Characterization of ENOD2 cDNAs in Maackia amurensis Rupr. & Maxim. (Amur Maackia)

Abstract

ENOD2 and other early nodulin genes are conserved among legumes studied to date and might function as markers for the potential of legumes to nodulate. Early nodulin genes have been characterized only among herbaceous legumes. We are interested in understanding the nature of ENOD2 in a nodulating, woody legume. A 561-bp MaENOD2 PCR fragment was used as a probe to screen a cDNA library from nodules ≈1 mm in diameter on roots of Amur maackia, the only temperate and horticulturally desirable leguminous tree species known to nodulate. Five cDNAs were selected for nucleotide sequence analysis. Sequences were determined by using automated dideoxy sequencing and analyzed for identity to other genes with the Genetics Computer Group (GCG) program. The cDNA clones show 68% to 74% identity at the nucleic acid level with ENOD2 genes of Sesbania rostrata Brem. & Oberm., Glycine max (L.) Merrill, and Lupinus luteus L. Southern and northern analyses are being conducted to investigate the possibility of a gene family and to show differential and temporal production of transcripts, respectively. These studies provide new information about nodulins of woody legumes and are being used to facilitate related research on molecular barriers to nodulation in the closely related, non-nodulating tree species Cladrastis kentukea (Dum.-Cours.) Rudd (American yellowwood) and Sophora japonica L. (Japanese pagodatree).