- Sheila McCormick
- Pollen, Plant Fertilization
- Adjunct Professor Emerita
- 111 Koshland Hall
- Berkeley, California 94720-3102
Ph.D. Genetics University of Missouri-Columbia, 1978
B.S. Biology Illinois State University, 1973
We studied plant reproduction using biochemistry, cell biology, genetics and molecular biology, in 3 projects: 1) Pollen tube growth: we characterize signal transduction pathways mediated through pollen-specific receptor kinases; 2) Pollen development and function: we characterize mutations that affect transmission through the male parent; and 3) Gamete biology: we characterize sperm, egg, or embryo sac-expressed genes that may play roles in pollen tube guidance, gamete recognition or fusion.
Molecular Biology of Plant Reproduction
Pollen Tube Growth
We studied pollen-specific receptor kinases and how they perceive and transduce signals for pollen tube growth. We used yeast two hybrid screens to identify potential ligands; these include LAT52 and LeSHY, pollen proteins, and LeSTIG1, a stigma-specific protein. We think that the receptor kinases interact with different ligands during different phases of pollen tube growth. We also used yeast two hybrid screens to identify cytoplasmic partners for these receptor kinases; one partner, called KPP, is a guanine nucleotide exchange factor for Rops. Rops are small GTPases. Thus our work provides a link from receptor kinases to the Rop-mediated cytoplasmic dynamics that are needed for pollen tube growth.
Pollen tubes (stained with decolorized aniline blue) growing through a tomato style.
Pollen development and function
About 10% of the genes in plants are specifically or selectively expressed in pollen, but the functions of most are not understood. We used Arabidopsis to identify mutants that are defective at a stage of pollen development, or during pollen hydration, pollen tube growth, pollen tube guidance, or fertilization. Usually such mutants have altered transmission through the male parent, but do not affect the female.
The giftwrap pollen mutant has what appears to be ribbons tied in bows inside the pollen grain (stained with decolorized aniline blue).
We were interested in double fertilization, specifically in how the two sperm and their fusion partners, the egg and the central cell, recognize and fuse with each other. To develop tools for this objective, we generated cDNA libraries from maize sperm, eggs, and embryo sacs, sequenced ~20,000 ESTs, then used these datasets as starting points to identify gamete-specific genes. We identified promoter elements that will drive gamete-specific gene expression. We then used Arabidopsis to identify T-DNA insertions in gamete-expressed genes, and test whether there is a phenotype. We have evidence that fertilization fails when some of these genes are disrupted.Pollen grains whose sperm cells are expressing GFP from a sperm-specific promoter.
Fun StuffFlat Stanley helping to vacuum pollen from Arabidopsis plants
For pdfs of these and other papers, see the McCormick web site.
Jiang H, Yi J, Boavida LC, Chen Y, Becker JD, Köhler C, McCormick S. 2015. Intercellular communication in pollen discovered via AHG3 transcript movement from the vegetative cell to sperm. Proc Natl Acad Sci USA 112:13378-83. doi: 10.1073/pnas.1510854112
Gui, C., Dong, X., Liu, H., Huang, W., Zhang, D., Wang, S., Barberini, M.L., Gao, X., Muschietti, J., McCormick, S. and Tang, W. 2014. Overexpression of the tomato pollen receptor kinase LePRK1 rewires pollen tube growth to a blebbing mode. Plant Cell 26: 3538-3555; 10.1105/tpc.114.127381
Huang, W., Liu, H., McCormick, S., and Tang, W. 2014. Tomato pistil factor LeSTIG1 promotes in vivo pollen tube growth by binding to phosphatidylinositol 3-phosphate and the extracellular domain of LePRK2. Plant Cell 26: 2505-2523; plantcell.org/content/26/6/2505
Zheng, B., He, H., Zheng, Y., Wu, W. and McCormick, S. 2014. An ARID domain-containing protein within nuclear bodies is required for sperm cell formation in Arabidopsis thaliana. PLoS Genetics plosgenetics.org/article/info:doi/10.1371/journal.pgen.1004421
McCormick, S. 2013. Pollen. Current Biology 23: R988-R990; doi: 10.1016/j.cub.2013.08.016
Zhao, X-Y., Wang, Q., Li., S., Ge., F-R., Zhou, L-Z., McCormick, S. and Zhang, Y. 2013. The juxtamembrane and carboxy-terminal domains of Arabidopsis PRK2 are critical for ROP-induced growth in pollen tubes. J. Experimental Botany 64: 5599-5610; doi: 10.1093/jxb/ert323
Boavida, L.C., Qin, P., Broz, M., Becker, J.D. and McCormick, S. 2013. Arabidopsis tetraspanins are confined to discrete expression domains and cell types in reproductive tissues and form homo- and hetero-dimers when expressed in yeast. Plant Physiology 163: 696-712; doi: 10.1104/pp.113.216598Li, S., Zhou, L-Z., Feng, Q-N., McCormick, S. and Zhang, Y. 2013. The C-terminal hypervariable domain targets Arabidopsis ROP9 to the invaginated pollen tube plasma membrane. Molecular Plant 6:1362-1364; doi: 10.1093/mp/sst098