Research Summary and Publication lists of recent important works.
The general area of my research interest is in the genetic regulation of plant cell development and differentiation. Research of this nature can be applied to a variety of plant systems, but seeds are particularly well suited to study these processes. Furthermore, seeds are an important agricultural product and are of major importance as primary or secondary sources of food.
During their development, seeds accumulate large amounts of protein, carbohydrate, and lipid that are subsequently digested and made available to the developing embryo. The nature and proportion of these storage products varies among different plant species, although the mechanisms regulating their synthesis are conserved. In a number of instances, mutations have been identified that qualitatively or quantitatively alter the synthesis of these compounds. In addition to modifying the nutritional value of secondary by -products of the seeds, these mutants provide a starting point to study the regulatory mechanisms controlling the synthesis and deposition of these storage compounds.
Seed storage proteins are synthesized in large quantities over a limited period of time. In dicots, these proteins are deposited in the embryo as well as in the endosperm of the developing seed. In cereals, deposition primarily occurs in the endosperm, where storage proteins account for 60-70% of the total protein. Storage proteins are deficient in several essential amino acids, and because they account for the majority of the protein, seed proteins generally have limited nutritional value. One important area of research is directed at increasing the nutritional value of seed proteins.
The storage proteins of different cereals have distinct structural characteristics that are responsible for their unique food-making characteristics. Only recently has research begun to define the structural features that are responsible for their unique biochemical properties.
We are studying a number of mutations that alter the synthesis of maize seed storage proteins. Although some of these mutations affect regulatory genes that control transcription of the storage protein genes, the precise mechanisms by which others alter storage protein synthesis are unknown. We have also recently found that structural interactions between the different types of storage proteins appear to influence their assembly into protein bodies, and ultimately the quality characteristics of the seed.
Habben, J.E., Moro, G.L., Hunter, B.G., Hamaker, B.R. and Larkins, B.A. (1995) Elongation factor1-a is highly correlated with the lysine content of maize endosperm. Proc.Natl. Acad.Sci.USA 92:8640-8644.
Grafi, G. and Larkins, B.A. (1995) Endoreduplication in maize endosperm: Involvement of M phase-promoting factor inhibition and induction of S phase-related kinases. Science 269, 1262-1264.
Li, C.-P. and B.A. Larkins (1996) Expression of protein disulfide isomerase is elevated in the endosperm of the maize floury2 mutant. Plant Molecular Biology 30, 873-882.
Moro, G.L., Habben, J.E., Hamaker, B.R., and Larkins, B.A. (1996) Characterization of the variability in lysine content for normal and opaque2 maize endosperm. CropScience 36, 1651-1659.
Grafi, G., Burnett, R.J., Helentjaris, T., Larkins, B.A., DeCaprio, J.A., Sellers, W.R., and Kaelin,W.G. Jr. (1996) A maize cDNA encoding a member of the retinoblastoma protein family: Involvement in endoreduplication. Proceedings of the National Academy of Sciences, USA 93, 8962- 8967.
Clore, A.M., Dannenhoffer, J.M., and Larkins, B.A. (1996) EF-1 is associated with a cytoskeletal network surrounding protein bodies in maize endosperm cells. Plant Cell 11, 2003-2014.
Coleman, C.E., Herman, E.M., Takasaki, K., and Larkins, B.A. (1997) The maize -zein sequesters -zein and stabilizes its accumulation in protein bodies of transgenic tobacco endosperm. Plant Cell 12, 2335-2345.
Gillikin, J.W., Zhang, F., Coleman, C.E., Bass, H.W., Larkins, B.A. and Boston, R.S. (1997) A defective signal peptide tethers the floury-2 zein to the endoplasmic reticulum membrane. Plant Physiology 114: 345- 352.
Coleman, C.E., Clore, A.M., Ranch, J.P., Higgins, R., Lopes, M.A. and Larkins, B.A. (1997) Expression of a mutant -zein creates the floury2 phenotype in transgenic maize.