Nodulation of white clover (Trifolium repens) in the absence ofRhizobium

Blauenfeldt, J.; Joshi, Priyavadan A.; Gresshoff, Peter M.; Caetano‐Anollés, Gustavo

doi:10.1007/bf01403948

Cited by 31 publications

(16 citation statements)

References 14 publications

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“…These data suggest that the NF signaling machinery in wild-type plants is partially active in the absence of NFs, especially in cv Sparkle. This is reminiscent of reports that certain legumes spontaneously induce nodule-like structures in the absence of rhizobia (Truchet et al, 1989;Blauenfeldt et al, 1994).…”

Section: Discussionsupporting

confidence: 57%

Nod Factors Induce Nod Factor Cleaving Enzymes in Pea Roots. Genetic and Pharmacological Approaches Indicate Different Activation Mechanisms

Ovtsyna¹,

Долгих²,

Kilanova³

et al. 2005

Plant Physiology

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Establishment of symbiosis between legumes and rhizobia requires bacterial Nod factors (NFs). The concentration of these lipochitooligosaccharides in the rhizosphere is influenced by plant enzymes. NFs induce on pea (Pisum sativum) a particular extracellular NF hydrolase that releases lipodisaccharides from NFs from Sinorhizobium meliloti. Here, we investigated the ability of non-nodulating pea mutants to respond to NodRlv factors (NFs from Rhizobium leguminosarum bv viciae) with enhanced NF hydrolase activity. Mutants defective in the symbiotic genes sym10, sym8, sym19, and sym9/sym30 did not exhibit any stimulation of the NF hydrolase, indicating that the enzyme is induced via an NF signal transduction pathway that includes calcium spiking (transient increases in intracellular Ca 21 levels). Interestingly, the NF hydrolase activity in these sym mutants was even lower than in wild-type peas, which were not pretreated with NodRlv factors. Activation of the NF hydrolase in wild-type plants was a specific response to NodRlv factors. The induction of the NF hydrolase was blocked by a-amanitin, cycloheximide, tunicamycin, EGTA, U73122, and calyculin A. Inhibitory effects, albeit weaker, were also found for brefeldin A, BHQ and ethephon. In addition to this NF hydrolase, NFs and stress-related signals (ethylene and salicylic acid) stimulated a pea chitinase that released lipotrisaccharides from pentameric NFs from S. meliloti. NodRlv factors failed to stimulate the chitinase in mutants defective in the sym10 and sym8 genes, whereas other mutants (e.g. mutated in the sym19 gene) retained their ability to increase the chitinase activity. These findings indicate that calcium spiking is not implicated in stimulation of the chitinase. We suggest that downstream of Sym8, a stress-related signal transduction pathway branches off from the NF signal transduction pathway.Establishment of symbiosis between legumes and nitrogen-fixing rhizobia results in the formation of a new plant organ, the root nodule. Rhizobia enter the host plant usually through infection of root hairs. Bacteria within root hairs induce the formation of an infection thread that grows toward the dividing cortical cells. In a later symbiotic stage, rhizobia are released from branched infection threads into the developing nodule tissue and differentiate into nitrogen-fixing bacteroids. Nodule formation is controlled by perception of rhizobial nodulation signals: the Nod factors (NFs). Flavonoids from the host plant, in conjugation with the rhizobial activator protein NodD, induce rhizobial nodulation genes (nod, nol, and noe) that are required for NF synthesis. NFs are modified lipochitooligosaccharides, i.e. chitin oligomers linked with a fatty acid replacing the N-acetyl group on their nonreducing end (Perret et al., 2000;Ovtsyna and Staehelin, 2003). On host plants, NFs induce various responses at picomolar to nanomolar concentrations. These rapid changes include root hair curling (Hac; e.g. Heidstra et al., 1994), depolarization of plasma membranes (Ehrha...

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Section: Discussionsupporting

confidence: 57%

Nod Factors Induce Nod Factor Cleaving Enzymes in Pea Roots. Genetic and Pharmacological Approaches Indicate Different Activation Mechanisms

Ovtsyna¹,

Долгих²,

Kilanova³

et al. 2005

Plant Physiology

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“…This conclusion is strongly supported by the fact that spontaneous nodules, which possess all characteristic features of normal nodules and are formed in the absence of Rhizobium and infection thread, were able to induce the endogenous plant feedback system in alfalfa clover and Lotus (Truchet et al, 1989;Caetano-Anollés et al, 1990a, b;Joshi et al, 1991;Blauenfeldt et al, 1994;Tirichine et al, 2006). AON signal intensified as nodule primordia developed (Figure 3), signifying that the increased population of dividing cells, as a result of the growth of nodule primordia, brought about stronger regulation of nodulation.…”

Section: Article In Pressmentioning

confidence: 64%

Autoregulation of nodulation (AON) in Pisum sativum (pea) involves signalling events associated with both nodule primordia development and nitrogen fixation

Kinkema

Gresshoff

2009

Journal of Plant Physiology

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“…The root nodules showed reddish to pinkish color, indicating active N 2 fixation (Blauenfeldt et al 1994). We observed no contamination of control plants.…”

Section: Plant Performancementioning

confidence: 90%

Dual benefit from a belowground symbiosis: nitrogen fixing rhizobia promote growth and defense against a specialist herbivore in a cyanogenic plant

et al. 2010

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Legume-associated nitrogen-fixing bacteria play a key role for plant performance and productivity in natural and agricultural ecosystems. Although this plant-microbe mutualism has been known for decades, studies on effects of rhizobia colonisation on legume-herbivore interactions are scarce. We hypothesized that additional nitrogen provided by rhizobia may increase plant resistance by nitrogen-based defense mechanisms. We studied this below-aboveground interaction using a system consisting of lima bean (Phaseolus lunatus L.), rhizobia, and the Mexican bean beetle (Epilachna varivestis Muls.) as an insect herbivore. We showed that the rhizobial symbiosis not only promotes plant growth but also improves plant defense and resistance against herbivores. Results of our study lead to the suggestion that nitrogen provided by rhizobia is allocated to the production of nitrogen-containing cyanogenic defense compounds, and thereby crucially determines the outcome of plant-herbivore interactions. Our study supports the view that the fitness benefit of root symbioses includes defence mechanisms and thus extends beyond the promotion of plant growth. Since the associations between legumes and nitrogen-fixing rhizobia are ubiquitous in terrestrial ecosystems, improved knowledge on rhizobia-mediated effects on plant traits-and the resulting effects on higher trophic levels-is important for better understanding of the role of these microbes for ecosystem functioning.

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Nodulation of white clover (Trifolium repens) in the absence ofRhizobium

Cited by 31 publications

References 14 publications

Nod Factors Induce Nod Factor Cleaving Enzymes in Pea Roots. Genetic and Pharmacological Approaches Indicate Different Activation Mechanisms

Nod Factors Induce Nod Factor Cleaving Enzymes in Pea Roots. Genetic and Pharmacological Approaches Indicate Different Activation Mechanisms

Autoregulation of nodulation (AON) in Pisum sativum (pea) involves signalling events associated with both nodule primordia development and nitrogen fixation

Dual benefit from a belowground symbiosis: nitrogen fixing rhizobia promote growth and defense against a specialist herbivore in a cyanogenic plant

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