Mutations in the predicted DNA polymerase subunit POLD3 result in more rapid flowering of brachypodium distachyon

Authors: WOODS, DANIEL - University Of Wisconsin; DONG, YINXIN - University Of Wisconsin; BOUCHE, FREDERIC - University Of Wisconsin; MAYER, KEVIN - University Of Wisconsin; VARNER, LEAH - University Of Wisconsin; REAM, THOMAS - University Of Wisconsin; THROWER, NICHOLAS - University Of Wisconsin; WILKERSON, CURTIS - University Of Wisconsin; CARTWRIGHT, AMY - Department Of Energy Joint Genome; SIBOUT, RICHARD - Institut National De La Recherche Agronomique (INRA); L Chingcuanco, Debbie; VOGEL, JOHN - Department Of Energy Joint Genome; AMASINO, RICHARD - University Of Wisconsin

Submitted to: New Phytologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/18/2020
Publication Date: 3/15/2020
Citation: Woods, D., Dong, Y., Bouche, F., Mayer, K., Varner, L., Ream, T., Thrower, N., Wilkerson, C., Cartwright, A., Sibout, R., Chingcuanco, D.L., Vogel, J., Amasino, R. 2020. Mutations in the predicted DNA polymerase subunit POLD3 result in more rapid flowering of brachypodium distachyon. New Phytologist. 227:1725-1735. https://doi.org/10.1111/nph.16546.
DOI: https://doi.org/10.1111/nph.16546

Interpretive Summary: In this study we performed a forward genetic screen to isolate mutants that affect the timing of Brachypodium flowering and discovered that lesions in the gene encoding POLD3 subunit of DNA polymerase delta result in more rapid flowering. This study is the first report of the consequences of mutations in the POLD3 gene in plants, and the first report of the consequences of mutations in any DNA polymerase delta subunits in monocots. We provide a characterization of the developmental and gene expression phenotypes that result from a lesion in POLD3, and we compare and contrast our results with other published reports of the consequences of lesions in other subunits of DNA polymerase delta and DNA polymerase epsilon and alpha in both plants and animals.

Technical Abstract: The timing of reproduction is a critical developmental decision in the life cycle of many plant species. To better understand the mechanism of flowering time in plants, we performed a forward genetic screen to isolate mutants that affect the time to flower in Brachypodium. Fine mapping of a rapid-flowering mutant identified was done using whole-genome sequence data from bulked DNA from a segregating F2 mapping population. The causative mutation mapped to a gene orthologous with the third subunit of DNA polymerase d (POLD3), a previously uncharacterized gene in plants. Expression analyses of POLD3 were conducted via real time qPCR to determine when and in what tissues the gene is expressed. Transcriptomic analyses conducted in the mutant versus wild type identified a range of genes involved in floral induction and flower development that were upregulated in the mutant. Our results provide the first characterization of the developmental and gene expression phenotypes that result from a lesion in POLD3 in plants.