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D018525:Germination; D008565:Membrane Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D005810:Multigene Family; D018515:Plant Leaves / Q000378:metabolism; D018520:Plant Shoots / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D011993:Recombinant Fusion Proteins; D055314:Seed Storage Proteins / Q000378:metabolism*; D012639:Seeds / Q000378:metabolism*; D014617:Vacuoles
C118167:AT2G27250 protein, Arabidopsis; D029681:Arabidopsis Proteins; C106564:ELP protein, Arabidopsis; D008565:Membrane Proteins; C505135:RMR1 protein, Arabidopsis; D018160:Receptors, Cytoplasmic and Nuclear; D011993:Recombinant Fusion Proteins; D055314:Seed Storage Proteins; C529649:VSR3 protein, Arabidopsis