scholarly journals Rhizobia Can Induce Nodules in White Clover by “Hijacking” Mature Cortical Cells Activated During Lateral Root Development

2000 ◽  
Vol 13 (2) ◽  
pp. 170-182 ◽  
Author(s):  
Ulrike Mathesius ◽  
Jeremy J. Weinman ◽  
Barry G. Rolfe ◽  
Michael A. Djordjevic
Keyword(s):  
Lateral Root ◽  
Chalcone Synthase ◽  
Root Hairs ◽  
Gus Expression ◽  
Flavonoid Compound ◽  
Nodule Formation ◽  
Cortical Cells ◽  
Lateral Root Development ◽  
Bacterial Genes ◽  
Mature Root

We examined a range of responses of root cortical cells to Rhizobium sp. inoculation to investigate why rhizobia preferentially nodulate legume roots in the zone of emerging root hairs, but generally fail to nodulate the mature root. We tested whether the inability to form nodules in the mature root is due to a lack of plant flavonoids to induce the bacterial genes required for nodulation or a failure of mature cortical cells to respond to Rhizobium spp. When rhizobia were inoculated in the zone of emerging root hairs, changes in β-glucuronidase (GUS) expression from an auxin-responsive promoter (GH3), expression from three chalcone synthase promoters, and the accumulation of specific flavonoid compounds occurred in cortical cells prior to nodule formation. Rhizobia failed to induce these responses when inoculated in the mature root, even when co-inoculated with nod gene-inducing flavonoids. However, mature root hairs remained responsive to rhizobia and could support infection thread formation. This suggests that a deficiency in signal transduction is the reason for nodulation failure in the mature root. However, nodules could be initiated in the mature root at sites of lateral root emergence. A comparison between lateral root and nodule formation showed that similar patterns of GH3:gusA expression, chalcone synthase gene expression, and accumulation of a particular flavonoid compound occurred in the cortical cells involved in both processes. The results suggest that rhizobia can“ hijack” cortical cells next to lateral root emergence sites because some of the early responses required for nodule formation have already been activated by the plant in those cells.

scholarly journals Auxin: at the root of nodule development?

2008 ◽  
Vol 35 (8) ◽  
pp. 651 ◽  
Author(s):  
Ulrike Mathesius
Keyword(s):  
Lateral Root ◽  
De Novo ◽  
Root Nodules ◽  
Lateral Roots ◽  
Nodule Development ◽  
Nodule Formation ◽  
Cortical Cells ◽  
Lateral Root Development ◽  
Organ Differentiation ◽  
Development And Differentiation

Root nodules are formed as a result of an orchestrated exchange of chemical signals between symbiotic nitrogen fixing bacteria and certain plants. In plants that form nodules in symbiosis with actinorhizal bacteria, nodules are derived from lateral roots. In most legumes, nodules are formed de novo from pericycle and cortical cells that are re-stimulated for division and differentiation by rhizobia. The ability of plants to nodulate has only evolved recently and it has, therefore, been suggested that nodule development is likely to have co-opted existing mechanisms for development and differentiation from lateral root formation. Auxin is an important regulator of cell division and differentiation, and changes in auxin accumulation and transport are essential for lateral root development. There is growing evidence that rhizobia alter the root auxin balance as a prerequisite for nodule formation, and that nodule numbers are regulated by shoot-to-root auxin transport. Whereas auxin requirements appear to be similar for lateral root and nodule primordium activation and organ differentiation, the major difference between the two developmental programs lies in the specification of founder cells. It is suggested that differing ratios of auxin and cytokinin are likely to specify the precursors of the different root organs.

