title: Arabidopsis reversibly glycosylated polypeptides 1 and 2 are essential for pollen development.
abstract: Reversibly glycosylated polypeptides (RGPs) have been implicated in polysaccharide biosynthesis. To date, to our knowledge, no direct evidence exists for the involvement of RGPs in a particular biochemical process. The Arabidopsis (Arabidopsis thaliana) genome contains five RGP genes out of which RGP1 and RGP2 share the highest sequence identity. We characterized the native expression pattern of Arabidopsis RGP1 and RGP2 and used reverse genetics to investigate their respective functions. Although both genes are ubiquitously expressed, the highest levels are observed in actively growing tissues and in mature pollen, in particular. RGPs showed cytoplasmic and transient association with Golgi. In addition, both proteins colocalized in the same compartments and coimmunoprecipitated from plant cell extracts. Single-gene disruptions did not show any obvious morphological defects under greenhouse conditions, whereas the double-insertion mutant could not be recovered. We present evidence that the double mutant is lethal and demonstrate the critical role of RGPs, particularly in pollen development. Detailed analysis demonstrated that mutant pollen development is associated with abnormally enlarged vacuoles and a poorly defined inner cell wall layer, which consequently results in disintegration of the pollen structure during pollen mitosis I. Taken together, our results indicate that RGP1 and RGP2 are required during microspore development and pollen mitosis, either affecting cell division and/or vacuolar integrity.
authors.affiliation: The Center for Plant Cell Biology and Department of Botany and Plant Sciences, University of California, Riverside, California 92521, USA.
authors.forename: Georgia
authors.initials: G
authors.lastname: Drakakaki
authors.forename: Olga
authors.initials: O
authors.lastname: Zabotina
authors.forename: Ivan
authors.initials: I
authors.lastname: Delgado
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Robert
authors.forename: Kenneth
authors.initials: K
authors.lastname: Keegstra
authors.forename: Natasha
authors.initials: N
authors.lastname: Raikhel
mesh_terms: D017360:Arabidopsis / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D003433:Crosses, Genetic; D003593:Cytoplasm / Q000378:metabolism; D005964:Glucosyltransferases / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D006023:Glycoproteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D006056:Golgi Apparatus / Q000378:metabolism; D008938:Mitosis / Q000235:genetics / Q000502:physiology; D005810:Multigene Family; D010802:Phylogeny; D011058:Pollen / Q000033:anatomy & histology / Q000254:growth & development* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000032:analysis
chemical_list: D029681:Arabidopsis Proteins; D006023:Glycoproteins; C106959:RGP1 protein, Arabidopsis; D011993:Recombinant Fusion Proteins; D005964:Glucosyltransferases; C518081:RGP2 protein, Arabidopsis