• Ph.D. 1982, Michigan State University
• B.A. 1976, Michigan State University

My research interests involve investigating questions in developmental and molecular biology using a variety of methods. In particular, the research in my laboratory is focused on the plant genes required for development of a specialized structure; the root nodule, in which nitrogen is fixed by the microsymbiont, Rhizobium. As part of this effort, we are investigating gene expression in several mutants of white sweetclover that exhibit a range of phenotypes blocked early in nodule development. We are currently analyzing the mutant alleles for espression of cloned nodulin (nodule-specific) genes, including Enod2, Enod8, and Enod12, as well as genes such as chalcone synthase that might indicate a defense response to Rhizobium.

We have recently shown that the non-nodulating sym-1 and sym-3 alleles in particular may hold the key to understanding signal transduction in nodule development. Although these alleles form no nodules in response to Rhizobium, all of them form pseudonodules when treated with an auxin transport inhibitor. This suggests that the auxin transport inhibitor may be mimicking a second signal, produced by the plant, that is required for nodule organogenesis. We have incorporated these findings into a recently proposed model of the signal transduction pathways required for nodule morphogenesis. Our long range goals include isolating the genes represented by the sweetclover mutants for direct structural studies of the genes and their products, followed by analysis of their function in transgenic plants.

• Ultrup, L.J., A.J. Carey, and J.H. Norris. 1993. Five nodulation mutants of white sweetclover (Melilotus alba Desr.) exhibit distinct phenotypes blocked at root hair curling, infection thread development, and nodule organogenesis. Plant Physiology 103: 925-932.


• Wu, C., R. Dickstein, A.J. Carey, and J.H. Norris. 1996. The auxin transport inhibitor N-(1-naphthyl) phthalamic acid elicits pseudonodules on non-nodulating mutants of white sweetclover (Melilotus alba Desr.). Plant Physiology 110: 501-510.


• Ultrup, L.J., and J.H. Norris. 1996. Nodulin gene expression in effective root nodules of white sweetclover (Melilotus alba Desr.) and in ineffective nodules elicited by mutant strains of Rhizobium meliloti. Journal of Experimental Botany 47: 195-202.