John C. Larkin

William Lee Professor

BMB and CDIB Divisions

PhD: Carnegie-Mellon University, 1985

Phone: 225-578-8552
Lab Phone: 225-578-8553
Office: 316 Life Sciences Building
Lab: 310/314 Life Sciences Building
E-mail: jlarkin@lsu.edu 

Dr. Larkin is not currently taking new graduate students or postdocs at this time.

Area of Interest

Our lab studies the coordination of the cell division cycle and development during plant development. This coordination crucial to the proper development and functioning of multicellular organisms. In animals, loss of control of cell division leads to cancer. In some cell types, a modified cell cycle occurs during differentiation in which the DNA is replicated without concomitant cell division, resulting in an increase in nuclear DNA content. This process is called endoreplication or endoreduplication. Endoreplication occurs in many cell types important for agriculture or human health: platelet-producing megakaryocytes and placental trophoblast cells in mammals, and cereal endosperm and cotton fibers in plants are all endoreplicated cell types. Endoreplication in nitrogen-fixing root nodules of legumes is essential for symbiotic nitrogen fixation, and recent work indicates that endoreplication stabilizes the commitment to differentiated cell fate. Endoreplication also occurs in response to environmental stresses such as salt stress and DNA damage. 

The switch from a mitotic cell cycle to an endoreplication cell cycle requires suppression of mitotic cyclin-dependent kinase activity. Using the plant genetic model Arabidopsis thaliana discovered a new family of plant-specific cyclin-dependent kinase inhibitors, the SIAMESE-RELATED (SMR) family, that function to suppress mitosis and promote endoreplication. More recent work suggests that SMRs also play a role in controlling the length of the G2 phase of plant cell cycles in addition to promoting endoreplication.  We are using a combination of mathematical modeling of the cell cycle and experimental manipulation using live cell imaging to test this hypothesis. 

SMRs are found in the genomes of all land plants, where they play diverse roles in regulating the cell cycle during plant development and responses to environmental stresses. Our recent work is focusing on the roles of SMRs and the cell cycle during leaf and root development.  In this work, we are comparing development in the well-known model plant A. thaliana to that of Schrenkiella parvula, a species closely related to A. thaliana that is adapted to tolerate extremely saline soils.  Leaves of S. parvula undergo increased endoreplication when grown on high salt. S. parvula leaves also differ significantly in shape from A. thaliana leaves.  We are using anatomical, transcriptomic and transgenic approaches to understand the differences in leaf development of these two species. 

Selected Publications

Tran, K.-N., Pantha, P., Wang, G., Kumar, N., Wijesinghege, C., Oh, D.-H., Duppen, N., Li, H., Hong, H., Johnson, J., Kelt, R., Matherne, M., Clement, A., Tran, D., Crain, C., Adhikari, P.. Zhang, Y., Foroozani, M., Sessa, G., Larkin, J.C., Smith, A., Longstreth, D., Finnegan, P., Testerink, C., Barak, S., and Dassanayake, M. “Balancing growth amidst salt stress - lifestyle perspectives from the extremophyte model Schrenkiella parvula.”  Submitted to Plant Physiology, September 2021. 

Wang, K., Ndathe, R., Kumar, N., Zeringue, E.A., Kato, N., Larkin, J.C. “SIAMESE targets both CDKA;1 and CDKB1 complexes to establish endoreplication in Arabidopsis thaliana trichomes.” 2020. Plant Physiology. https://doi.org/10.1104/pp.20.00271. 

Kumar, N., Dale, R., Kemboi, D., Zeringue, E.A., Kato, N., Larkin, J.C. 2018. “Functional Analysis of Short Linear Motifs in the Plant Cyclin-Dependent Kinase Inhibitor SIAMESE.” Plant Physiol., https://doi.org/10.1104/pp.18.00147. Cover Article. 

Barkla, B.J., Rhodes, T., Tran, K.-N.T., Wijesinghege, C., Larkin, J.C., Dassanayake, M. 2018. “Making Epidermal Bladder Cells Bigger: Developmental- and Salinity-Induced Endopolyploidy in a Model Halophyte.” Plant Physiol., https://doi.org/10.1104/pp.18.00033. 

Hervieux, N., Tsugawa, S., Fruleux, A., Dumond, M., Routier-Kierzkowska, A.-L., Komatsuzaki, T., Boudaoud, A., Larkin, J.C., Smith, R.S., Li, C.-B., Hamant, O. 2017. “Mechanical Shielding of Rapidly Growing Cells Buffers Growth Heterogeneity and Contributes to Organ Shape Reproducibility.” Current Biology, https://doi.org/10.1016/j.cub.2017.10.033 

Dassanayake, M., Larkin, J.C.2017. “Making Plants Break a Sweat: the Structure, Function, and Evolution of Plant Salt Glands.” Frontiers in Plant Biology, doi: 10.3389/fpls.2017.00406. 

Kumar, N., Larkin, J.C. 2017. “Why Do Plants Need So Many Cyclin-Dependent Kinase Inhibitors?” Plant Signaling and Behavior, http://dx.doi.org/10.1080/15592324.2017.1282021 

Kumar, N., Harashima, H, Kalve, S., Bramsiepe, J., Wang, K., Sizani, B.L., Bertrand, L.L., Johnson, M.C., Faulk, C., Dale, R. Simmons, L.A., Churchman, M.L., Sugimoto, K., Kato, N., Dassanayake, M., Beemster, G., Schnittger, A., Larkin, J.C. 2015. “Functional Conservation in the SIAMESE-RELATED Family of Cyclin-Dependent Kinase Inhibitors in Land Plants.” Plant Cell doi: 10.1105/tpc.15.00489 

De Veylder, L., Larkin, J.C. and Schnittger, A. 2011. “Endoreplication in Plant Physiology and Development.” Trends Plant Sci. 16:624-634. 

Churchman M.L., Brown M.L., Kato N., Kirik V., Hulskamp M., Inze D., De Veylder L., Walker J.D., Zheng Z., Oppenheimer D.G., Gwin T., Churchman J., and Larkin J. C. 2006. “SIAMESE, a Plant-Specific Cell Cycle Regulator, Controls Endoreplication Onset in Arabidopsis thaliana.” Plant Cell 18: 3145-3157.