Skip to main content
ARS Home » Midwest Area » Ames, Iowa » Corn Insects and Crop Genetics Research » Research » Publications at this Location » Publication #110019
Title: A SOYBEAN PLASTID-TARGETED NADH-MALATE DEHYDROGENASE: CLONING AND EXPRESSION ANALYSES

Author
item IMSANDE, JOHN - IOWA STATE UNIVERSITY
item Palmer, Reid
item BERKEMEYER, MATTHIAS - PFLANZENPHYSIOLOGIE BIOL
item SCHEIBE, RENATE - PFLANZENPHYSIOLOGIE BIOL
item PITTIG, JOACHIM - TECHNISCHE UNIVERSITAT MU
item SCHUMANN, U - TECHNISCHE UNIVERSITAT MU
item GIETL, CHRISTINE - TECHNISCHE UNIVERSITAT MU

Submitted to: American Journal of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/14/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: Soybean plants use nitrogen in the roots, leaves, flowers, seeds, and pods. Many biochemical processes are necessary to make the plant seeds. One product of biochemical reactions are compounds called proteins. Enzymes are a type of protein that speed up or slow down biochemical reactions. In soybean we have found a specialized form of an enzyme that is very abundant tin certain root structures, seeds, and pods. It is proposed that this novel enzyme helps in nitrogen absorption in roots and supports rapid production of storage proteins in soybean seeds. Soybean seeds are usually between 38 to 44 percent protein, so this novel enzyme is very important in maintaining seed protein content. Results of this research provide consumers with a source of high protein food for balanced diets.

Technical Abstract: A typical soybean plant assimilates nitrogen rapidly both in active root nodules and developing seeds and pods. Oxaloacetate and 2-ketoglutarate are major acceptors of ammonia during rapid nitrogen assimilation. Oxaloacetate can be derived from the TCA cycle and it also can be synthesized from phosphoenolpyruvate and carbon dioxide by phosphoenolpyruvate carboxylase. An active malate dehydrogenase is required to facilitate carbon flow from phosphoenolpyruvate to oxaloacetate. We report the cloning and sequence analyses of a complete and novel malate dehydrogenase gene in soybean. The derived amino acid sequence is highly homologous to the nodule-enhanced malate dehydrogenases from alfalfa and pea in terms of the transit peptide and the mature subunit. Furthermore, the mature subunit exhibits a very high homology to the plastid-localized NAD-dependent malate dehydrogenase from Arabidopsis thaliana, which has a completely different transit peptide. The soybean nodule-enhanced malate dehydrogenase was abundant in root nodules, immature soybean seeds, and pods. Only trace amounts of the enzyme were found in leaves and nonnodulated roots. We propose that this novel malate dehydrogenase facilitates nitrogen assimilation in soybean root nodules and supports rapid synthesis of the seed storage proteins in the developing soybean seeds.