title: RUPTURED POLLEN GRAIN1, a member of the MtN3/saliva gene family, is crucial for exine pattern formation and cell integrity of microspores in Arabidopsis.
abstract: During microsporogenesis, the microsporocyte (or microspore) plasma membrane plays multiple roles in pollen wall development, including callose secretion, primexine deposition, and exine pattern determination. However, plasma membrane proteins that participate in these processes are still not well known. Here, we report that a new gene, RUPTURED POLLEN GRAIN1 (RPG1), encodes a plasma membrane protein and is required for exine pattern formation of microspores in Arabidopsis (Arabidopsis thaliana). The rpg1 mutant exhibits severely reduced male fertility with an otherwise normal phenotype, which is largely due to the postmeiotic abortion of microspores. Scanning electron microscopy examination showed that exine pattern formation in the mutant is impaired, as sporopollenin is randomly deposited on the pollen surface. Transmission electron microscopy examination further revealed that the primexine formation of mutant microspores is aberrant at the tetrad stage, which leads to defective sporopollenin deposition on microspores and the locule wall. In addition, microspore rupture and cytoplasmic leakage were evident in the rpg1 mutant, which indicates impaired cell integrity of the mutant microspores. RPG1 encodes an MtN3/saliva family protein that is integral to the plasma membrane. In situ hybridization analysis revealed that RPG1 is strongly expressed in microsporocyte (or microspores) and tapetum during male meiosis. The possible role of RPG1 in microsporogenesis is discussed.
authors.affiliation: National Key Laboratory of Plant Molecular Genetics, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200032, China.
authors.forename: Yue-Feng
authors.initials: YF
authors.lastname: Guan
authors.forename: Xue-Yong
authors.initials: XY
authors.lastname: Huang
authors.forename: Jun
authors.initials: J
authors.lastname: Zhu
authors.forename: Ju-Fang
authors.initials: JF
authors.lastname: Gao
authors.forename: Hong-Xia
authors.initials: HX
authors.lastname: Zhang
authors.forename: Zhong-Nan
authors.initials: ZN
authors.lastname: Yang
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000254:growth & development*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D001483:Base Sequence; D017931:DNA Primers; D008855:Microscopy, Electron, Scanning; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D016133:Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid
chemical_list: D029681:Arabidopsis Proteins; D017931:DNA Primers; D009004:Monosaccharide Transport Proteins; C585408:RPG1 protein, Arabidopsis