Rice ENOD40: isolation and expression analysis in rice and transgenic soybean root nodules

Abstract

SummaryThe early nodulin ENOD40 has been proposed as playing a pivotal role in the organogenesis of legume root nodules. We have isolated the ENOD40 gene homologues ObENOD40 and OsENOD40 from the wild and cultivated rice genotypes Oryza brachyantha and Oryza sativa, respectively. Rice ENOD40s contain a sequence at the 5Ј end (region I) for encoding an oligopeptide that is highly conserved in all legume ENOD40s. Furthermore, at the 3Ј end (region II), the nucleotide sequence of rice ENOD40s exhibited a considerable homology to the corresponding region in legume ENOD40s. Among various organs of the rice plant, expression of OsENOD40 was detected only in stems. In situ hybridization studies revealed that, within the stem, transcription of OsENOD40 is confined to parenchyma cells surrounding the protoxylem during the early stages of development of lateral vascular bundles that conjoin an emerging leaf. Expression pattern of OsENOD40 promoter-GUS fusion in nodules developed on transgenic hairy roots of soybean was also found to be restricted to peripheral cells of nodule vascular bundles, thus evidencing that rice ENOD40 promoter activity is essentially the same as that of soybean ENOD40. Taken together, these results strongly suggest that OsENOD40 and legume ENOD40s share common, if not identical, functions in differentiation and/or function of vascular bundles.

Root-derived CLE glycopeptides control nodulation by direct binding to HAR1 receptor kinase

“…G. max Enrei seedlings (5 DAG) were inoculated with A. rhizogenes K599 harbouring either a CLE-RS2-overexpressing construct or an empty vector. Hairy root transformation was induced 37 , and the plants were grown on vermiculite. Three weeks after inoculation, untransformed roots were removed, and plants with green fluorescent protein-positive hairy roots were transplanted into fresh sterilized vermiculite.…”

Medicago truncatula plants overexpressing the early nodulin gene enod40 exhibit accelerated mycorrhizal colonization and enhanced formation of arbuscules

“…In general, enod40 transcripts were found in cells that transport carbohydrates to strong sinks or become those sinks, such as the nodule and lateral root primordium or the peripheral cells of vascular bundles (9,10,24,25). Indeed, in developing rice leaves, enod40 expression changed during the source͞sink transition (26). One possibility is that enod40 transcripts in mycorrhizal roots are involved in the control of carbohydrate supply or partitioning into specific cells.…”

“…Interestingly, enod40 genes are not restricted to legumes. Homologs of enod40 are known from tobacco (12) and rice (26), host plants of AM fungi, but were not found in the genome of the nonhost Arabidopsis thaliana. A search for enod40 homologs from various nonlegumes could result in a correlation between the finding of enod40 sequences and host plants.…”

Opportunities for increasing water productivity of CGIAR crops through plant breeding and molecular biology.

“…The use of green manure is frequently advocated but it is often limited by water supply. As water becomes scarcer, it is even less likely (Kouchi et al, 1999). Rhizobium is closely related to Agrobacterium, another bacterium that naturally forms relations with dicotyledons but not with cereals.…”