<i>MtHAP2-1</i> is a key transcriptional regulator of symbiotic nodule development regulated by microRNA169 <i>in Medicago truncatula</i>

Combier, Jean; Frugier, Florian; Billy, Françoise de; Boualem, Adnane; El-Yahyaoui, Fikri; Moreau, Sandra; Vernié, Tatiana; Ott, Thomas; Gamas, Pascal; Crespi, Martín; Niebel, Andréas

doi:10.1101/gad.402806

Cited by 468 publications

(494 citation statements)

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“…In wild-type infections, the DMI2 protein is localized to the infection thread and symbiosome membranes, which is consistent with a role for this protein in release of bacteria from infection threads and symbiosome development 70 . RNAi-mediated knockdown of the MtHAP2-1 gene, which encodes a predicted transcription factor, also prevents bacterial release from infection threads 71 . The M. truncatula nip mutant also produces overgrown infection threads and the bacteria fail to release from these infection threads 72 .…”

Section: Endocytosis Of Rhizobiamentioning

confidence: 99%

How rhizobial symbionts invade plants: the Sinorhizobium–Medicago model

et al. 2007

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Nitrogen-fixing rhizobial bacteria and leguminous plants have evolved complex signal exchange mechanisms that allow a specific bacterial species to induce its host plant to form invasion structures through which the bacteria can enter the plant root. Once the bacteria have been endocytosed within a host-membrane-bound compartment by root cells, the bacteria differentiate into a new form that can convert atmospheric nitrogen into ammonia. Bacterial differentiation and nitrogen fixation are dependent on the microaerobic environment and other support factors provided by the plant. In return, the plant receives nitrogen from the bacteria, which allows it to grow in the absence of an external nitrogen source. Here, we review recent discoveries about the mutual recognition process that allows the model rhizobial symbiont Sinorhizobium meliloti to invade and differentiate inside its host plant alfalfa (Medicago sativa) and the model host plant barrel medic (Medicago truncatula).The recent completion of the Sinorhizobium meliloti genome sequence, and the progress towards the completion of the Medicago truncatula genome sequence, have led to a surge in the molecular characterization of the determinants that are involved in the development of the symbiosis between rhizobial bacteria and leguminous plants. Aromatic compounds from legumes called flavonoids first signal the rhizobial bacteria to produce lipochitooligosaccharide compounds called Nod factors 1 . Nod factors that are secreted by the bacteria activate multiple responses in the host plant that prepare the plant to receive the invading bacteria. Nod factors and symbiotic exopolysaccharides induce the plant to form infection threads, which are thin tubules filled with bacteria that penetrate into the plant cortical tissue and deliver the bacteria to their target cells. Plant cells in the inner cortex internalize the invading bacteria in host-membrane-bound compartments that mature into structures known Correspondence to G.C.W. gwalker@mit.edu. Competing interests statementThe authors declare no competing financial interests. DATABASES Invasion of plant rootsAlthough plant roots are exposed to various micro-organisms in the soil, their cell walls form a strong protective barrier against most harmful species. The early steps in the invasion of barrel medic (M. truncatula) and alfalfa (Medicago sativa) roots by S. meliloti are characterized by the reciprocal exchange of signals that allow the bacteria to use the plant root hair cells as a means of entry. Initial signal exchangeFlavonoid compounds (2-phenyl-1,4-benzopyrone derivatives) produced by leguminous plants are the first signals to be exchanged by host-rhizobial symbiont pairs 1 (FIG. 1). Flavonoids bind bacterial NodD proteins, which are members of the LysR family of transcriptional regulators, and activate these proteins to induce the transcription of rhizobial genes 1,2 . For example, the M. sativa-derived flavonoid luteolin stimulates binding of an active form of NodD1 to an S. meliloti 'nod-box' p...

