The early nodulin gene SrEnod2 from Sesbania rostrata is inducible by cytokinin

Abstract

Summary The structure and expression of the early nodulin gene Enod2 from the stem‐nodulated tropical legume Sesbania rostrata (SrEnod2) was examined. Genomic clones carrying the single SrEnod2locus were isolated and the DMA sequence of the gene was determined. The SrEnod2 gene was found to lack introns and to encode a protein consisting primarily of a 55‐fold repeat of short proline‐rich oligopeptides. A putative signal sequence, which may be responsible for targeting of the Enod2 protein to the cell wall, was found to precede this repeat. The temporal expression of the SrEnod2 gene was found to be different in S. rostrata stem versus root nodules induced by Azorhizobium caulinodans ORS571. SrEnod2 gene expression was shown to be induced specifically and rapidly by physiologically significant concentrations of exogenously supplied cytokinins. The SrEnod2gene was also found to be highly expressed in S. rostrata crown gall tumors induced by wild‐type Agrobacterium tumefaciens strains, but not in tumors induced by an A. tumefaciens strain carrying a mutation in the cytokinin biosynthesis gene 4. Implications of these observations with regard to cytokinin‐induced plant gene expression and a possible role for cytokinin as a symbiotic signal are discussed.

Conserved regulation of the soybean early nodulin ENOD2 gene promoter in determinate and indeterminate transgenic root nodules

“…At A number of temporally and spatially regulated plant genes expressed specifically during nodule development have been characterized (Govers et a/., 1987;van Kammen, 1984;Nap and Bisseling, 1990;Sandal eta/., 1987). Early nodulin genes are expressed shortly after infection with Rhizobia, and are most likely involved in infection and nodule morphogenesis rather than nodule functioning (Nap and Bisseling, 1990 (Dehio and de Bruijn, 1992 …”

Accumulation ofENOD2-Like Transcripts in Non-Nodulating Woody Papilionoid Legumes

“…5), which is consistent with the response of other ENOD2 genes to ATIs and cytokinins. However, SrENOD2 RNA is present in roots of S. rostrata 2 to 48 h after exposure to benzylaminopurine even though no pseudonodules develop (Dehio and de Bruijn, 1992).…”

“…5). SrENOD2 genes in S. rostrata are similar to SjENOD2 in that they have a specific response to one treatment, cytokinin (Dehio and de Bruijn, 1992), whereas, SjENOD2 responds to TIBA. Sprent (1994) and others have questioned whether legumes considered non-nodulators lost the capacity to nodulate over time or never acquired it.…”

“…After inoculation with rhizobia or treatment with ATIs or cytokinins, nodules and pseudonodules become visible on roots in 7 to 14 d, and ENOD2 transcripts can be detected in 4 to 10 d (Hirsch et al, 1989(Hirsch et al, , 1993(Hirsch et al, , 1997Govers et al, 1990;Dehio and de Bruijn, 1992;Scheres et al, 1992;Cooper and Long, 1994;Wu et al, 1996). In our experiment pseudonodules developed on the TIBA-treated roots of the nodulating controls, alfalfa and M. amurensis, and zeatin induced pseudonodules in alfalfa (Fig.…”

Characterization and Gene Expression of Nodulin Npv30 from Common Bean

“…The expression of some early nodulin genes, such as enodl2, can be induced by rhizobial lipooligosaccharides known as nodulation (Nod) factors (Pichon et al, 1992;Journet et al, 1994). However, others, such as enod2, cannot be induced by nodulation factors, and they seem to be under hormonal regulation (Dehio and Bruijn, 1993;Cooper and Long, 1994).…”