Successful male gametogenesis involves orchestration of sequential gene regulation for somatic differentiation in pre-meiotic anthers. We report here the cloning of Male Sterile23 (Ms23), encoding an anther-specific predicted basic helix-loop-helix (bHLH) transcription factor required for tapetal differentiation; transcripts localize initially to the precursor secondary parietal cells then predominantly to daughter tapetal cells. In knockout ms23-ref mutant anthers, five instead of the normal four wall layers are observed. Microarray transcript profiling demonstrates a more severe developmental disruption in ms23-ref than in ms32 anthers, which possess a different bHLH defect. RNA-seq and proteomics data together with yeast two-hybrid assays suggest that MS23 along with MS32, bHLH122 and bHLH51 act sequentially as either homo- or heterodimers to choreograph tapetal development. Among them, MS23 is the earliest-acting factor, upstream of bHLH51 and bHLH122, controlling tapetal specification and maturation. By contrast, MS32 is constitutive and independently regulated and is required later than MS23 in tapetal differentiation.
The authors declare no competing or financial interests.
G.-L.N. and V.W. conceived and designed the experiments; G.-L.N. conducted the research; J.Z. analyzed the RNA-seq data; S.A. generated the RNA-seq libraries; D.M., L.M. and N.N. performed the microarray experiments; J.F. analyzed the array data; G.-L.N., B.C.M. and V.W. wrote the manuscript; all authors read and approved the manuscript.
This work was supported by a National Science Foundation IOS award (#1339229).
Microarray and RNA-seq data have been deposited in http://www.ncbi.nlm.gov/geo under accession numbers GSE90968 and GSE90849, respectively.
Supplementary information available online at http://dev.biologists.org/lookup/doi/10.1242/dev.140673.supplemental
- Received June 1, 2016.
- Accepted November 21, 2016.