A modified aeroponic system for growing small-seeded legumes and other plants to study root systems (original) (raw)
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Plant Methods
Background Root and tuber crops are becoming more important for their high source of carbohydrates, next to cereals. Despite their commercial impact, there are significant knowledge gaps about the environmental and inherent regulation of storage root (SR) differentiation, due in part to the innate problems of studying storage roots and the lack of a suitable model system for monitoring storage root growth. The research presented here aimed to develop a reliable, low-cost effective system that enables the study of the factors influencing cassava storage root initiation and development. Results We explored simple, low-cost systems for the study of storage root biology. An aeroponics system described here is ideal for real-time monitoring of storage root development (SRD), and this was further validated using hormone studies. Our aeroponics-based auxin studies revealed that storage root initiation and development are adaptive responses, which are significantly enhanced by the exogenous...
Floriculture, Ornamental and Plant Biotechnology: Advances and Topical Issues Vol. III, 2006
Legumes have the unique capacity to interact symbiotically with rhizobia, with the formation of root nodules as a result, in which nitrogen fixation takes place. The microsymbionts offer the plant an unlimited nitrogen source by fixing atmospheric nitrogen in the newly developed organs. Because of their symbiotic nitrogen fixation capacity and the accumulation of high protein levels in their seeds, legume crops are of major importance in a sustainable ecological agriculture. Medicago truncatula and Lotus japonicus are the model legume systems for the scientific community to study the biological features of indeterminate and determinate root nodulation, respectively, but also to investigate the improvement of grain legumes. Comparative genome and syntenic studies are currently performed, resulting in a potential new tool to extend the knowledge of the model legumes to agriculturally important crops, such as soybean, alfalfa and pea. The biological and molecular researches are mainly accomplished thanks to recent advances in biotechnological techniques with newly developed tools, such as genome analysis, bioinformatics, transcriptomics, proteomics and metabolomics. The knowledge of the signaling pathways leading to nodulation could eventually result in the nodulation of non-legume crops. In this chapter, major findings are discussed with the aim at providing the reader with a clear overview of the latest insights into the legume-Rhizobium nodulation field.
Regulation of legume nodulation by acidic growth conditions
Plant Signaling & Behavior, 2013
The Development and Regulation of Legume Nodulation Many legumes have evolved to establish a symbiosis with nitrogen-fixing soil-bacteria collectively known as rhizobia (including the genera Azorhizobium, Allorhizobium, Bradyrhizobium, Mesorhizobium, Rhizobium and Sinorhizobium). Rhizobia invade the roots of compatible legume plants leading to the development of specialized root structures called nodules. 1-4 Within these nodules, the nitrogenase enzyme complex of rhizobia reduces atmospheric nitrogen, an unusable form of nitrogen for plants, into ammonia, which the plant utilizes for growth and development. 5,6 Nodule formation and nitrogen fixation are energy expensive and are therefore tightly regulated to ensure a balance between nitrogen acquisition and energy expenditure. One internal control mechanism of the plant is the Autoregulation of Nodulation (AON), a regulatory process acting via long distance signaling. 1-3,7-9 AON is initiated during early nodule development by the production of a rhizobia-induced signal in the root, which is mobilised to the shoot. 10 In soybean, GmRIC1 and GmRIC2 of the CLAVATA3/ESR-related (CLE) family of peptides, have
The article has been written in view of the importance attached to symbiotic N2-fixation taking place in unique organs called legume root nodules under tropics and subtropics. Nodules on legume roots are formed in interaction with soil bacteria a and b rhizobia. Symbiotic interactions between compatible legume host plant and rhizobia involve a fine tuned, molecular communication between the two partners. Calcium has been reported to playa crucial role in symbiotic signaling. Nod factors are central to the initial establishment of legume -rhizobial symbiosis. Production of these signaling molecules is activated by the release of plant phenolics, mainly flavonoids, in the rhizosphere, where they induce a set of nod genes in the appropriate rhizobial strain, leading to synthesis of Nod factors. The nature of both flavonoid signal from plant and Nod factor from the microbial partner are central to the maintenance of specificity in this symbiosis, ensuring that plant accommodates only the useful bacterium. Generally the invasion of plant root occurs through an invagination of root hair cell, called infection thread, at the primary site of interaction. The infection thread spans through the entire root cortex allowing rhizobial invasion into dividing cells of nodule primordium. Rhizobia are released from infection thread into membrane enclosed compartments, where they convert from free living form to N2-fixing form named the bacteroids. Development of functional nodules requires differentiation of both plant and microbial cells. Transcriptomics and proteomics reveal truly great extent of plant and microbial differentiation. Symbiotic N2-fixation is a finely regulated process that involves carbon and energy metabolism of the host plant significantly. The process is also under regulation by N-feedback and °2 supply within the nodules. Redox balance and antioxidant defense system play important roles in establishment of legume-rhizobial symbiosis as well as nodule functioning. Longevity and N2-fixing efficiency of nodules are hugely dependent on environmental conditions prevailing in tropical and subtropical conditions.
