China
Africa
Explore chapters and articles related to this topic
Nodulin Function and Nodulin Gene Regulation in Root Nodule Development
Published in Peter M. Gresshoff, Molecular Biology of Symbiotic Nitrogen Fixation, 2018
A unique feature of root nodule development, as opposed to other plant developmental processes, is the involvement of a prokaryote in the induction and control of development. The regulatory role of Rhizobium offers unique possibilities for dissecting this plant differentiation process. Moreover, it offers an entry to the elucidation of the signals that guide root nodule development by allowing the identification of the Rhizobium genes responsible for these signals. An amazingly limited number of bacterial genes, the nod genes, appear to generate the signal(s) for the induction of early nodulin gene expression. The same genes are also in some way involved in the induction of late nodulin gene expression. Elucidation of the nature and mode of action of the signals involved will contribute to our understanding of root nodule development. Also by virtue of the relative ease of manipulation of the inducing Rhizobium, root nodule development is a highly attractive system for the study of plant developmental biology, apart from the intrinsic fascination of symbiotic nitrogen fixation.
The Normal and The Pathological
Published in Lawrie Reznek, The Nature of Disease, 1987
The assumption here seems to be that it is because root nodules have the nature of a tumour that they are pathological (induced by pathogens). However, this is fallacious. It is not the case that the root nodule is pathological simply because it is a tumour - that is, because of its nature. It is not pathological because it is beneficial (and not harmful) to the plant.
Insights in nodule-inhabiting plant growth promoting bacteria and their ability to stimulate Vicia faba growth
Published in Egyptian Journal of Basic and Applied Sciences, 2022
Amr M. Mowafy, Mona S. Agha, Samia A. Haroun, Mohamed A. Abbas, Mohamed Elbalkini
Symbiotic nitrogen fixation, which is positioned as a major part of biological nitrogen fixation, is an important alternative source of chemical nitrogen fertilizers not only for leguminous but also for non-leguminous plants. The interaction between legumes and rhizobia leads to root nodule organogenesis, an organ that is produced in response to bacterial nod factors and plant developmental signals leading to the formation of a plant stem cell niche [1]. Recently, rhizobia have been shown to improve the nutrition of non-leguminous crops, such as barley, wheat and canola [2]. It has been established that the legume nodule is exclusively inhabited by the rhizobium. Meanwhile, in 2001, this concept has changed dramatically when non-rhizobial strains were regarded for their ability to nodulate legumes, such as Methylobacterium and Burkholderia that have been isolated from Crotalaria [3] and Mimosa [4], respectively. In addition to nodule-inducing bacteria, several bacterial strains have been isolated from nodules as co-inhabitants with rhizobium, such as Klebsiella, Pseudomonas [5], Bacillus [6] and Streptomyces [7]. Interestingly, a review titled ‘the nodule microbiome: N2-fixing rhizobia do not live alone’ has been published in 2017 to conclude that some of these non-rhizobial bacteria might be nitrogen fixer or participate in nodule genesis and the others, more striking, might neither participate in nodulation nor fix nitrogen [8].
Nanotoxicity of engineered nanomaterials (ENMs) to environmentally relevant beneficial soil bacteria – a critical review
Published in Nanotoxicology, 2019
Ricky W. Lewis, Paul M. Bertsch, David H. McNear
A full review of the effects of ENM exposure on plant–microbe interactions is beyond the scope of this review; however, it is useful to provide highlights of what is currently known regarding N-fixing microsymbionts in the context of their host plants. There is relatively little known concerning the influence of ENM on root nodule development or function. From an environmental protection perspective, the most relevant study to date examined the physiological responses of Medicago truncatula A17 grown in Si. meliloti Rm 2011 inoculated soils amended with field composted biosolids containing Ag, ZnO, and TiO2 ENMs or AgNO3, ZnSO4, and micron-sized TiO2 (Judy, McNear, et al. 2015). In this study, the ENM-enriched biosolids significantly reduced the number of root nodules (<1 nodule/plant) observed after 30 d of growth compared with the no metal control and the dissolved/bulk enriched biosolids amended treatment, which had 4–6 nodules/plant, respectively. This effect did not appear to be a result of enhanced plant health, as ENM treatment significantly decreased fresh shoot biomass (32%), dried root biomass (35%), and shoot length (19%). There was a reduction in Si. meliloti CFU estimates by bulk/dissolved and ENM treatments (90 and 86% reduction, respectively); however, reduced nodulation did not appear to be a result of decreased survival of Si. meliloti in the ENM treatments, as nodulation was not influenced by bulk/dissolved treatments. Regardless, it remains unclear if ENM-specific stress responses may have influenced Si. meliloti physiology, thereby reducing the symbiotic capacity of the organism. The authors suggest that enhanced zinc uptake observed in the ENM treatments likely explains much of the observed responses, but further research is required because plants were co-exposed to several metals at once. Furthermore, additional experiments should be duplicated using biosolids from multiple sources with varying compositions to determine the influence of biosolid specific factors.