Project

evolution; leaf senescence; seed maturation; pathway diversity; chlorophyll breakdown; phyllobilin

Lead
Lead: Das Projekt untersucht biochemische, molekulare und evolutionäre Aspekte des Chlorophyllabbaus, der während der Blattalterung und Fruchtreife in Pflanzen auftritt.
Lay summary
Während der Blattalterung und der Reifung von vielen Früchten bauen Pflanzen Chlorophyll zu einer Klasse von linearen tetrapyrrolischen Stoffen, sogenannten Phyllobilinen, ab. Der Abbau von Chlorophyll beinhaltet eine komplexe Reihe von biochemischen Reaktionen, die man in zwei Abschnitte einteilen kann, und erfordert den zellulären Transport der Phyllobiline vom Chloroplasten zur Vakuole. Obwohl die meisten der am Chlorophyllabbau beteiligten Enzyme in den letzten Jahren molekular identifiziert werden konnten, bestehen offene Fragen in Bezug auf (i) einige enzymatische Schritte des zweiten Teils des Abbauweges, (ii) Modulationen des Abbaus in unterschiedlichen Geweben einer Pflanze, (iii) den Grad der Variabilität des Abbaus innerhalb der Angiospermen und (iv) den evolutionären Ursprung und die phylogenetische Diversität der Enzyme des Abbaus. Das Ziel dieses Projekts ist es, diese Fragen zu klären.

Direct link to Lay Summary

Last update: 16.06.2017

Active participation

Communication	Title	Media	Place	Year

Number	Title	Start	Funding scheme

The so-called PAO/phyllobilin pathway of chlorophyll breakdown consists of two parts. First, chlorophyll is converted to a primary fluorescent chlorophyll catabolite (pFCC) with PHEOPHORBIDE A OXYGENASE (PAO) as the key enzyme. In the second part, pFCC is modified by different enzymes to ultimately produce a species-specific variety of final chlorophyll degradation products, so-called phyllobilins, which accumulate in the vacuole of senescent cells. Phyllobilins have been identified from more than twenty angiosperm species, mostly in senescent leaves. Accordingly, it has been considered that the PAO/phyllobilin pathway is highly conserved within higher plants. Even though almost all enzymatic steps of the first part of the PAO/phyllobilin pathway have been elucidated in the past, there are open questions regarding (i) the conservation of the pathway in different tissues within a given species, (ii) the degree of pathway diversity among different angiosperm species, including the molecular identity of several phyllobilin-modifying enzymes, and (iii) the evolutionary origin and phylogenetic distribution and diversity of the enzymes of the pathway. This proposal aims to address some of these aspects by answering the following questions:- How can tissue-specific differences in phyllobilin formation be explained?- How diverse is the occurrence of phyllobilins within photosynthetic organisms?- How widely distributed and how similar are the enzymes that catalyze PAO/phyllobilin pathway reactions?- What is the molecular identity of so far unknown activities within the pathway?To answer these questions, a variety of molecular, biochemical and analytical methods will be used. These include (i) analysis of enzyme activities, (ii) classical protein purification, (iii) production of transgenic plants by classical T-DNA- and CRISPR/Cas9-based methods and their analysis, (iv) phyllobilin analysis by liquid chromatography-mass spectrometry, (v) genome-wide association studies and (vi) bioinformatics- and proteomics-based identification of candidate proteins.Breakdown of chlorophyll is a physiological process that has a broad impact for daily life; among other aspects it is relevant for the food industry, for example the shelf life of leafy vegetables and fruits, and for the amenity sector, for example turf grass systems. With this in mind, it seems surprising that the mechanism of chlorophyll breakdown so far mainly focused on a few angiosperm model species. This proposal aims to get a better picture about the extent of existence and variability of the PAO/phyllobilin pathway within the lineage of oxygenic photosynthetic organisms and about its evolutionary origin.