ORCID Profile
0000-0001-9057-2392
Current Organisation
Wageningen University
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Publisher: Cold Spring Harbor Laboratory
Date: 03-12-2022
DOI: 10.1101/2022.12.03.518951
Abstract: Development of symbiotic root nodules is a cytokinin-dependent process that is critical to nitrogen acquisition in legumes. The extent and manner in which root nodules contribute to whole-plant cytokinin and nitrogen supply signalling is unknown. Using a combination of genetic, biochemical and physiological approaches, we characterised the role of cytokinin synthesis, export and perception in coordination of symbiotic nodule development and shoot growth in the legume Lotus japonicus . LjPup1 encodes a plasma membrane localised cytokinin exporter with isopentenyladenine (iP) and trans -Zeatin (tZ) export capacity. LjPup1 shows a distinct nodule-specific expression pattern with greatest transcript levels detected in mature nodules. Mutants accumulate more isopentenyladenine riboside (iPR) in nodule tissues and demonstrate hallmarks of reduced cytokinin signalling. Despite normal nodule numbers and function, shoot growth is markedly reduced in Ljpup1 mutants, as well as in mutants impaired in tZ biosynthesis. We found symbiotic root nodules contribute to shoot growth via export of active cytokinins. A cytokinin exporter in the purine permease family thus contributes to long-distance cytokinin homeostasis regulating plant development.
Publisher: Cold Spring Harbor Laboratory
Date: 04-11-2020
DOI: 10.1101/2020.11.03.366971
Abstract: Legumes balance nitrogen acquisition from soil nitrate with symbiotic nitrogen fixation. Nitrogen fixation requires establishment of a new organ, which is a cytokinin dependent developmental process in the root. We found cytokinin biosynthesis is a central integrator, balancing nitrate signalling with symbiotic acquired nitrogen. Low nitrate conditions provide a permissive state for induction of cytokinin by symbiotic signalling and thus nodule development. In contrast, high nitrate is inhibitory to cytokinin accumulation and nodule establishment in the root zone susceptible to nodule formation. This reduction of symbiotic cytokinin accumulation was further exacerbated in cytokinin biosynthesis mutants, which display hypersensitivity to nitrate inhibition of nodule development, maturation and nitrogen fixation. Consistent with this, cytokinin application can rescue nodulation and nitrogen fixation of biosynthesis mutants in a concentration dependent manner. These inhibitory impacts of nitrate on symbiosis occur in a Nlp1 and Nlp4 dependent manner and contrast with the positive influence of nitrate on cytokinin biosynthesis that occurs in non-symbiotic species. Altogether this shows that legumes, as exemplified by Lotus japonicus , have evolved a different cytokinin response to nitrate compared to non-legumes. Cytokinin biosynthesis is suppressed by nitrate in Lotus japonicus , providing a mechanism for nitrate inhibition of symbiotic nodule organogenesis.
Publisher: Springer Science and Business Media LLC
Date: 11-11-2021
DOI: 10.1038/S41467-021-26820-9
Abstract: Legumes balance nitrogen acquisition from soil nitrate with symbiotic nitrogen fixation. Nitrogen fixation requires establishment of a new organ, which is a cytokinin dependent developmental process in the root. We found cytokinin biosynthesis is a central integrator, balancing nitrate signalling with symbiotic acquired nitrogen. Low nitrate conditions provide a permissive state for induction of cytokinin by symbiotic signalling and thus nodule development. In contrast, high nitrate is inhibitory to cytokinin accumulation and nodule establishment in the root zone susceptible to nodule formation. This reduction of symbiotic cytokinin accumulation was further exacerbated in cytokinin biosynthesis mutants, which display hypersensitivity to nitrate inhibition of nodule development, maturation and nitrogen fixation. Consistent with this, cytokinin application rescues nodulation and nitrogen fixation of biosynthesis mutants in a concentration dependent manner. These inhibitory impacts of nitrate on symbiosis occur in a Nlp1 and Nlp4 dependent manner and contrast with the positive influence of nitrate on cytokinin biosynthesis that occurs in species that do not form symbiotic root nodules. Altogether this shows that legumes, as exemplified by Lotus japonicus , have evolved a different cytokinin response to nitrate compared to non-legumes.
No related grants have been discovered for Wouter Kohlen.