A Novel Ankyrin-Repeat Membrane Protein, IGN1, Is Required for Persistence of Nitrogen-Fixing Symbiosis in Root Nodules of <i>Lotus japonicus</i>

Kumagai, Hirotaka; Hakoyama, Tomoyuki; Umehara, Yosuke; Sato, Shusei; Kaneko, Takakazu; Tabata, Satoshi; Kouchi, Hiroshi

doi:10.1104/pp.106.095356

Cited by 78 publications

(77 citation statements)

References 62 publications

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“…5D). Such early senescence of symbiotic cells is commonly found in Fix Ϫ plant mutants (28,34,38,39,67). The senescence process generally brings about rupture of the symbiosome membrane, breakdown of the bacteroid, and autolysis of the plant cell cytosol (59).…”

Section: Resultsmentioning

confidence: 99%

Involvement of the Azorhizobial Chromosome Partition Gene ( parA ) in the Onset of Bacteroid Differentiation during Sesbania rostrata Stem Nodule Development

Liu¹,

Lee²,

Wang³

et al. 2011

Appl Environ Microbiol

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A parA gene in-frame deletion mutant of Azorhizobium caulinodans ORS571 (ORS571-⌬parA) was constructed to evaluate the roles of the chromosome-partitioning gene on various bacterial traits and on the development of stem-positioned nodules. The ⌬parA mutant showed a pleiomorphic cell shape phenotype and was polyploid, with differences in nucleoid sizes due to dramatic defects in chromosome partitioning. Upon inoculation of the ⌬parA mutant onto the stem of Sesbania rostrata, three types of immature nodule-like structures with impaired nitrogen-fixing activity were generated. Most showed signs of bacteroid early senescence. Moreover, the ⌬parA cells within the nodule-like structures exhibited multiple developmental-stage phenotypes. Since the bacA gene has been considered an indicator for bacteroid formation, we applied the expression pattern of bacA as a nodule maturity index in this study. Our data indicate that the bacA gene expression is parA dependent in symbiosis. The presence of the parA gene transcript was inversely correlated with the maturity of nodule; the transcript was switched off in fully mature bacteroids. In summary, our experimental evidence demonstrates that the parA gene not only plays crucial roles in cellular development when the microbe is free-living but also negatively regulates bacteroid formation in S. rostrata stem nodules.

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Section: Resultsmentioning

confidence: 99%

Involvement of the Azorhizobial Chromosome Partition Gene ( parA ) in the Onset of Bacteroid Differentiation during Sesbania rostrata Stem Nodule Development

Liu¹,

Lee²,

Wang³

et al. 2011

Appl Environ Microbiol

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show abstract

“…proportion of ern2 nodules (Hossain et al, 2006;Kumagai et al, 2007;Pislariu et al, 2012;Bourcy et al, 2013;Berrabah et al, 2014). It has also been suggested that nodule senescence can be triggered by the host to avoid the energetic cost of maintaining ineffective nodules (Suganuma et al, 2003;Magori and Kawaguchi, 2009).…”

Section: Mild Infection Defects May Contribute To the Accelerated Senmentioning

confidence: 99%

The Symbiosis-Related ERN Transcription Factors Act in Concert to Coordinate Rhizobial Host Root Infection

et al. 2016

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Legumes improve their mineral nutrition through nitrogen-fixing root nodule symbioses with soil rhizobia. Rhizobial infection of legumes is regulated by a number of transcription factors, including ERF Required for Nodulation1 (ERN1). Medicago truncatula plants defective in ERN1 are unable to nodulate, but still exhibit early symbiotic responses including rhizobial infection. ERN1 has a close homolog, ERN2, which shows partially overlapping expression patterns. Here we show that ern2 mutants exhibit a later nodulation phenotype than ern1, being able to form nodules but with signs of premature senescence. Molecular characterization of the ern2-1 mutation reveals a key role for a conserved threonine for both DNA binding and transcriptional activity. In contrast to either single mutant, the double ern1-1 ern2-1 line is completely unable to initiate infection or nodule development. The strong ern1-1 ern2-1 phenotype demonstrates functional redundancy between these two transcriptional regulators and reveals the essential role of ERN1/ERN2 to coordinately induce rhizobial infection and nodule organogenesis. While ERN1/ERN2 act in concert in the root epidermis, only ERN1 can efficiently allow the development of mature nodules in the cortex, probably through an independent pathway. Together, these findings reveal the key roles that ERN1/ERN2 play at the very earliest stages of root nodule development.

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“…This mutant, named enhanced nitrogen fixation1 (enf1), exhibits enhanced symbiotic nitrogen fixation activity. Most legume nitrogen fixation activity mutants, such as ineffective greenish nodules1 (ign1), stationary endosymbiont nodule1, and symbiotic sulfate transporter1 (sst1), are Fix 2 (Suganuma et al, 2003;Krusell et al, 2005;Kumagai et al, 2007).…”

mentioning

confidence: 99%

Enhanced Nodulation and Nitrogen Fixation in the Abscisic Acid Low-Sensitive Mutant enhanced nitrogen fixation1 of Lotus japonicus

et al. 2009

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The phytohormone abscisic acid (ABA) is known to be a negative regulator of legume root nodule formation. By screening Lotus japonicus seedlings for survival on an agar medium containing 70 mM ABA, we obtained mutants that not only showed increased root nodule number but also enhanced nitrogen fixation. The mutant was designated enhanced nitrogen fixation1 (enf1) and was confirmed to be monogenic and incompletely dominant. The low sensitivity to ABA phenotype was thought to result from either a decrease in the concentration of the plant's endogenous ABA or from a disruption in ABA signaling. We determined that the endogenous ABA concentration of enf1 was lower than that of wild-type seedlings, and furthermore, when wild-type plants were treated with abamine, a specific inhibitor of 9-cis-epoxycarotenoid dioxygenase, which results in reduced ABA content, the nitrogen fixation activity of abamine-treated plants was elevated to the same levels as enf1. We also determined that production of nitric oxide in enf1 nodules was decreased. We conclude that endogenous ABA concentration not only regulates nodulation but also nitrogen fixation activity by decreasing nitric oxide production in nodules.

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A Novel Ankyrin-Repeat Membrane Protein, IGN1, Is Required for Persistence of Nitrogen-Fixing Symbiosis in Root Nodules of Lotus japonicus

Cited by 78 publications

References 62 publications

Involvement of the Azorhizobial Chromosome Partition Gene ( parA ) in the Onset of Bacteroid Differentiation during Sesbania rostrata Stem Nodule Development

Involvement of the Azorhizobial Chromosome Partition Gene ( parA ) in the Onset of Bacteroid Differentiation during Sesbania rostrata Stem Nodule Development

The Symbiosis-Related ERN Transcription Factors Act in Concert to Coordinate Rhizobial Host Root Infection

Enhanced Nodulation and Nitrogen Fixation in the Abscisic Acid Low-Sensitive Mutant enhanced nitrogen fixation1 of Lotus japonicus

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