Geschmack ist vorhersagbar: Mit FlavorMiner. FlavorMiner heißt das Tool, das IPB-Chemiker und Partner aus Kolumbien jüngst entwickelt haben. Das Programm kann, basierend auf maschinellem Lernen (KI), anhand der…
Seit Februar 2021 bietet Wolfgang Brandt, ehemaliger Leiter der Arbeitsgruppe Computerchemie am IPB, sein Citizen Science-Projekt zur Pilzbestimmung an. Dafür hat er in regelmäßigen Abständen öffentliche Vorträge zur Vielfalt…
Stauder, R.; Welsch, R.; Camagna, M.; Kohlen, W.; Balcke, G. U.; Tissier, A.; Walter, M. H.;Strigolactone Levels in Dicot Roots Are Determined by an Ancestral Symbiosis-Regulated Clade of the PHYTOENE SYNTHASE Gene FamilyFront. Plant Sci.9255(2018)DOI: 10.3389/fpls.2018.00255
Strigolactones (SLs) are apocarotenoid phytohormones synthesized from carotenoid precursors. They are produced most abundantly in roots for exudation into the rhizosphere to cope with mineral nutrient starvation through support of root symbionts. Abscisic acid (ABA) is another apocarotenoid phytohormone synthesized in roots, which is involved in responses to abiotic stress. Typically low carotenoid levels in roots raise the issue of precursor supply for the biosynthesis of these two apocarotenoids in this organ. Increased ABA levels upon abiotic stress in Poaceae roots are known to be supported by a particular isoform of phytoene synthase (PSY), catalyzing the rate-limiting step in carotenogenesis. Here we report on novel PSY3 isogenes from Medicago truncatula (MtPSY3) and Solanum lycopersicum (SlPSY3) strongly expressed exclusively upon root interaction with symbiotic arbuscular mycorrhizal (AM) fungi and moderately in response to phosphate starvation. They belong to a widespread clade of conserved PSYs restricted to dicots (dPSY3) distinct from the Poaceae-PSY3s involved in ABA formation. An ancient origin of dPSY3s and a potential co-evolution with the AM symbiosis is discussed in the context of PSY evolution. Knockdown of MtPSY3 in hairy roots of M. truncatula strongly reduced SL and AM-induced C13 α-ionol/C14 mycorradicin apocarotenoids. Inhibition of the reaction subsequent to phytoene synthesis revealed strongly elevated levels of phytoene indicating induced flux through the carotenoid pathway in roots upon mycorrhization. dPSY3 isogenes are coregulated with upstream isogenes and downstream carotenoid cleavage steps toward SLs (D27, CCD7, CCD8) suggesting a combined carotenoid/apocarotenoid pathway, which provides “just in time”-delivery of precursors for apocarotenoid formation.
Publikation
Walter, M. H.; Stauder, R.; Tissier, A.;Evolution of root-specific carotenoid precursor pathways for apocarotenoid signal biogenesisPlant Sci.2331-10(2015)DOI: 10.1016/j.plantsci.2014.12.017
Various cleavage products of C40 carotenoid substrates are formed preferentially or exclusively in roots. Such apocarotenoid signaling or regulatory compounds differentially induced in roots during environmental stress responses including root colonization by arbuscular mycorrhizal fungi include ABA, strigolactones and C13 α-ionol/C14 mycorradicin derivatives. The low carotenoid levels in roots raise the question of whether there is a regulated precursor supply channeled into apocarotenoid formation distinct from default carotenoid pathways. This review describes root-specific isogene components of carotenoid pathways toward apocarotenoid formation, highlighting a new PSY3 class of phytoene synthase genes in dicots. It is clearly distinct from the monocot PSY3 class co-regulated with ABA formation. At least two members of the exclusive dicot PSY3s are regulated by nutrient stress and mycorrhization. This newly recognized dicot PSY3 (dPSY3 vs. mPSY3 from monocots) class probably represents an ancestral branch in the evolution of the plant phytoene synthase family. The evolutionary history of PSY genes is compared with the evolution of MEP pathway isogenes encoding 1-deoxy-d-xylulose 5-phosphate synthases (DXS), particularly DXS2, which is co-regulated with dPSY3s in mycorrhizal roots. Such stress-inducible isoforms for rate-limiting steps in root carotenogenesis might be components of multi-enzyme complexes committed to apocarotenoid rather than to carotenoid formation.
