Thomas P. Jack, Ph.D.
78 College Street
Life Sciences Center, 331
Hanover, NH 03755
The long-term goal of the lab is to understand the molecular mechanisms that underlie the development of plants. The plant we study is the model plant Arabidopsis thaliana. In particular, we study the development of the Arabidopsis flower, which like most angiosperm flowers, consists of four organ types: sepals, petals, stamens, and carpels. We are interested in understanding the specification of organ identity and organ growth in flowers. The two floral organ identity genes APETALA3 (AP3) and PISTILLATA (PI) specify petal and stamen development. In ap3 and pi mutants, the petals are converted into sepals, and the stamens into carpels. AP3 and PI are members of the MADS transcription factor family. We carried out two genetic screens to identify additional components that control growth of petals and stamens. One gene of interest that came from these screens is DORNRÖSCHEN-LIKE (DRNL), which encodes an AP2 domain transcription factor. In drnl-2 mutants, stamens most often do not form. A second gene of interest is miR319a, which encodes micro RNA319a. In miR319a mutants, the petals are narrow and stamen filaments are short.
Current Research Projects
Experiments on DRNL focus in two areas. First, several lines of evidence suggest that none of the three extant drnl alleles are null alleles. One potential thesis project is to make a null allele of drnl by using CRISPR/Cas technology and/or inducible RNAi approaches. Once the null allele is in hand, the phenotype needs to be carefully characterized in the embryo and flower. Second, recent evidence suggests that DRNL is expressed very early in flower development, in the founder cells for the floral organs. Using live imaging on a laser scanning confocal microscope, we will determine the spatial and temporal dynamics of DRNL expression compared to auxin (using DR5:GUS) and an auxin transporter PIN1. These experiments will sort out whether DRNL is setting up the auxin gradient in the floral primordia or responding to it.
We are also interested in the function of the SUPERMAN (SUP) gene that is critical for specifying the boundaries between the floral organs. In sup mutants, supernumerary stamens develop at the expense of carpels. This phenotype is associated with an expansion of the expression domain of the two B class genes AP3 and PI towards the center of the flower. However, the large number of stamens that develop in sup mutants (often more than 15) suggests that the sup phenotype does not result solely from a classic homeotic transformation of fourth whorl carpels to stamens; sup mutant flowers also exhibit excessive cell proliferation compared to the wild type. SUP encodes a C2-H2 type zinc finger protein with an EAR domain, thus SUP likely functions as a transcriptional repressor. SUP RNA accumulates at a low level and in a small number of cells in whorl 3 adjacent to the whorl 3/whorl 4 boundary. The project is to elucidate the gene regulatory network controlled by SUP, as well as to identify the specific targets of the SUP transcriptional repressor. This will involve carrying out RNA-seq and ChIP-seq experiments.
Prunet, N., Jack, T. P., and Meyerowitz, E. M. (2016) Live confocal imaging of Arabidopsis flower buds. Dev Biol. 2016 Mar 15. pii: S0012-1606(16)30066-5. doi: 10.1016/j.ydbio.2016.03.018. [Epub ahead of print]
Prunet, N., Morel, P., Champelovier, P., Thierry, A.-M., Negrutiu, I., Jack, T., and Trehin, C. (2015). SQUINT promotes stem cell homeostasis and floral meristem termination in Arabidopsis through APETALA2 and CLAVATA signaling. J. Ex. Bot. 66, 6905-6916.
Pape-Lindstrom, P. A., Jack, T., Miller, K. G., Aguirre, K. M., Awong-Taylor, J., Balser, T. C., Awong-Taylor, J., Brancaccio-Taras, L., Marley, K. E., Osgood, M. P., Peteroy-Kelly, M., Romano, S. L. (2015). PULSE pilot certification results. J. Microbiol. Ed. 16, 127-129.
Wellmer, F., Bowman, J. L., Davies, B., Ferrandiz, C., Fletcher J. C., Franks, R. G., Graciet, E., Gregis, V., Ito, T., Jack, T. P., Jiao, Y., Kater, M. M., Ma, H., Meyerowitz, E. M., Prunet, N., and Riechmann, J. L. (2014). Flower Development: Open Questions and Future Directions. In Methods in Molecular Biology – Flower Development: Methods and Protocols (F. Wellmer and J.-L. Riechmann editors), 103-124.
Prunet, N. and Jack, T. (2014). Flower development in Arabidopsis – there’s more to it than learning your ABCs. In Methods in Molecular Biology – Flower Development: Methods and Protocols (F. Wellmer and J.-L. Riechmann editors), 3-33.
Gauthier, A., and Jack, T. (2014). The Professor and the instructional designer: a course design journey. Transformations: Liberal Arts in the Digital Age.