ACTA BIOLOGICA CRACOVIENSIA

BIOSYNTHESIS, GENETICS, AND METABOLISM OF CAROTENOIDS
INVITED LECTURES
New insights into strigolactones biosynthesis
Salim Al-Babili, Adrian Alder
Department of Cell Biology, Faculty of Biology, Albert-Ludwigs
University of Freiburg, Schaenzlestr. 1, 79104 Freiburg, Germany,
salim.albabili@biologie.uni-freiburg.de
Strigolactones (SLs) are isoprenoids with a typical C 19 -structure
consisting of a tricyclic lactone (ABC-rings) connected via an enol
ether bridge to a further lactone, a butenolide group (D-ring). SLs
act as phytohormones regulating plant architecture, in addition to
their role as chemical signals involved in plant-plant and plantfungi
interactions. It was proposed that the synthesis of SLs is initiated
through a carotenoid cleavage step yielding a C 15 -aldehyde
subjected to a series of reactions leading to the ABC C 14 -skeleton,
which is then coupled to a butenolide group of unknown origin.
Plant branching mutants indicated the involvement of the
carotenoid cleavage dioxygenases (CCD) 7 and 8 in the SLs
biosynthesis, and it was supposed that these enzymes catalyze a
sequential cleavage leading to β-apo-13-carotenone (C 18 ) which
structure has little in common with that of SLs. Our study provides
evidence that the activities of CCD7 and 8 are sufficient surpass
the gap between carotenoids and SLs. Using in vitro assays
performed with enzymes from different plant species, we show
that combined CCD7/8 catalysis leads to a product similar to SLs
in its structure and biological activity. The formation of the SLlike
compound indicates that CCD8 catalyzes a series of reactions
including isomerization, Baeyer-Villiger-like rearrangement and
repeated dioxygenation.
Regulation of carotenoid biosynthesis:
impacts on plant development
Christopher I. Cazzonelli, Barry J. Pogson
Centre of Excellence in Plant Energy Biology, Research School of
Biology, The Australian National University,
Building 41 Linnaeus Way, 0200, Canberra, Australia,
christopher.cazzonelli@anu.edu.au
In plants, carotenoids are required for photosynthesis, photoprotection
and the biosynthesis of at least two hormones, namely
abscisic acid and strigolactones. The carotenoid biosynthetic
pathway bifurcates after lycopene to produce lutein or betacarotenes
and its derivatives. Thus the branch point modulates
which carotenoids accumulate [1]. We have shown how the
branch point can be regulated by a chromatin-modifying histone
methyltransferase, Set Domain Group 8, (SDG8), targeting the
carotenoid isomerase (CRTISO) [2]. SDG8 controls the permissive
expression of a small number of genes by histone methylation
of lysine 4 and/or 36 of chromatin surrounding key gene targets
such as CRTISO [3]. Regions within the CRTISO promoter
are required for SDG8 recruitment as well as function, and tissue
specific expression of CRTISO is similar to that of SDG8 [4]. We
are exploring the molecular nature by which SDG8 regulates
CRTISO and how modulating carotenoid flux through the pathway
may perturb the production of carotenoid-derived signaling
molecules. The chromatin modifying nature of SDG8 and novel
functions for CRTISO in regulating plant development have
opened a new door to improve our understanding of epigenetic
processes.
Vol. 53, suppl. 1, 2011
17–22 July 2011, Krakow, Poland
REFERENCES
CAZZONELLI CI and POGSON BJ. 2010. A balance between source and
sink: regulation of carotenoid composition in plants. Trends in
Plant Science 15: 266-274.
CAZZONELLI CI, CUTTRISS AJ, COSSETTO SB, PYE W, CRISP P, WHELAN J,
FINNEGAN J, TURNBULL C, POGSON BJ. 2009. Regulation of
carotenoid composition and shoot branching in Arabidopsis by a
chromatin modifying histone methyltransferase, SDG8. Plant
Cell 21:39-53.
CAZZONELLI CI, MILLAR T, FINNEGAN J and POGSON, BJ. 2009. Promoting
gene expression in plants by permissive histone lysine methylation.
Plant Signaling & Behavior 4:484-488.
CAZZONELLI CI, ROBERTS A, CARMODY M and POGSON BJ. 2010.
Transcriptional Control of Set domain Group8 and Carotenoid
Isomerase During Arabidopsis Development. Molecular Plant 3:
174-191.
Carotenoid biosynthesis in tomato at the
crossroad between genomics and metabolic
engineering
Giovanni Giuliano
ENEA, Casaccia Res Ctr, Via Anguillarese 301, 00123 Roma, Italy,
giovanni.giuliano@enea.it
Tomato (S. lycopersicum) is the second most important horticultural
crop worldwide, a model system for fleshy fruit development,
and the genetically best-characterized plant after
Arabidopsis and maize. Together with S. pimpinellifolium, its
closest wild progenitor, accumulates the unusual carotene,
lycopene, in its fruits. A large number of mutants, affected specifically
in fruit carotenoid biosynthesis, are available, thanks to
widespread gene duplication in the biosynthetic pathway. My lab
has been interested, since the 1990's, in metabolic engineering in
tomato and potato and, more recently, in the genomics of the
pathway in the two plants. The topics touched upon in my talk
will be:
a) the regulatory relations between carotenoid genes and
metabolites in tomato fruits, as revealed by metabolically
engineered plants and mutants
b) the structure and regulation of the carotenoid pathway genes
in tomato and its wild progenitor species
c) the likely molecular events that resulted in the emergence of
red-fruited, wild species in the tomato clade, and the effects
of man-madedomestication.
Pathway engineering for efficient production of
astaxanthin in lettuce plants
Norihiko Misawa
Research Institute for Bioresources and Biotechnology, Ishikawa
Prefectural University, Suematsu, Nonoichi-machi, Ishikawa 921-
8836, Japan, n-misawa@ishikawa-pu.ac.jp
Among ketocarotenoids (carotenoids including 4-ketolated
β-ring), astaxanthin and canthaxanthin (specifically the former),
are commercially important pigments as nutraceuticals and cosmetics
that have anti-oxidation and anti-aging effects, while other
ketocarotenoids are likely to have industrial potentials. Pathway
engineering is to engineer biosynthetic pathways for compounds
of interests in heterologous organisms such as microbes and
higher plants. Pathway engineering researches for production of
astaxanthin have been performed in higher plants, by using
carotenoid β-ring 4(4’)-ketolase (4(4’)-oxygenase) genes, which
contain crtW, bkt1, bkt2, and crtO genes, as reviewed (Misawa,
2009). Recently, the marine bacterial (Brevundimonas sp.
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