title: The conserved chimeric transcript UPGRADE2 is associated with unreduced pollen formation and is exclusively found in apomictic Boechera species.
abstract: In apomictic Boechera spp., meiotic diplospory leads to the circumvention of meiosis and the suppression of recombination to produce unreduced male and female gametes (i.e. apomeiosis). Here, we have established an early flower developmental staging system and have performed microarray-based comparative gene expression analyses of the pollen mother cell stage in seven diploid sexual and seven diploid apomictic genotypes to identify candidate factors for unreduced pollen formation. We identified a transcript unique to apomictic Boechera spp. called UPGRADE2 (BspUPG2), which is highly up-regulated in their pollen mother cells. BspUPG2 is highly conserved among apomictic Boechera spp. genotypes but has no homolog in sexual Boechera spp. or in any other taxa. BspUPG2 undergoes posttranscriptional processing but lacks a prominent open reading frame. Together with the potential of stably forming microRNA-like secondary structures, we hypothesize that BspUPG2 functions as a long regulatory noncoding messenger RNA-like RNA. BspUPG2 has apparently arisen through a three-step process initiated by ancestral gene duplication of the original BspUPG1 locus, followed by sequential insertions of segmentally duplicated gene fragments, with final exonization of its sequence structure. Its genesis reflects the hybridization history that characterizes the genus Boechera.
authors.affiliation: Leibniz Institute of Plant Genetics and Crop Plant Research, D-06466 Gatersleben, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Mau
authors.forename: José M
authors.initials: JM
authors.lastname: Corral
authors.forename: Heiko
authors.initials: H
authors.lastname: Vogel
authors.forename: Michael
authors.initials: M
authors.lastname: Melzer
authors.forename: Jörg
authors.initials: J
authors.lastname: Fuchs
authors.forename: Markus
authors.initials: M
authors.lastname: Kuhlmann
authors.forename: Nico
authors.initials: N
authors.lastname: de Storme
authors.forename: Danny
authors.initials: D
authors.lastname: Geelen
authors.forename: Timothy F
authors.initials: TF
authors.lastname: Sharbel
mesh_terms: D000595:Amino Acid Sequence; D060832:Apomixis / Q000235:genetics*; D019607:Brassicaceae / Q000166:cytology / Q000235:genetics* / Q000254:growth & development*; D002678:Chimera; D032461:Chromosomes, Plant / Q000378:metabolism; D017124:Conserved Sequence; D035264:Flowers / Q000033:anatomy & histology / Q000166:cytology; D020440:Gene Duplication; D018506:Gene Expression Regulation, Plant; D015321:Gene Rearrangement / Q000235:genetics; D017343:Genes, Plant / Q000235:genetics; D008540:Meiosis; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D011058:Pollen / Q000166:cytology / Q000235:genetics* / Q000254:growth & development*; D014176:Protein Biosynthesis / Q000235:genetics; D017510:Protein Folding; D017433:Protein Structure, Secondary; D012326:RNA Splicing / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013045:Species Specificity; D014158:Transcription, Genetic
chemical_list: D010940:Plant Proteins; D012333:RNA, Messenger