Publikation
López-Ráez, J. A.; Fernandez, I.; García, J. M.; Berrio, E.; Bonfante, P.; Walter, M. H.; Pozo, M. J.;Differential spatio-temporal expression of carotenoid cleavage dioxygenases regulates apocarotenoid fluxes during AM symbiosisPlant Sci.23059-69(2014)DOI: 10.1016/j.plantsci.2014.10.010
Apocarotenoids are a class of compounds that play important roles in nature. In recent years, a prominent role for these compounds in arbuscular mycorrhizal (AM) symbiosis has been shown. They are derived from carotenoids by the action of the carotenoid cleavage dioxygenase (CCD) enzyme family. In the present study, using tomato as a model, the spatio-temporal expression pattern of the CCD genes during AM symbiosis establishment and functioning was investigated. In addition, the levels of the apocarotenoids strigolactones (SLs), C13 α-ionol and C14 mycorradicin (C13/C14) derivatives were analyzed. The results suggest an increase in SLs promoted by the presence of the AM fungus at the early stages of the interaction, which correlated with an induction of the SL biosynthesis gene SlCCD7. At later stages, induction of SlCCD7 and SlCCD1 expression in arbusculated cells promoted the production of C13/C14 apocarotenoid derivatives. We show here that the biosynthesis of apocarotenoids during AM symbiosis is finely regulated throughout the entire process at the gene expression level, and that CCD7 constitutes a key player in this regulation. Once the symbiosis is established, apocarotenoid flux would be turned towards the production of C13/C14 derivatives, thus reducing SL biosynthesis and maintaining a functional symbiosis.
Bücher und Buchkapitel
Walter, M. H.;Role of Carotenoid Metabolism in the Arbuscular Mycorrhizal Symbiosisde Bruijn, F. J., ed.513-524(2013)ISBN:9781118297674DOI: 10.1002/9781118297674.ch48
Cleavage products of carotenoids (apocarotenoids) exert a variety of often poorly characterized functions in roots and in rhizospheric interactions of plants with both symbionts and parasites. They are generated by regiospecific cleavage enzymes (CCDs, NCEDs) that act in a single or sequential way on C40 carotenoids. Among such apocarotenoids are one well‐known phytohormone controlling drought stress response networks (abscisic acid, ABA) and a newly discovered class of growth regulators involved in adaptive reactions to nutrient stress (strigolactones, SL). A third class of apocarotenoids consists of derivatives of a cyclic cyclohexenone (CH) and a linear mycorradicin (MR) type. They accumulate abundantly as part of a so‐called yellow pigment complex in roots colonized by arbuscular mycorrhizal (AM) fungi. Mycorrhizal phenotypes of pathway knockdown and loss‐of‐function mutants are reviewed in order to clarify the role of the three apocarotenoid classes for the AM symbiosis. One case of pathway interconnection between SL and CH/MR biogenesis through CCD7 is discussed along with other implications for interplay between pathways. SLs appear to preferentially affect early steps of root colonization by AM fungi and thus colonization levels. In contrast, accumulation of CH/MR derivatives is associated with arbuscule formation. Arbuscules are transient structures, which undergo constant degradation and reformation (turnover). Colocalization of CH/MR derivatives with degrading arbuscules and other observations suggest a phytoalexin‐like function in a plant‐controlled degradation of degenerating or poorly functional arbuscules. A model is presented, which proposes maintenance of high levels of functional arbuscules delivering phosphate through plant management of their rapid turnover.