salinity is among important soil stresses adversely affecting the process of nitrogen (n) fixation in leguminous plants in different parts of the world. it has been indicated that salinity can inhibit the early stages of nodulation process between bacterium and the host plant including the exchange of signal molecules (nod gene inducers). there has not been any research regarding the effects of...

Alfalfa (Medicago sativa L.) seeds and roots can create complex rhizosphere effects by releasing flavonoids that induce nodulation (nod) genes in Rhizobium meliloti. Previous reports identified luteolin and 4,4'-dihydroxy-2'-methoxychalcone as strong inducers that are released from seeds and roots, respectively, and 4',7-dihydroxyflavone and 4',7-dihydroxyflavanone as weaker inducers which are ...

The early steps of symbiotic nodule formation by Rhizobium on plants require coordinate expression of several nod gene operons, which is accomplished by the activating protein NodD. Three different NodD proteins are encoded by Sym plasmid genes in Rhizobium meliloti, the alfalfa symbiont. NodD1 and NodD2 activate nod operons when Rhizobium is exposed to host plant inducers. The third, NodD3, is...

Flavonoid signals from alfalfa (Medicago sativa L.) induce transcription of nodulation (nod) genes in Rhizobium meliloti. Alfalfa roots release three major nod-gene inducers: 4',7-dihydroxyflavanone, 4',7-dihydroxyflavone, and 4,4'-dihydroxy-2'-methoxychalcone. The objective of the present study was to define temporal relationships between synthesis and exudation for those flavonoids. Requireme...

Luteolin, a flavone present in seed exudates of alfalfa, induces nodulation genes (nod) in Rhizobium meliloti and also serves as a biochemically specific chemoattractant for the bacterium. The present work shows that R. meliloti RCR2011 is capable of very similar chemotactic responses towards 4',7-dihydroxyflavone, 4',7-Dihydroxyflavanone, and 4,4'-dihydroxy-2-methoxychalcone, the three princip...

Two major dendritic cell (DC) subsets have been described in the pancreas of mice: The CD11c+ CD8α- DCs (strong CD4+ T cell proliferation inducers) and the CD8α+ CD103+ DCs (T cell apoptosis inducers). Here we analyzed the larger subset of CD11c+ CD8α- DCs isolated from the pancreas of pre-diabetic NOD mice for genome-wide gene expression (validated by Q-PCR) to elucidate abnormalities in under...

Six nod box regulatory sequences are present in the Rhizobium meliloti genome. We have analysed the DNA region located downstream of nod box n6, and identified three open reading frames, designated nolQa, nolQb and nolS. LacZ fusions in these ORFs are not induced by classical nod gene inducers, which indicates that their expression either is not under the control of the nod box, or involves ano...

Flavonoid signals from alfalfa (Medicago sativa L.) seed and root exudates induce transcription of nodulation (nod) genes in Rhizobium meliloti. The flavone luteolin previously was isolated from alfalfa seeds by other workers and identified as the first nod gene inducer for R. meliloti. Our recent study of 'Moapa 69' alfalfa root exudates found no luteolin but did identify three other nod gene ...