Molecular basis of symbiotic host specificity in rhizobium meliloti: nodH and nodPQ genes encode the sulfation of lipo-oligosaccharide signals

Functional redundancy of genes for sulphate activation enzymes in Rhizobium sp. BR816

“…In the event that BR816 nodP2 and nodQ2 do not belong to the same operon and the mutation in nodP2 provokes a truncated but active ATP suiphurylase not affecting a putative nodP internal nodQ promoter sequence, it is possible that the NF sulphur activation complex is still active, although the amount of PAPS for NF sulphation would be expected to be lower (as is the case for S. meliloti nodQ2 or nodQ2 single mutants), since the expressed nodPl is effectively mutated. Roche et al (1991) demonstrated by TLC and HPLC that in S. meliloti both nodPQ copies approximately equally contributed to NF sulphation. Additionally, we constructed a distinct BR816 nodQ2 deletion mutant by exchange of a nodQ2 internal SalI fragment for the Sp/Sm resistance cassette, obtaining CFNE206.…”

“…In these three strains the NF sulphation genes are organized in one nodHPQ operon whereas in S. meliloti, nodH and nodPQ are separated by nodEF and nodG (Debelle & Sharma 1986;Faucher et al, 1988;Cervantes et al, 1989). For nodulation of alfalfa by S. meliloti, the sulphated NF is indispensable (Roche et al, 1991 ;Truchet et al, 1991), possibly because the sulphate moiety protects the NF against plant-chitinase degradation (Schultze et al, 1993;Staehelin et al, 1994). Previously, we isolated the nodHPQ operon from R. tropici strain CFN299 and showed that the sulphate substituent was detrimental for nodulation of highnitrogen-fixing bean cultivars (Laeremans et al, 1996).…”

“…On the reducing end, sugar modifications such as a fucosyl residue (Price et al, 1992;Sanjuan et al, 1992), an arabinosyl residue (Mergaert et al, 1993) or a mannosyl moiety (Folch-Mallol et al, 1996) can be present (for an overview of Nod factor structures and nodulation genes, see Denarie et al, 1996). Other reducing end side decorations include an 0-acetylation (Price et al, 1992) and an 0-sulphation, the latter modification either directly linked to the C6 of the nonreducing sugar (for S. meliloti, see Lerouge et al, 1990) or on a methylfucosyl group (for Rhizobium sp.…”

“…the Nod factors, also called lipo-chitin oligosaccharides (LCOs). Physiological effects of the LCOs on their leguminous host plants include induction of root hair curling, formation of pre-infection threads, division of cortical root cells and, in some cases, even the formation of nodule-like structures (Truchet et al, 1991 ; reviewed by Spaink, 1996). The LCOs consist of a backbone of three to six 1,4-p-linked N-acetylglucosamine units linked to a fatty acid group at the non-reducing end, which also contains additional strain-specific substituents.…”

Nod factor‐induced host responses and mechanisms of Nod factor perception

“…The chitin core is then modified by the action of NodB, which de-A-acetylates the terminal non-reducing sugar residue"" (John et al, 1993). Subsequently, NodA transfers a fatty acid from an acyl carrier protein to K. Heidstra and T. Bisseling Roche et al (1991a, , &) Schultze et al (1995 Clark, Beltrame & Manning (1991); Firmin et al (1993) this position (Rohrig et al, 1994). The terminal sugar residues are modified by the action of other Nod proteins that synthesize or add various substituents.…”