Lotus japonicus contains two distinct ENOD40 genes that are expressed in symbiotic, nonsymbiotic, and embryonic tissues

ENOD40, an early nodulin gene, has been postulated to play a significant ro le in legume root nodule ontogenesis, We have isolated two distinct ENOD40 genes from Lotus japonicus, The transcribed regions of the two ENOD40 genes share 65% homology, while the two promoters showed no significant homology , Both transcripts encode a putative dodecapeptide similar to that identifi ed in other legumes forming determinate nodules, Both ENOD40 genes are coor dinately expressed following inoculation of roots with Mesorhizobium loti o r treatment with purified Nod factors. In the former case, mRNA accumulatio n could be detected up to 10 days following inoculation while in the latter case the accumulation was transient. High levels of both ENOD40 gene trans cripts were found in nonsymbiotic tissues such as stems, fully developed fl owers, green seed pods, and hypocotyls, A relatively lower level of both tr anscripts was observed in leaves, roots, and cotyledons. In situ hybridizat ion studies revealed that, in mature nodules, transcripts of both ENOD40 ge nes accumulate in the nodule vascular system; additionally, in young seed p ods strong signal is observed in the ovule, particularly In the phloem and epithelium, as well as in globular stage embryos.