Frontiers in Plant Science, 2018
Members of the plant family Leguminosae (Fabaceae) are unique in that they have evolved a symbiotic relationship with rhizobia (a group of soil bacteria that can fix atmospheric nitrogen). Rhizobia infect and form root nodules on their specific host plants before differentiating into bacteroids, the symbiotic form of rhizobia. This complex relationship involves the supply of C 4-dicarboxylate and phosphate by the host plants to the microsymbionts that utilize them in the energy-intensive process of fixing atmospheric nitrogen into ammonium, which is in turn made available to the host plants as a source of nitrogen, a macronutrient for growth. Although nitrogen-fixing bacteroids are no longer growing, they are metabolically active. The symbiotic process is complex and tightly regulated by both the host plants and the bacteroids. The metabolic pathways of carbon, nitrogen, and phosphate are heavily regulated in the host plants, as they need to strike a fine balance between satisfying their own needs as well as those of the microsymbionts. A network of transporters for the various metabolites are responsible for the trafficking of these essential molecules between the two partners through the symbiosome membrane (plant-derived membrane surrounding the bacteroid), and these are in turn regulated by various transcription factors that control their expressions under different environmental conditions. Understanding this complex process of symbiotic nitrogen fixation is vital in promoting sustainable agriculture and enhancing soil fertility.
Nodular diagnosis for ecological engineering of the symbiotic nitrogen fixation with legumes
Procedia Environmental Sciences, 2011
As a major contributor to the reduced nitrogen pool in the biosphere, symbiotic nitrogen fixation by legumes plays a critical role in a sustainable production system. However this legume contribution varies with the physico-chemical and biological conditions of the nodulated-root rhizosphere. In order to assess the abiotic and biotic constrains that might limit this symbiosis at the agroecosystem level, a nodular diagnosis is proposed with common bean as a model grain-legume, and a major source of plant proteins for world human nutrition. The engineering of the legume symbiosis is addressed by participatory assessment of bean recombinant inbred lines contrasting for their efficiency in use of phosphorous for symbiotic nitrogen fixation. With this methodology, in field-sites chosen with farmers of an area of cereal-cropping in the Mediterranean basin, a large spatial and temporal variation in the legume nodulation was found. Soil P availability was a major limiting factor of the rhizobial symbiosis. In order to relate the field measurements with progress in functional genomics of the symbiosis, in situ RT-PCR on nodule sections has been implemented showing that the phytase gene is expressed in the cortex with significantly higher number of transcripts in P-efficient RILs. It is concluded that various tools and indicators are available for developing the ecological engineering of the rhizobial symbiosis, in particular for its beneficial contribution to the bio-geochemical cycle of N, and also P and C.
2016
La culture de Légumineuses présente le double intérêt de permettre une production de graines à haute valeur nutritionnelle sans nécessité d’un apport d’engrais azoté. La nutrition azotée des légumineuses dépend en effet majoritairement de la fixation symbiotique de l’azote atmosphérique réalisée par des bactéries du sol, les rhizobia, au sein des nodosités, et dans une moindre mesure, de l’assimilation de l’azote minéral du sol par les racines.Une meilleure compréhension a été acquise sur le contrôle génétique de la mise en place des racines et des nodosités et sur leur impact sur la nutrition azotée. Une grande variabilité génétique pour ces caractères a été mise en évidence, ainsi que l’existence de corrélations génétiques entre eux. Une approche de génétique quantitative a permis d’identifier des régions génomiques pouvant être impliquées dans leurs variations. Deux pistes d’amélioration de la nutrition azotée ont aussi été étudiées : l’amélioration de l’acquisition d’azote par l...
Doklady biological sciences : proceedings of the Academy of Sciences of the USSR, Biological sciences sections / translated from Russian
Symbiotic nitrogen fixation is the most efficient, environmentally friendly, and inexpensive means of providing plants with "biological nitrogen." It is exemplified by legume-rhizobium characterized by compartmentalization of diazotrophic bacteria in special structures, root nodules . A way to spread this method of providing plants with "biological nitrogen" to nonleguminous plants is paranodulation, where nodule-like structures ( p -nodules) are artificially induced on the roots of nonleguminous plants with various nodulation agents, both abiogenic and biogenic , and then inoculated with diazotrophic bacteria.