title: Maize ROP2 GTPase provides a competitive advantage to the male gametophyte.
abstract: Rop GTPases have been implicated in the regulation of plant signal transduction and cell morphogenesis. To explore ROP2 function in maize, we isolated five Mutator transposon insertions (rop2::Mu alleles). Transmission frequency through the male gametophyte, but not the female, was lower than expected in three of the rop2::Mu mutants. These three alleles formed an allelic series on the basis of the relative transmission rate of each when crossed as trans-heterozygotes. A dramatic reduction in the level of ROP2-mRNA in pollen was associated with the three alleles causing a transmission defect, whereas a rop2::Mu allele that did not result in a defect had wild-type transcript levels, thus confirming that mutation of rop2 causes the mutant phenotype. These data strongly support a role for rop2 in male gametophyte function, perhaps surprisingly, given the expression in pollen of the nearly identical duplicate gene rop9. However, the transmission defect was apparent only when a rop2::Mu heterozygote was used as the pollen donor or when a mixture of wild-type and homozygous mutant pollen was used. Thus, mutant pollen is at a competitive disadvantage compared to wild-type pollen, although mutant pollen grains lacked an obvious cellular defect. Our data demonstrate the importance in vivo of a specific Rop, rop2, in the male gametophyte.
authors.affiliation: Center for Gene Research and Biotechnology and Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon 97331, USA.
authors.forename: K M
authors.initials: KM
authors.lastname: Arthur
authors.forename: Z
authors.initials: Z
authors.lastname: Vejlupkova
authors.forename: R B
authors.initials: RB
authors.lastname: Meeley
authors.forename: J E
authors.initials: JE
authors.lastname: Fowler
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D001483:Base Sequence; D004251:DNA Transposable Elements / Q000235:genetics; D006579:Heterozygote; D006720:Homozygote; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics*; D010641:Phenotype; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000254:growth & development; D011058:Pollen / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D003313:Zea mays / Q000201:enzymology / Q000254:growth & development*; D020741:rho GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D004251:DNA Transposable Elements; D012333:RNA, Messenger; D018749:RNA, Plant; D020741:rho GTP-Binding Proteins