Signals and Responses

Lee, Angie; Hirsch, Ann M.

doi:10.4161/psb.1.4.3143

Cited by 26 publications

(11 citation statements)

References 73 publications

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“…As with most other legumes, V. karroo can form nitrogen-fixing root nodules (Barnes, 2001) in mutualistic symbioses with specific soil bacteria referred to as rhizobia (Poole et al, 2018). These bacteria do not form a monophyletic group and are represented by species in 18 genera of the Alpha- and Betaproteobacteria (Lee and Hirsch, 2006; Poole et al, 2018; de Lajudie et al, 2019). To differentiate between rhizobia from these two classes, they are informally referred to as alpha- and beta-rhizobia (Moulin et al, 2001).…”

Section: Introductionmentioning

confidence: 99%

Both Alpha- and Beta-Rhizobia Occupy the Root Nodules of Vachellia karroo in South Africa

et al. 2019

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Vachellia karroo (formerly Acacia karroo ) is a wide-spread legume species indigenous to southern Africa. Little is known regarding the identity or diversity of rhizobia that associate with this plant in its native range in South Africa. The aims of this study were therefore: (i) to gather a collection of rhizobia associated with V. karroo from a wide range of geographic locations and biomes; (ii) to identify the isolates and infer their evolutionary relationships with known rhizobia; (iii) to confirm their nodulation abilities by using them in inoculation assays to induce nodules under glasshouse conditions. To achieve these aims, soil samples were collected from 28 locations in seven biomes throughout South Africa, which were then used to grow V. karroo seedlings under nitrogen-free conditions. The resulting 88 bacterial isolates were identified to genus-level using 16S rRNA sequence analysis and to putative species-level using recA -based phylogenetic analyses. Our results showed that the rhizobial isolates represented members of several genera of Alphaproteobacteria ( Bradyrhizobium , Ensifer , Mesorhizobium , and Rhizobium ), as well as Paraburkholderia from the Betaproteobacteria. Our study therefore greatly increases the known number of Paraburkholderia isolates which can associate with this southern African mimosoid host. We also show for the first time that members of this genus can associate with legumes, not only in the Fynbos biome, but also in the Albany Thicket and Succulent Karoo biomes. Twenty-six putative species were delineated among the 88 isolates, many of which appeared to be new to Science with other likely being conspecific or closely related to E. alkalisoli , M. abyssinicae , M. shonense , and P. tropica . We encountered only a single isolate of Bradyrhizobium , which is in contrast to the dominant association of this genus with Australian Acacia . V. karroo also associates with diverse genera in the Grassland biome where it is quite invasive and involved in bush encroachment. Our findings therefore suggest that V. karroo is a promiscuous host capable of forming effective nodules with both alpha- and beta-rhizobia, which could be a driving force behind the ecological success of this tree species.

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Section: Introductionmentioning

confidence: 99%

Both Alpha- and Beta-Rhizobia Occupy the Root Nodules of Vachellia karroo in South Africa

et al. 2019

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“…The influx of Ca 2+ ions leads to local depolarization of the root hair cell membrane (Felle et al, 1999). Ca 2+ ions interact with cytoplasmic proteins (MtDMI3, PsSYM9) (Lévy et al, 2004;Mitra et al, 2004), which are probably transported to the cell nucleus, where they activate the NSP1 and NSP2 transcription factors in Medicago truncatula (Kaló et al, 2005;Smit et al, 2005;Hirsh et al, 2009), LjNIN in Lotus japonicus (Schauser et al, 1999;Borisov et al, 2003), and PsSYM35 in Pisum sativum (Lee & Hirsh, 2006, Ferguson et al, 2010. In this way, transcription of genes encoding the plant early nodulin proteins (ENODs) is initiated.…”

Section: Perception Of the Nod Factorsmentioning

confidence: 99%

“…These genes encode proteins from the nodulin group (Skøt, 2003). The so-called early nodulins include, among others, ENOD12 and ENOD5 proteins, which are present in root hair cells and in the infection zone of the forming nodules (Lee & Hirsh, 2006). In turn, genes called late nodulins are activated after completion of the nodule morphogenesis and are involved in binding of the atmospheric nitrogen by bacteroids.…”

Section: The Nod Factors Activate Some Plant Genesmentioning

confidence: 99%

Biological activity of Nod factors

et al. 2020

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Chemically, the Nod factors (NFs) are lipochitooligosaccharides, produced mainly by bacteria of the Rhizobium genus. They are the main signaling molecules involved in the initiation of symbiosis between rhizobia and legume plants. Nod factors affect plant tissues at very low concentrations, even as low as 10–12 mol/L. They induce root hair deformation, cortical cell division, and root nodules’ formation in the host plant. At the molecular level, the cytoskeleton is reorganized and expression of genes encoding proteins called nodulins is induced in response to Nod factors in the cell. Action of Nod factors is highly specific because it depends on the structure of a particular Nod factor involved, as well as the plant receptor reacting with it.

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“…Rhizobia are able to switch from their free-living state into an N 2 -fixing symbiotic state inside root and stem nodules of certain legumes [ 17 , 18 , 19 ]. The sequential molecular mechanisms that lead to the infection of the legume and to the differentiation of the bacteria into bacteroids in a mature functional nodule have been studied in detail for alpha-rhizobia [ 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ]. The sequencing and public availability of the complete genomes of several rhizobia and legumes have allowed researchers to develop and apply functional genomics approaches to comprehensively understand how rhizobia reorganize and adapt to new environments, such as the root nodule [ 30 , 31 , 32 , 33 , 34 ].…”

Section: Introductionmentioning

confidence: 99%

Functional Genomics Approaches to Studying Symbioses between Legumes and Nitrogen-Fixing Rhizobia

Lardi

Pessi

2018

High-Throughput

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Biological nitrogen fixation gives legumes a pronounced growth advantage in nitrogen-deprived soils and is of considerable ecological and economic interest. In exchange for reduced atmospheric nitrogen, typically given to the plant in the form of amides or ureides, the legume provides nitrogen-fixing rhizobia with nutrients and highly specialised root structures called nodules. To elucidate the molecular basis underlying physiological adaptations on a genome-wide scale, functional genomics approaches, such as transcriptomics, proteomics, and metabolomics, have been used. This review presents an overview of the different functional genomics approaches that have been performed on rhizobial symbiosis, with a focus on studies investigating the molecular mechanisms used by the bacterial partner to interact with the legume. While rhizobia belonging to the alpha-proteobacterial group (alpha-rhizobia) have been well studied, few studies to date have investigated this process in beta-proteobacteria (beta-rhizobia).

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Signals and Responses

Cited by 26 publications

References 73 publications

Both Alpha- and Beta-Rhizobia Occupy the Root Nodules of Vachellia karroo in South Africa

Both Alpha- and Beta-Rhizobia Occupy the Root Nodules of Vachellia karroo in South Africa

Biological activity of Nod factors

Functional Genomics Approaches to Studying Symbioses between Legumes and Nitrogen-Fixing Rhizobia

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