scholarly journals Plant genes involved in root-nodule development on legumes

1995 ◽  
Vol 350 (1331) ◽  
pp. 101-107 ◽  
Keyword(s):  
Root Nodule ◽  
Nodule Development ◽  
Nodule Formation ◽  
Atmospheric Nitrogen ◽  
Cortical Cells ◽  
Nod Factor ◽  
Plant Genes ◽  
Thread Formation ◽  
Nodulin Genes ◽  
Infection Thread Formation

Rhizobium is able to induce the formation of a new organ on roots of leguminous plants, the root nodule, in which the penetrated bacteria fix atmospheric nitrogen. This process is initiated by specific lipo-oligosaccharides, called Nod factors, secreted by the bacterium. Nodule formation proceeds through distinct steps like infection thread formation and activation of mitotic activity in cortical cells. During these steps specific plant genes, nodulin genes, are induced and several of these have been identified and characterized. Nodulin genes are used now as markers to study Nod factor perception and signal transduction.

scholarly journals The Ethylene Responsive Factor Required for Nodulation 1 (ERN1) Transcription Factor Is Required for Infection-Thread Formation in Lotus japonicus

2017 ◽  
Vol 30 (3) ◽  
pp. 194-204 ◽  
Author(s):  
Yasuyuki Kawaharada ◽  
Euan K. James ◽  
Simon Kelly ◽  
Niels Sandal ◽  
Jens Stougaard
Keyword(s):  
Transcription Factor ◽  
Root Nodule ◽  
Lotus Japonicus ◽  
Epidermal Cells ◽  
Infection Thread ◽  
Nod Factor ◽  
Infection Threads ◽  
Thread Formation ◽  
Ethylene Responsive Factor ◽  
Infection Thread Formation

Several hundred genes are transcriptionally regulated during infection-thread formation and development of nitrogen-fixing root nodules. We have characterized a set of Lotus japonicus mutants impaired in root-nodule formation and found that the causative gene, Ern1, encodes a protein with a characteristic APETALA2/Ethylene Responsive Factor (AP2/ERF) transcription-factor domain. Phenotypic characterization of four ern1 alleles shows that infection pockets are formed but root-hair infection threads are absent. Formation of root-nodule primordia is delayed and no normal transcellular infection threads are found in the infected nodules. Corroborating the role of ERN1 (ERF Required for Nodulation1) in nodule organogenesis, spontaneous nodulation induced by an autoactive CCaMK and cytokinin–induced nodule primordia were not observed in ern1 mutants. Expression of Ern1 is induced in the susceptible zone by Nod factor treatment or rhizobial inoculation. At the cellular level, the pErn1:GUS reporter is highly expressed in root epidermal cells of the susceptible zone and in the cortical cells that form nodule primordia. The genetic regulation of this cellular expression pattern was further investigated in symbiotic mutants. Nod factor induction of Ern1 in epidermal cells was found to depend on Nfr1, Cyclops, and Nsp2 but was independent of Nin and Nf-ya1. These results suggest that ERN1 functions as a transcriptional regulator involved in the formation of infection threads and development of nodule primordia and may coordinate these two processes.

scholarly journals The Mesorhizobium loti purB Gene Is Involved in Infection Thread Formation and Nodule Development in Lotus japonicus

2007 ◽  
Vol 189 (22) ◽  
pp. 8347-8352 ◽  
Author(s):  
Shin Okazaki ◽  
Yoshiyuki Hattori ◽  
Kazuhiko Saeki
Keyword(s):  
Lotus Japonicus ◽  
Infection Thread ◽  
Nodule Development ◽  
Nodule Formation ◽  
Mesorhizobium Loti ◽  
Infection Threads ◽  
Thread Formation ◽  
Infection Thread Formation

ABSTRACT The purB and purH mutants of Mesorhizobium loti exhibited purine auxotrophy and nodulation deficiency on Lotus japonicus. In the presence of adenine, only the purH mutant induced nodule formation and the purB mutant produced few infection threads, suggesting that 5-aminoimidazole-4-carboxamide ribonucleotide biosynthesis catalyzed by PurB is required for the establishment of symbiosis.

