title: Global transcriptome analysis of two ameiotic1 alleles in maize anthers: defining steps in meiotic entry and progression through prophase I.
abstract: BACKGROUND
  Developmental cues to start meiosis occur late in plants. Ameiotic1 (Am1) encodes a plant-specific nuclear protein (AM1) required for meiotic entry and progression through early prophase I. Pollen mother cells (PMCs) remain mitotic in most am1 mutants including am1-489, while am1-praI permits meiotic entry but PMCs arrest at the leptotene/zygotene (L/Z) transition, defining the roles of AM1 protein in two distinct steps of meiosis. To gain more insights into the roles of AM1 in the transcriptional pre-meiotic and meiotic programs, we report here an in depth analysis of gene expression alterations in carefully staged anthers at 1 mm (meiotic entry) and 1.5 mm (L/Z) caused by each of these am1 alleles.
  
  
  RESULTS
  1.0 mm and 1.5 mm anthers of am1-489 and am1-praI were profiled in comparison to fertile siblings on Agilent® 4 × 44 K microarrays. Both am1-489 and am1-praI anthers are cytologically normal at 1.0 mm and show moderate transcriptome alterations. At the 1.5-mm stage both mutants are aberrant cytologically, and show more drastic transcriptome changes. There are substantially more absolute On/Off and twice as many differentially expressed genes (sterile versus fertile) in am1-489 than in am1-praI. At 1.5 mm a total of 4,418 genes are up- or down-regulated in either am1-489 or am1-praI anthers. These are predominantly stage-specific transcripts. Many putative meiosis-related genes were found among them including a small subset of allele-specific, mis-regulated genes specific to the PMCs. Nearly 60% of transcriptome changes in the set of transcripts mis-regulated in both mutants (N = 530) are enriched in PMCs, and only 1% are enriched in the tapetal cell transcriptome. All array data reported herein will be deposited and accessible at MaizeGDB http://www.maizegdb.org/.
  
  
  CONCLUSIONS
  Our analysis of anther transcriptome modulations by two distinct am1 alleles, am1-489 and am1-praI, redefines the role of AM1 as a modulator of expression of a subset of meiotic genes, important for meiotic progression and provided stage-specific insights into the genetic networks associated with meiotic entry and early prophase I progression.
authors.affiliation: Department of Biology, Stanford University, Stanford, CA 94305, USA. gnan@stanford.edu
authors.forename: Guo-Ling
authors.initials: GL
authors.lastname: Nan
authors.forename: Arnaud
authors.initials: A
authors.lastname: Ronceret
authors.forename: Rachel C
authors.initials: RC
authors.lastname: Wang
authors.forename: John F
authors.initials: JF
authors.lastname: Fernandes
authors.forename: W Zacheus
authors.initials: WZ
authors.lastname: Cande
authors.forename: Virginia
authors.initials: V
authors.lastname: Walbot
mesh_terms: D000483:Alleles; D035264:Flowers / Q000235:genetics / Q000254:growth & development; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D008540:Meiosis; D049469:Meiotic Prophase I; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D051479:Plant Infertility; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D011058:Pollen / Q000235:genetics / Q000254:growth & development*; D018749:RNA, Plant / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D059467:Transcriptome; D003313:Zea mays / Q000235:genetics* / Q000254:growth & development
chemical_list: D010940:Plant Proteins; D018749:RNA, Plant