A shared gene drives lateral root development and root nodule symbiosis pathways in Lotus

Science ◽  
2019 ◽  
Vol 366 (6468) ◽  
pp. 1021-1023 ◽  
Author(s):  
Takashi Soyano ◽  
Yoshikazu Shimoda ◽  
Masayoshi Kawaguchi ◽  
Makoto Hayashi
Keyword(s):  
Root Development ◽  
Lateral Root ◽  
Root Nodule ◽  
Root Nodules ◽  
Lotus Japonicus ◽  
Cortical Cell ◽  
Cortical Cells ◽  
Lateral Root Development ◽  
Lateral Organ ◽  
Nodule Symbiosis

Legumes develop root nodules in symbiosis with nitrogen-fixing rhizobial bacteria. Rhizobia evoke cell division of differentiated cortical cells into root nodule primordia for accommodating bacterial symbionts. In this study, we show that NODULE INCEPTION (NIN), a transcription factor in Lotus japonicus that is essential for initiating cortical cell divisions during nodulation, regulates the gene ASYMMETRIC LEAVES 2-LIKE18/LATERAL ORGAN BOUNDARIES DOMAIN16a (ASL18/LBD16a). Orthologs of ASL18/LBD16a in nonlegume plants are required for lateral root development. Coexpression of ASL18a and the CCAAT box–binding protein Nuclear Factor-Y (NF-Y) subunits, which are also directly targeted by NIN, partially suppressed the nodulation-defective phenotype of L. japonicusdaphne mutants, in which cortical expression of NIN was attenuated. Our results demonstrate that ASL18a and NF-Y together regulate nodule organogenesis. Thus, a lateral root developmental pathway is incorporated downstream of NIN to drive nodule symbiosis.

Ontogeny of Alnus rubra – Alpova diplophloeus ectomycorrhizae. I. Light microscopy and scanning electron microscopy

1989 ◽  
Vol 67 (1) ◽  
pp. 191-200 ◽  
Author(s):  
H. B. Massicotte ◽  
R. L. Peterson ◽  
L. H. Melville
Keyword(s):  
Outer Layer ◽  
Lateral Root ◽  
Lateral Roots ◽  
Root Hairs ◽  
Fungal Colonization ◽  
Alnus Rubra ◽  
Cortical Cells ◽  
Lateral Root Primordia ◽  
Hartig Net ◽  
Fungal Hyphae

Ectomycorrhizae synthesized between Alpova diplophloeus and Alnus rubra are of two morphological types: one with a mantle formed along the entire length of the lateral roots and the other, the clavate type, with the mantle confined to the apical portion of the laterals. The morphology of the mycorrhiza is dependent on the stage of lateral root elongation at the time of colonization by fungal hyphae. Clavate mycorrhizae form on lateral roots that have already elongated at the time of fungal colonization. Fungal hyphae interact with root hairs at the base of clavate mycorrhizae. Mantles of both types are fairly compact with few extramatrical hyphae. Hartig net hyphae, which branch profusely primarily in the radial direction, are confined to the epidermis and midway along the radial walls of the outer layer of cortical cells. Second-order lateral root primordia are initiated in the mature Hartig net zone. Cells in the outer layer of the cortex of mycorrhizal roots collapse during fixation, indicating the possible presence of a barrier in the cell wall blocking the ingress of fixative.

Prenodule formation and primary nodule development in roots of Comptonia (Myricaceae)

1977 ◽  
Vol 55 (17) ◽  
pp. 2306-2318 ◽  
Author(s):  
Dale Callaham ◽  
John G. Torrey
Keyword(s):  
Root Hair ◽  
Lateral Root ◽  
Lateral Roots ◽  
Cortical Cell ◽  
Host Cells ◽  
Nodule Development ◽  
Nodule Formation ◽  
Cortical Cells ◽  
Lateral Root Primordium ◽  
Root Primordium