Root nodule development: origin, function and regulation of nodulin genes

1992 ◽  
Vol 85 (2) ◽  
pp. 253-265 ◽  
Author(s):  
D. P. S. Verma ◽  
C.-A. Hu ◽  
M. Zhang
Keyword(s):  
Root Nodule ◽  
Nodule Development ◽  
Origin Function ◽  
Nodulin Genes

Effects of a Nod-factor-overproducing strain of Sinorhizobium meliloti on the expression of the ENOD40 gene in Melilotus alba

2002 ◽  
Vol 80 (9) ◽  
pp. 907-915 ◽  
Author(s):  
Walter F Giordano ◽  
Michelle R Lum ◽  
Ann M Hirsch
Keyword(s):  
Lateral Root ◽  
Sinorhizobium Meliloti ◽  
Cortical Cell ◽  
Host Cells ◽  
Nodule Development ◽  
Nodule Formation ◽  
Additional Increase ◽  
Nod Factor ◽  
Melilotus Alba ◽  
Different Strains

We have initiated studies on the molecular biology and genetics of white sweetclover (Melilotus alba Desr.) and its responses to inoculation with the nitrogen-fixing symbiont Sinorhizobium meliloti. Early nodulin genes such as ENOD40 serve as markers for the transition from root to nodule development even before visible stages of nodule formation are evident. Using Northern blot analysis, we found that the ENOD40 gene was expressed within 6 h after inoculation with two different strains of S. meliloti, one of which overproduces symbiotic Nod factors. Inoculation with this strain resulted in an additional increase in ENOD40 gene expression over a typical wild-type S. meliloti strain. Moreover, the increase in mRNA brought about by the Nod-factor-overproducing strain 24 h after inoculation was correlated with lateral root formation by using whole-mount in situ hybridization to localize ENOD40 transcripts in lateral root meristems and by counting lateral root initiation sites. Cortical cell divisions were not detected. We also found that nodulation occurred more rapidly on white sweetclover in response to the Nod-factor-overproducing strain, but ultimately there was no difference in nodulation efficiency in terms of nodule number or the number of roots nodulated by the two strains. Also, the two strains could effectively co-colonize the host when inoculated together, although a few host cells were occupied by both strains.Key words: ENOD40, Nod factor, Melilotus, Sinorhizobium, symbiosis.

scholarly journals Phosphate Deficiency Negatively Affects Early Steps of the Symbiosis between Common Bean and Rhizobia

2018 ◽  
Author(s):  
Mariel C Isidra-Arellano ◽  
María del Rocio Reyero-Saavedra ◽  
María del Socorro Sánchez-Correa ◽  
Lise Pingault ◽  
Sidharth Sen ◽  
...  
Keyword(s):  
Common Bean ◽  
Transcriptional Analysis ◽  
Phosphate Deficiency ◽  
Nodule Formation ◽  
Significant Progress ◽  
Thread Formation ◽  
Pi Deficiency ◽  
Genetic Responses ◽  
Shed Light ◽  
Infection Thread Formation

Phosphate (Pi) deficiency reduces nodule formation and development in different legume species including common bean. Despite the significant progress in the understanding of the genetic responses underlying the adaptation of nodules to Pi deficiency, it is still unclear whether this nutritional deficiency interferes with the molecular dialog between legumes and rhizobia, if so, what part of the molecular dialog is impaired? In this study, we provide evidence demonstrating that Pi deficiency negatively affects critical early molecular and physiological responses required for a successful symbiosis between common bean and rhizobia. We demonstrated that the infection thread formation and the expression of PvNSP2, PvNIN, and PvFLOT2, genes controlling the nodulation process, were significantly reduced in Pi-deficient common bean seedlings. Further transcriptional analysis revealed that the expression of hormones-related genes is compromised in Pi-deficient seedlings inoculated with rhizobia. Additionally, we showed that regardless of the presence or absence of rhizobia, the expression of PvRIC1 and PvRIC2, two genes participating in the autoregulation of nodule number, was higher in Pi-deficient seedlings than in control seedlings. The data presented in this study shed light on the understanding of how Pi deficiency impacts the early steps of the symbiosis between common bean and rhizobia.

