Since the induction of the early nodulin gene FNODl2 in the epidermis and the formation of a nodule primordium in the inner cortex were not affected, we conclude that more than one Nod factor-perception mechanism is active. Furthermore, we show that symp-mediated control of infection-thread growth was affected by the bacterial nodulation gene nodO.Rhizobium bacteria have the ability to induce a developmental process in the root of leguminous plants that results in the formation of a new organ, the root nodule. These new organs create the environment in which the bacteria fix nitrogen to ammonia, which can subsequently be utilized by the plant.The symbiotic interaction of Rhizobium sp. bacteria and leguminous plants is set in motion by the exchange of signal molecules. Plant-excreted flavonoids induce the expression of bacterial nodulation (nod) genes, which are responsible for the synthesis of specific lipochitin oligosaccharides, named Nod factors (Lerouge et al., 1990;Spaink et al., 1991). Nod factors consist of a tetra-or pentameric N-acetylglucosamine backbone with a fatty acyl chain at the nonreducing terminal sugar moiety. Substituents at the terminal sugar residues and the structure of the acyl chain determine the differences in biological activity and host specificity (for review, see Carlson et al., 1994).The role of Nod factor structure in host specificity is exemplified as follows: alfalfa (Medicago sativa) belongs to the cross-inoculation group that can be nodulated by Rhi- zobium meliloti, which produces Nod factors with a sulfate group at the reducing sugar (Lerouge et al., 1990). In contrast, pea (Pisum sativum) is nodulated by Rhizobium leguminosarum bv viciae, which produces Nod factors that lack a substitution at that position (Spaink et al., 1991). When the host-specificity genes nodH, nodP, and nodQ, which are responsible for the sulfation of the Nod factors in R. meliloti, are introduced into R. leguminosarum bv viciae these bacteria can now induce noninfected, nodule-like structures on alfalfa but concomitantly lose their ability to nodulate pea and vetch (Faucher et al

No abstract

No abstract

A novel bioactive fluorescent nodulation (Nod) factor, NodRlv-IV(BODIPY FL-C16), has been synthesized by attaching a BODIPY FL-C16 acyl chain to the primary amino group of chitotetraose deacetylated at the nonreducing terminus by recombinant NodB. The binding of the fluorescent Nod factor to root systems of Vicia sativa was investigated with fluorescence spectral imaging microscopy (FSPIM) and fluorescence ratio imaging microscopy (FRIM). Spatially resolved fluorescence spectra of living and labeled Vicia sativa root systems were measured by FSPIM. Strong autofluorescence, inherent to many plant systems when excited at 488 nm, was corrected for by utilizing the difference in fluorescence emission spectra of the autofluorescence and NodRlv-IV(BODIPY FL-C16). A methodology is presented to break down the in situ fluorescence emission spectra into spatially resolved autofluorescence and BODIPY FL fluorescence spectra. Furthermore, an FRIM method was developed for correcting autofluorescence in fluorescence micrographs for this system. After autofluorescence correction it was shown that NodRlv-IV(BODIPY FL-C16) was concentrated in the root hairs, but was also bound to other parts of the root surface.