The founder-cell transcriptome in the Arabidopsis apetala1 cauliflower inflorescence meristem.
Although the pattern of lateral organ formation from apical meristems establishes species-specific plant architecture, the positional information that confers cell fate to cells as they transit to the meristem flanks where they differentiate, remains largely unknown. We have combined fluorescence-activated cell sorting and RNA-seq to characterise the cell-type-specific transcriptome at the earliest developmental time-point of lateral organ formation using DORNRÖSCHEN-LIKE::GFP to mark founder-cell populations at the periphery of the inflorescence meristem (IM) in apetala1 cauliflower double mutants, which overproliferate IMs.



Within the lateral organ founder-cell population at the inflorescence meristem, floral primordium identity genes are upregulated and stem-cell identity markers are downregulated. Additional differentially expressed transcripts are involved in polarity generation and boundary formation, and in epigenetic and post-translational changes. However, only subtle transcriptional reprogramming within the global auxin network was observed.



The transcriptional network of differentially expressed genes supports the hypothesis that lateral organ founder-cell specification involves the creation of polarity from the centre to the periphery of the IM and the establishment of a boundary from surrounding cells, consistent with bract initiation. However, contrary to the established paradigm that sites of auxin response maxima pre-pattern lateral organ initiation in the IM, auxin response might play a minor role in the earliest stages of lateral floral initiation.
Institute of Developmental Biology, University of Cologne, Cologne Biocenter, Zuelpicher Strasse 47b, D-50674, Cologne, Germany.
Anneke
A
Frerichs
Present address: Department of Plant Breeding and Genetics, Max Planck Institute for Plant Breeding Research, Carl-von-Linné-Weg 10, D-50829, Cologne, Germany.
Rahere
R
Thoma
CECAD Research Center, University of Cologne, Joseph-Stelzmann-Str. 26, 50931, Cologne, Germany.
Ali Taleb
AT
Abdallah
CECAD Research Center, University of Cologne, Joseph-Stelzmann-Str. 26, 50931, Cologne, Germany.
Peter
P
Frommolt
Institute of Developmental Biology, University of Cologne, Cologne Biocenter, Zuelpicher Strasse 47b, D-50674, Cologne, Germany.
Wolfgang
W
Werr
Institute of Developmental Biology, University of Cologne, Cologne Biocenter, Zuelpicher Strasse 47b, D-50674, Cologne, Germany. john.chandler@uni-koeln.de.
John William
JW
Chandler
D001937:Brassica / Q000235:genetics*; D016000:Cluster Analysis; D019295:Computational Biology / Q000379:methods; D044127:Epigenesis, Genetic; D015870:Gene Expression; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D063990:Gene Ontology; D053263:Gene Regulatory Networks; D017930:Genes, Reporter; D056626:Inflorescence / Q000235:genetics*; D018519:Meristem / Q000235:genetics*; D010641:Phenotype; D059828:Plant Cells / Q000378:metabolism; D012323:RNA Processing, Post-Transcriptional; D059467:Transcriptome
Bract; DORNRÖSCHEN-LIKE; Fluorescence-activated cell sorting; Inflorescence meristem; Lateral organ founder cell; RNA-seq; Transcriptome; apetala1 cauliflower