scholarly journals Spontaneous Root-Nodule Formation in the Model Legume Lotus japonicus: A Novel Class of Mutants Nodulates in the Absence of Rhizobia

2006 ◽  
Vol 19 (4) ◽  
pp. 373-382 ◽  
Author(s):  
Leïla Tirichine ◽  
Euan K. James ◽  
Niels Sandal ◽  
Jens Stougaard
Keyword(s):  
Root Nodule ◽  
Lotus Japonicus ◽  
Nodule Development ◽  
Nodule Formation ◽  
Wild Type ◽  
Model Legume ◽  
Isolation And Characterization ◽  
Mutant Lines ◽  
Spontaneous Nodules

Root-nodule development in legumes is an inducible developmental process initially triggered by perception of lipochitin-oligosaccharide signals secreted by the bacterial microsymbiont. In nature, rhizobial colonization and invasion of the legume root is therefore a prerequisite for formation of nitrogen-fixing root nodules. Here, we report isolation and characterization of chemically induced spontaneously nodulating mutants in a model legume amenable to molecular genetics. Six mutant lines of Lotus japonicus were identified in a screen for spontaneous nodule development under axenic conditions, i.e., in the absence of rhizobia. Spontaneous nodules do not contain rhizobia, bacteroids, or infection threads. Phenotypically, they resemble ineffective white nodules formed by some bacterial mutants on wild-type plants or certain plant mutants inoculated with wild-type Mesorhizobium loti. Spontaneous nodules formed on mutant lines show the ontogeny and characteristic histological features described for rhizobia-induced nodules on wild-type plants. Physiological responses to nitrate and ethylene are also maintained, as elevated levels inhibit spontaneous nodulation. Activation of the nodule developmental program in spontaneous nodules was shown for the early nodulin genes Enod2 and Nin, which are both upregulated in spontaneous nodules as well as in rhizobial nodules. Both monogenic recessive and dominant spontaneous nodule formation (snf) mutations were isolated in this mutant screen, and map positions were determined for three loci. We suggest that future molecular characterization of these mutants will identify key plant determinants involved in regulating nodulation and provide new insight into plant organ development.

scholarly journals Enhanced Nodulation and Nodule Development by nolR Mutants of Sinorhizobium medicae on Specific Medicago Host Genotypes

2014 ◽  
Vol 27 (4) ◽  
pp. 328-335 ◽  
Author(s):  
Masayuki Sugawara ◽  
Michael J. Sadowsky
Keyword(s):  
Sinorhizobium Meliloti ◽  
Regulatory Protein ◽  
Selective Advantage ◽  
Nodule Development ◽  
Nodule Formation ◽  
Wild Type ◽  
Nod Factor ◽  
Transcriptional Regulatory ◽  
Sinorhizobium Medicae ◽  
Nodule Initiation

The nolR gene encodes a negatively acting, transcriptional regulatory protein of core Nod-factor biosynthetic genes in the sinorhizobia. Although previous reports showed that nolR modulates Nod-factor production and enhances nodulation speed of Sinorhizobium meliloti on alfalfa, there have been no reports for the symbiotic function of this gene in the S. medicae–Medicago truncatula symbiosis. Here, we constructed an nolR mutant of S. medicae WSM419 and evaluated mutant and wild-type strains for their nodulation ability, competitiveness, host specificity, and density-dependent nodulation phenotypes. When the mutant was inoculated at low and medium population densities, it showed enhanced nodule formation during the initial stages of nodulation. Results of quantitative competitive nodulation assays indicated that an nolR mutant had 2.3-fold greater competitiveness for nodulation on M. truncatula ‘A17’ than did the wild-type strain. Moreover, the nodulation phenotype of the nolR mutant differed among Medicago genotypes and showed significantly enhanced nodule development on M. tricycla. Taken together, these results indicated that mutation of nolR in S. medicae positively influenced nodule initiation, competitive nodulation, and nodule development at later nodulation stages. This may allow nolR mutants of S. medicae to have a selective advantage under field conditions.