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Section: Endocytosis Of Rhizobiamentioning

confidence: 99%

How rhizobial symbionts invade plants: the Sinorhizobium–Medicago model

et al. 2007

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“…Indeed, in A. thaliana, miR169 genes show distinct or overlapping expression patterns in all stages of plant development [52]. Hence, the miR169 family diversification in legumes may have led to the generation of miR169 genes that become responsive to nodulation, such as those reported in Combier et al [19]. Interestingly, a deep-sequencing analysis of miRNAs during soybean nodulation revealed a downregulation of miR169 accumulation from 3 h after inoculation of the symbiotic bacteria [38].…”

Section: Conserved Micrornas Regulate Transcription Factors That Arementioning

confidence: 99%

“…In some cases, the miRNA* may even preferentially accumulate compared with the miRNA, suggesting that the choice of the dominant strand of the miRNA may be an effective means to diversify miRNA-mediated gene regulation. In M. truncatula, miR169 regulates the expression of a transcription factor from the CCAAT-binding family (or NFYA), called MtHAP2-1 [19] (table 1). The overexpression of the mtr-miR169a precursor significantly affects nodule development [19].…”

Section: Conserved Micrornas Regulate Transcription Factors That Arementioning

confidence: 99%

“…In M. truncatula, miR169 regulates the expression of a transcription factor from the CCAAT-binding family (or NFYA), called MtHAP2-1 [19] (table 1). The overexpression of the mtr-miR169a precursor significantly affects nodule development [19]. The nodulation process is delayed, and nodule growth is arrested for 8-10 days following inoculation with a concomitant defect in nitrogen-fixing ability.…”

Section: Conserved Micrornas Regulate Transcription Factors That Arementioning

confidence: 99%

“…In recent years, small riboregulators, such as the microRNAs (miRNAs) miR166 and miR169, have been added to the complex signalling pathways that control nodulation, mainly as repressors of key transcription factors [18,19]. In plants, several pathways are known to generate endogenous small non-coding RNAs [20,21], which share common biochemical reactions.…”

Section: Introductionmentioning

confidence: 99%

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Complexity of miRNA-dependent regulation in root symbiosis

Bazin

Bustos-Sanmamed

Hartmann

et al. 2012

Phil. Trans. R. Soc. B

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The development of root systems may be strongly affected by the symbiotic interactions that plants establish with soil organisms. Legumes are able to develop symbiotic relationships with both rhizobial bacteria and arbuscular mycorrhizal fungi leading to the formation of nitrogen-fixing nodules and mycorrhizal arbuscules, respectively. Both of these symbiotic interactions involve complex cellular reprogramming and profound morphological and physiological changes in specific root cells. In addition, the repression of pathogenic defence responses seems to be required for successful symbiotic interactions. Apart from typical regulatory genes, such as transcription factors, microRNAs (miRNAs) are emerging as riboregulators that control gene networks in eukaryotic cells through interactions with specific target mRNAs. In recent years, the availability of deep-sequencing technologies and the development of in silico approaches have allowed for the identification of large sets of miRNAs and their targets in legumes. A number of conserved and legume-specific miRNAs were found to be associated with symbiotic interactions as shown by their expression patterns or actions on symbiosis-related targets. In this review, we combine data from recent literature and genomic and deep-sequencing data on miRNAs controlling nodule development or restricting defence reactions to address the diversity and specificity of miRNA-dependent regulation in legume root symbiosis. Phylogenetic analysis of miRNA isoforms and their potential targets suggests a role for miRNAs in the repression of plant defence during symbiosis and revealed the evolution of miRNA-dependent regulation in legumes to allow for the modification of root cell specification, such as the formation of mycorrhized roots and nitrogen-fixing nodules.

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Plant Hormones and Initiation of Legume Nodulation and Arbuscular Mycorrhization

Mukherjee¹

2011

Ecological Aspects of Nitrogen Metabolism in Plants

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MtHAP2-1 is a key transcriptional regulator of symbiotic nodule development regulated by microRNA169 in Medicago truncatula

Cited by 468 publications

References 28 publications

How rhizobial symbionts invade plants: the Sinorhizobium–Medicago model

How rhizobial symbionts invade plants: the Sinorhizobium–Medicago model

Complexity of miRNA-dependent regulation in root symbiosis

Plant Hormones and Initiation of Legume Nodulation and Arbuscular Mycorrhization

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