RESEARCH INTEREST

Modification of soybean seed composition; Rhizobium-soybean symbiosis


RESEARCH

Modification of soybean seed composition.
Soybean is an important source of edible vegetable oil and protein throughout the world and is used in a multitude of food and industrial applications. Even though soybeans are a rich source of protein for livestock and humans, the nutritional quality of soybean proteins is not optimal. Some of the problems associated with soybean proteins include (1) presence of anti-nutritional factors such as trypsin inhibitor, (2) undesirable beany flavor, (3) elicitation of allergic reactions in susceptible individuals (4) poor digestibility of soybean proteins, and (5) deficiency in sulfur-containing amino acids. The goal of our research program is to improve the overall quality of soybean seed composition by molecular biological approaches.

Rhizobium-soybean symbiosis.
Another area of our research is focused on biological nitrogen fixation using the model symbiosis between soybeans and Sinorhizobium fredii USDA257. Efficient nitrogen fixation greatly enhances the yield of protein-rich seeds. Our research is focused on the molecular basis of host specificity using the model symbiosis between soybeans and S. fredii USDA257. This strain nodulates primitive but not agronomically improved soybean cultivars. Our laboratory is currently focusing on the cultivar-specificity genes of S. fredii. What do they encode? What regulates their expression? And how are the responses are made host specific? Answers to such questions will enable us to rationally manage and enhance the process of biological nitrogen fixation and improve the overall soybean protein quality.


SELECTED PUBLICATIONS

Natarajan, S. S., Krishnan, H. B., Lakshman, S., and Garrett, W. M. 2009. An efficient extraction method to enhance analysis of low abundant proteins from soybean seed. Analytical Biochemistry (in press).

Krishnan, H. B. 2008. Preparative procedures markedly influence the appearance and structural integrity of protein storage vacuoles in soybean seeds. J. Agric. Food Chem. 56:2907-12.

 Krishnan, H. B., and Chronis, D. 2008. Functional nodFE genes are present in Sinorhizobium sp. strain MUS10, a symbiont of the tropical legume Sesbania rostrata. Applied and Environmental Microbiology 74:2921-23.

 Han, S. H., Kim, C. H., Lee, J. H., Park, J. Y. Cho, S. M., Park, S. K., Kim, K. Y., Krishnan, H. B., and Kim, Y. C. 2008. Inactivation of pqq genes of Enterobacter intermedium 60-2G reduces antifungal activity and induction of systemic resistance. FEMS Microbiology Letters 282:140-46.

Bilyeu, K. D., Zeng, P., Coello, P., Zhang, Z. J., Krishnan, H. B., Bailey, A, Beuselinck, P. R., and Polacco, J. C. 2008. Quantitative conversion of phytate to inorganic phosphorus in soybean seeds expressing a bacterial phytase. Plant Phys. 146:468-77.

Mahmoud, A. A., Sukumar, S., and Krishnan, H. B. 2008. Interspecific rice hybrid of Oryza sativa x Oryza nivara reveals a significant increase in seed protein content. J. Agric. Food Chem. 56:476-82.

Phartiyal, P., Kim, W-S., Cahoon, R.E., Jez, J.M., and Krishnan, H.B. 2008. The role of 5'-adenylylsulfate reductase in the sulfur assimilation pathway of soybean: molecular cloning, kinetic characterization, and gene expression. Phytochemistry 69:356-364.