Alfalfa nodulation by Sinorhizobium fredii does not require sulfated Nod-factors

Abstract

Rhizobium strain 042B(s) is able to nodulate both soybean and alfalfa cultivars. We have demonstrated, by mass spectrometry, that the nodulation (Nod) factors produced by this strain are characteristic of those produced by Sinorhizobium fredii, which typically nodulates soybean; they have 3–5 N-acetylglucosamine (GlcNAc) residues, a mono-unsaturated or saturated C16, C18 or C20 fatty-acyl chain, and a (methyl)fucosyl residue on C6 of the reducing-terminal GlcNAc. In order to study Rhizobium strain 042B(s) and its nodulation behaviour further, we introduced an insertion mutation in the noeL gene, which is responsible for the presence of the (methyl)fucose residue on the reducing terminal GlcNAc of the Nod-factors, yielding mutant strain SVQ523. A plasmid (pHM500) carrying nodH, nodP and nodQ, the genes involved in sulfation of Nod-factors on C6 of the reducing-terminal GlcNAc, was introduced into SVQ523, generating SVQ523.pHM500. As expected, strain SVQ523 produces unfucosylated Nod-factors, while SVQ523.pHM500 produces both unfucosylated and unfucosylated sulfated Nod-factors. Plant tests showed that soybean nodulation was reduced if the inoculant (SVQ523.pHM500) produced sulfated Nod-factors. In the Asiatic alfalfa cultivar Baoding, SVQ523 (absence of a substitution at C6) failed to nodulate, but both 042B(s) (fucosyl at C6) and SVQ523.pHM500 (sulfate at C6) formed nodules. In contrast, SVQ523 showed enhanced nodulation capacity with the western alfalfa cultivars ORCA and ARC. These results indicate that Nod-factor sulfation is not a requisite for S. fredii to nodulate alfalfa.

Priming of rhizobial nodulation signaling in the mycosphere accelerates nodulation of legume hosts

“…Nar and Kae have been demonstrated as nod gene inducers of many rhizobia, for instance, B. japonicum, Bradyrhizobium sp. strain ORS285, Sinorhizobium fredii and Rhizobium leguminosarum (Kosslak et al, 1987;Begum et al, 2001;Noreen et al, 2003;Renier et al, 2011), and a mixtures of flavonoids is more effective in inducing nod genes in comparison to a single flavonoid (Cooper, 2004;Hassan & Mathesius, 2012). Consistently, nodD1 of B. japonicum and B. elkanii was also induced during cocultivation with Ph, suggesting that Ph-mediated nod genes induction occurred in many types of rhizobium.…”

“…japonicum , Bradyrhizobium sp. strain ORS285, Sinorhizobium fredii and Rhizobium leguminosarum (Kosslak et al ., 1987; Begum et al ., 2001; Noreen et al ., 2003; Renier et al ., 2011), and a mixtures of flavonoids is more effective in inducing nod genes in comparison to a single flavonoid (Cooper, 2004; Hassan & Mathesius, 2012). Consistently, nodD1 of B. japonicum and B .…”

Two Broad Host Range Rhizobial Strains Isolated From Relict Legumes Have Various Complementary Effects on Symbiotic Parameters of Co-inoculated Plants

“…It can be seen that pseudonodules formed on M. sativa roots in all variants of inoculation did not contain any rhizobia ( Figure 3A–C ), although bacterial cells of the strain Ach-343 were present on the root surface ( Figure 3B ). It is known that M. sativa is a highly specific plant that forms a symbiosis only with bacteria Sinorhizobium meliloti and S. medicae , although it has been shown that some other rhizobial strains can also nodulate this plant species ( Noreen et al, 2003 ; Torres Tejerizo et al, 2011 ). In contrast, in nodules on T. pratense roots inoculated with the strains Opo-235(pMP4655) or Ach-343(pHC60) the corresponding bacteria were present ( Figure 3D,E ), while in the variant of co-inoculation only nodules with the strain Opo-235(pMP4655) were observed ( Figure 3F ).…”

The Role of GmSnRK1-GmNodH Module in Regulating Soybean Nodulation Capacity

“…In alfalfa, the expression of nodulin gene MtENOD12 was significantly inhibited after inoculation with a nodH mutant compared to the wild-type Rhizobium meliloti , suggesting the sulfated Nod factors are required for nodulation by R. meliloti [ 29 ]. However, alfalfa nodulation by Sinorhizobium fredii does not required sulfated Nod-factors [ 30 ].…”