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Host-specific Nod-factors associated with Medicago truncatula nodule infection differentially induce calcium influx and calcium spiking in root hairs.

ABSTRACT: Rhizobial nodulation (Nod) factors activate both nodule morphogenesis and infection thread development during legume nodulation. Nod factors induce two different calcium responses: intra-nuclear calcium oscillations and a calcium influx at the root hair tip. Calcium oscillations activate nodule development; we wanted to test if the calcium influx is associated with infection. Sinorhizobium meliloti nodL and nodF mutations additively reduce infection of Medicago truncatula. Nod-factors made by the nodL mutant lack an acetyl group; mutation of nodF causes the nitrogen (N)-linked C16:2 acyl chain to be replaced by C18:1. We tested whether these Nod-factors differentially induced calcium influx and calcium spiking. The absence of the NodL-determined acetyl group greatly reduced the induction of calcium influx without affecting calcium spiking. The calcium influx was even further reduced if the N-linked C16:2 acyl group was replaced by C18:1. These additive effects on calcium influx correlate with the additive effects of mutations in nodF and nodL on legume infection. Infection thread development is inhibited by ethylene, which also inhibited Nod-factor-induced calcium influx. We conclude that Nod-factor perception differentially activates the two developmental pathways required for nodulation and that activation of the pathway involving the calcium influx is important for efficient infection.

SUBMITTER: Morieri G

PROVIDER: S-EPMC3908372 | biostudies-literature | 2013 Nov

REPOSITORIES: biostudies-literature

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Host-specific Nod-factors associated with Medicago truncatula nodule infection differentially induce calcium influx and calcium spiking in root hairs.

Morieri Giulia G Martinez Eduardo A EA Jarynowski Andrzej A Driguez Hugues H Morris Richard R Oldroyd Giles E D GED Downie J Allan JA

The New phytologist 20130910 3

Rhizobial nodulation (Nod) factors activate both nodule morphogenesis and infection thread development during legume nodulation. Nod factors induce two different calcium responses: intra-nuclear calcium oscillations and a calcium influx at the root hair tip. Calcium oscillations activate nodule development; we wanted to test if the calcium influx is associated with infection. Sinorhizobium meliloti nodL and nodF mutations additively reduce infection of Medicago truncatula. Nod-factors made by th ...[more]

PMID: 24015832

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Project description:BackgroundThe formation of functional symbiotic nodules is the result of a coordinated developmental program between legumes and rhizobial bacteria. Genetic analyses in legumes have been used to dissect the signaling processes required for establishing the legume-rhizobial endosymbiotic association. Compared to the early events of the symbiotic interaction, less attention has been paid to plant loci required for rhizobial colonization and the functioning of the nodule. Here we describe the identification and characterization of a number of new genetic loci in Medicago truncatula that are required for the development of effective nitrogen fixing nodules.ResultsApproximately 38,000 EMS and fast neutron mutagenized Medicago truncatula seedlings were screened for defects in symbiotic nitrogen fixation. Mutant plants impaired in nodule development and efficient nitrogen fixation were selected for further genetic and phenotypic analysis. Nine mutants completely lacking in nodule formation (Nod-) represented six complementation groups of which two novel loci have been identified. Eight mutants with ineffective nodules (Fix-) represented seven complementation groups, out of which five were new monogenic loci. The Fix- M. truncatula mutants showed symptoms of nitrogen deficiency and developed small white nodules. Microscopic analysis of Fix- nodules revealed that the mutants have defects in the release of rhizobia from infection threads, differentiation of rhizobia and maintenance of persistence of bacteria in nodule cells. Additionally, we monitored the transcriptional activity of symbiosis specific genes to define what transcriptional stage of the symbiotic process is blocked in each of the Fix- mutants. Based on the phenotypic and gene expression analysis a functional hierarchy of the FIX genes is proposed.ConclusionsThe new symbiotic loci of M. truncatula isolated in this study provide the foundation for further characterization of the mechanisms underpinning nodulation, in particular the later stages associated with bacterial release and nodule function.

Dataset Information

Host-specific Nod-factors associated with Medicago truncatula nodule infection differentially induce calcium influx and calcium spiking in root hairs.

Publications

Host-specific Nod-factors associated with Medicago truncatula nodule infection differentially induce calcium influx and calcium spiking in root hairs.

Similar Datasets

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