Determinate development of nodule roots in actinomycete-induced root nodules of Myrica gale

1978 ◽  
Vol 56 (11) ◽  
pp. 1357-1364 ◽  
Author(s):  
John G. Torrey ◽  
Dale Callaham
Keyword(s):  
Root Development ◽  
Root Nodules ◽  
Cortical Cell ◽  
Gas Diffusion ◽  
Nodule Development ◽  
Nodule Formation ◽  
Low Oxygen ◽  
Cortical Cells ◽  
Continuous Growth ◽  
Myrica Gale

Young seedlings of Myrica gale L. grown in water culture were inoculated with a nodule suspension containing the effective actinomycete which induced root nodule formation. Nodule development was followed from initiation to nodule lobe formation and nodule root development using living materials and fixed nodules sectioned for light microscopy. After root hair infection and prenodule formation, three stages were observed: nodule lobe formation, a transition or arrested state, and nodule root development. The primary nodule lobe meristem originates endogenously and its formation involves pericycle, endodermis, and cortical cell derivatives. The lobe develops slowly to about 2 mm in length while the cortical cells are invaded by the actinomycete endophyte. After a period of arrest of variable duration, from a few days to several weeks, the nodule lobe meristem begins altered development, forming the elongate nodule root which undergoes slow but continuous growth to about 3- to 4-cm final length. New nodule lobe primordia are initiated endogenously at the base of existing nodules lobes, ultimately forming a cluster of nodule roots. Each nodule root, which elongates at about 0.1–1.0 mm per day, has a terminal apical meristem with reduced root cap formation and produces a modified root structure possessing an elaborate cortical intercellular space system and a reduced central cylinder. Nodule root growth is distinctive in that it shows strong negative geotropism. The endophyte is restricted to cortical cells of the nodule lobe and is totally absent from tissues of the nodule root. A probable role for nodule roots is to facilitate gas diffusion to the nitrogen-fixing endophyte site in the nodule lobe when nodules occur under conditions of low oxygen tension.

scholarly journals Identification of Bradyrhizobium elkanii USDA61 Type III Effectors Determining Symbiosis with Vigna mungo

Genes ◽  
2020 ◽  
Vol 11 (5) ◽  
pp. 474 ◽  
Author(s):  
Hien P. Nguyen ◽  
Safirah T. N. Ratu ◽  
Michiko Yasuda ◽  
Neung Teaumroong ◽  
Shin Okazaki
Keyword(s):  
Type Iii Secretion ◽  
Phylogenetic Analyses ◽  
Vigna Mungo ◽  
Nod Factor ◽  
Type Iii Effectors ◽  
Type Iii ◽  
Effector Genes ◽  
Thread Formation ◽  
Bradyrhizobium Elkanii ◽  
Infection Thread Formation

Bradyrhizobium elkanii USDA61 possesses a functional type III secretion system (T3SS) that controls host-specific symbioses with legumes. Here, we demonstrated that B. elkanii T3SS is essential for the nodulation of several southern Asiatic Vigna mungo cultivars. Strikingly, inactivation of either Nod factor synthesis or T3SS in B. elkanii abolished nodulation of the V. mungo plants. Among the effectors, NopL was identified as a key determinant for T3SS-dependent symbiosis. Mutations of other effector genes, such as innB, nopP2, and bel2-5, also impacted symbiotic effectiveness, depending on host genotypes. The nopL deletion mutant formed no nodules on V. mungo, but infection thread formation was still maintained, thereby suggesting its pivotal role in nodule organogenesis. Phylogenetic analyses revealed that NopL was exclusively conserved among Bradyrhizobium and Sinorhizobium (Ensifer) species and showed a different phylogenetic lineage from T3SS. These findings suggest that V. mungo evolved a unique symbiotic signaling cascade that requires both NFs and T3Es (NopL).

Sign in / Sign up

Export Citation Format

Share Document