Figure 1 from Flavonoids as Signaling Molecules and Regulators of Root Nodule Development | Semantic Scholar (2025)

This mini-review highlights some of the recent studies on the three major types of root endosymbioses, suggesting a common symbiotic signaling pathway for both plant-fungal and plant bacterial endosys between legumes and actinorhiza-forming fagales.

A key role played by Ca(2+) in sensing and transducing plant-specific flavonoid signals in rhizobia is demonstrated and a new perspective in the flavonoids-NodD paradigm of nod gene regulation is opened up.

One group of proteins secreted by rhizobia have homologues in bacterial pathogens and may have been co-opted by rhzobia for symbiotic purposes.

The results suggest that ANE may contain compound(s) that promote the legume–rhizobia symbiotic relationship and plant signaling and HPLC profiles and a root hair deformation assay suggested that ANe elicits production of compounds similar to the Nod factor, which are normally induced by the plant signaling molecule luteolin.

The plant microbe interaction, mechanism of nodulation and nitrogen fixation as well as several direct and indirect mechanism of PGPRs for plant growth promotion and effect of rhizobium and PGPR co-inoculation in legume are discussed.

In this introductory chapter, a brief review of co-evolution of secondary metabolites not only to complete the biological process but also to compete with each other for survival is presented.

expression of autoactive version of DMI3 was shown to be sufficient to trigger downstream developmental processes leading to the induction of spontaneous nodulation in the absence of rhizobia, and lay the basis for the potential development of a biotechnological approach towards improvement of rice production.

The results concur that the positive interaction of non-rhizobial endophytic yeast with rhizobIAL strain may emerge as a novel bio-inoculant for sustainable pulse productivity.

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It is shown here that growth of the plant under nitrogen-limiting conditions results in the enhancement of expression of the flavonoid biosynthesis genes chalcone synthase and isoflavone reductase and in an increase of root flavonoids and is oflavonoid production.

The development of an assay system for the detection of plant-derived stimulatory biofactors has now led to the isolation and identification of the compounds which are responsible for the activation of the nod genes, and hydroxylated flavonoid compounds from plants are isolated.

The induction of nodABC expression by alfalfa exudates demonstrates host-symbiont signaling at an early stage in nodule development.

All the compounds identified as nod gene inducers in the root are flavonoids, indicating that other compounds with nod gene activator capacity may have little contribution, if any, to nod gene activation.

Genetic evidence is presented that root flavonoids are necessary for nodule initiation in M. truncatula and suggestions that they act as auxin transport regulators are suggested.

The characteristics of several plant-specified compounds that activate the transcription of the pRL1JI nodABCIJ and nodFE genes are described and a novel phenomenon is presented, namely that other, naturally occurring compounds can antagonize this induction.

This paper summarises the principal findings to date from an array of biochemical, chemical analytical and molecular techniques used to investigate mechanisms of flavonoid degradation exhibited in rhizobia, changes in Flavonoid content of legume root exudates during incubation with rhzobia, the fate of a nod gene-inducing flavonoids during Nod factor synthesis and the nature of gene expression in Rhizobia during exposure to Flavonoids.

Direct, genetic evidence is provided that isoflavones are essential for nodulation of soybean roots because of their ability to induce the nodulation genes of Bradyrhizobium japonicum.

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