Seedlings of the sweet fern, Comptonia peregrina (L.) Coult., grown aeroponically, were inoculated with a nodule suspension to allow infection by the actinomycete-like organism which causes nodule formation. Roots with early stages of infection and nodule initiation were fixed, embedded in resin, sectioned, and examined. Infection is infrequent in Comptonia with only a few nodules per seedling root system. Infection via root hair invasion causes the retention of the curled and deformed root hair in an intensely cytoplasmic state with ramification of multiple filamentous strands of the endophyte. A limited cortical proliferation occurs in response to the infection forming the prenodule; endophyte filaments grow radially inward from the base of the infected epidermal root hair and invade a portion of the prenodular cells resulting in their hypertrophy. Distal and proximal to the prenodule site, a number of primary nodule primordia are initiated, varying from a few up to a dozen or more. These primordia appear to develop more or less simultaneously under the stimulus of the invading endophyte; they are like lateral roots in their site of origin, occurring largely opposite the protoxylem poles and involving pericyclic and endodermal cell proliferation. They differ in that the cortical cells external to each primordium are stimulated to undergo divisions and these cortical cell derivatives are incorporated into the developing primordium. The endophyte enters the cortical tissues of the lateral root on which the prenodule has formed and then invades proximal and distal to the infection site, progressing into the cortical tissues of each of the developing nodule primordia. A cork-like layer develops on the original lateral root in areas not occupied by primordia by initiation of subepidermal cell divisions and wall thickening. Normal lateral root primordium formation occurs in the pericycle opposite the protoxylem poles and involves cellular derivatives of the pericycle and endodermis but no cortical cells, which instead are crushed and displaced by the lateral root primordium as it develops. Nodule formation clearly involves complex chemical interactions, which remain for further study, between the host cells and the invading endophyte.

scholarly journals High throughput phenotyping of root growth dynamics, lateral root formation, root architecture and root hair development enabled by PlaRoM

2009 ◽  
Vol 36 (11) ◽  
pp. 938 ◽  
Author(s):  
Nima Yazdanbakhsh ◽  
Joachim Fisahn
Keyword(s):  
Root Growth ◽  
Growth Kinetics ◽  
Lateral Root ◽  
Root Architecture ◽  
Imaging Techniques ◽  
Plant Root ◽  
Primary Root ◽  
Growth Media ◽  
Root Extension ◽  
Lateral Root Development

Plant organ phenotyping by non-invasive video imaging techniques provides a powerful tool to assess physiological traits and biomass production. We describe here a range of applications of a recently developed plant root monitoring platform (PlaRoM). PlaRoM consists of an imaging platform and a root extension profiling software application. This platform has been developed for multi parallel recordings of root growth phenotypes of up to 50 individual seedlings over several days, with high spatial and temporal resolution. PlaRoM can investigate root extension profiles of different genotypes in various growth conditions (e.g. light protocol, temperature, growth media). In particular, we present primary root growth kinetics that was collected over several days. Furthermore, addition of 0.01% sucrose to the growth medium provided sufficient carbohydrates to maintain reduced growth rates in extended nights. Further analysis of records obtained from the imaging platform revealed that lateral root development exhibits similar growth kinetics to the primary root, but that root hairs develop in a faster rate. The compatibility of PlaRoM with currently accessible software packages for studying root architecture will be discussed. We are aiming for a global application of our collected root images to analytical tools provided in remote locations.

Lateral root formation and nutrients: nitrogen in the spotlight

2021 ◽  
Author(s):  
Pierre-Mathieu Pélissier ◽  
Hans Motte ◽  
Tom Beeckman
Keyword(s):  
Signaling Pathways ◽  
Root System ◽  
Root Development ◽  
Lateral Root ◽  
Molecular Mechanisms ◽  
Root Formation ◽  
Lateral Roots ◽  
Nutrient Use Efficiency ◽  
Lateral Root Formation ◽  
Lateral Root Development

Abstract Lateral roots are important to forage for nutrients due to their ability to increase the uptake area of a root system. Hence, it comes as no surprise that lateral root formation is affected by nutrients or nutrient starvation, and as such contributes to the root system plasticity. Understanding the molecular mechanisms regulating root adaptation dynamics towards nutrient availability is useful to optimize plant nutrient use efficiency. There is at present a profound, though still evolving, knowledge on lateral root pathways. Here, we aimed to review the intersection with nutrient signaling pathways to give an update on the regulation of lateral root development by nutrients, with a particular focus on nitrogen. Remarkably, it is for most nutrients not clear how lateral root formation is controlled. Only for nitrogen, one of the most dominant nutrients in the control of lateral root formation, the crosstalk with multiple key signals determining lateral root development is clearly shown. In this update, we first present a general overview of the current knowledge of how nutrients affect lateral root formation, followed by a deeper discussion on how nitrogen signaling pathways act on different lateral root-mediating mechanisms for which multiple recent studies yield insights.

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.

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