ACTA BIOLOGICA CRACOVIENSIA

16 TH INTERNATIONAL SYMPOSIUM ON CAROTENOIDS
SD212) crtW and crtZ (carotenoid β-ring 3(3’)-hydroxylase) genes,
whose nucleotide sequence is modified to codon usage of higher
plants, were successfully overexpressed in the chloroplasts of
tobacco plants (Nicotiana tabacum), and astaxanthin level produced
there reached 5.44 mg·g -1 dry weight (74% of total
carotenoids) (Hasunuma et al., 2008). This finding means that
direct expression of the foreign genes in plant chloroplasts is a
promising approach for efficient production of astaxanthin. We
performed chloroplast transformation of an edible plant lettuce
(Lactuca sativa), and expressed three key genes for ketocarotenoid
biosynthesis in lettuce leaves, which were the crtW
and crtZ genes, and the idi gene originated from marine bacterium
Paracoccus sp. N81106. Subsequent transplastomic lettuce
plants produced astaxanthin predominantly, along with other
ketocarotenoids such as fritshiellaxanthin (4-ketolutein), 4ketoantheraxanthin
and canthaxanthin, and another commercially
important carotenoid lutein.
REFERENCES
MISAWA N. 2009. Pathway engineering of plants toward astaxanthin
production. Plant Biotechnol 26: 93-99.
HASUNUMA T, MIYAZAWA S, YOSHIMURA S, SHINZAKI Y, TOMIZAWA K, SHINDO
K, CHOI SK, MISAWA N, MIYAKE C. 2008. Biosynthesis of astaxanthin
in tobacco leaves by transplastomic engineering. Plant J 55:
857-868.
Transcriptional regulation of phytoene
synthase levels in Arabidopsis
Manuel Rodríguez-Concepción
Centre for Research in Agricultural Genomics (CRAG)
CSIC-IRTA-UAB. Campus UAB Bellaterra, 08193 Barcelona, Spain,
manuel.rodriguez@cragenomica.es
Carotenoids are isoprenoid pigments synthesized by all photosynthetic
organisms and some non-photosynthetic bacteria and
fungi. In plants, they play central roles in photosynthesis and
photoprotection and provide color to non-photosynthetic roots,
flowers and fruits. Additionally, their oxidative cleavage generates
apocarotenoids such as the hormones abscisic acid (ABA) and
strigolactones that regulate plant development and responses to
external stimuli. However, the molecular mechanisms controlling
plant carotenogenesis are not well understood yet.
The metabolic precursors for plant carotenoid biosynthesis
derive from the methylerythritol 4-phosphate (MEP) pathway and
are shared by other plastidial pathways leading to the production
of different isoprenoid-end products such as gibberellins and the
side chain of tocopherols and chlorophylls. Such MEP-derived
precursors are specifically channelled to the carotenoid pathway
by the enzyme phytoene synthase (PSY). Environmental factors
such as light and salt stress are important regulators of PSY
accumulation at the gene expression level. We have shown that
the only gene encoding PSY in Arabidopsis thaliana is repressed
in dark-grown seedlings by direct binding of the phytochromeinteracting
transcription factor PIF1 to specific motifs in the PSY
promoter. Degradation of PIF1 upon interaction with photoactivated
phytochromes during deetiolation results in a rapid derepression
of PSY gene expression and a burst in the production of
carotenoids in coordination with chlorophyll biosynthesis and
chloroplast development for an optimal transition to photosynthetic
metabolism. Our data on the regulation of PSY expression
by PIFs beyond deetiolation and by other transcripcion factors in
response to salt stress will also be presented.
Carotenogenesis in the potato tuber
Mark A. Taylor
Plant Products and Food Quality, James Hutton Institute,
Invergowrie, Dundee, DD2 5DA, UK, mark.taylor@hutton.ac.uk
Despite extensive studies characterising the biosynthetic genes
involved in the carotenoid pathway little is known about the
mechanisms regulating carotenoid accumulation in non-green tissues.
Early transgenic studies have demonstrated that tubers
have the capacity to accumulate nutritionally significant levels of
a range of carotenoids, either by manipulation of biosynthesis
using single or combinations of transgenes, or by altering the sink
capacity for storage of carotenoids. We have used a range of techniques
in an attempt to discover the genes that underpin natural
variation in potato tuber carotenoid content. Two diploid populations
that segregate for tuber carotenoid content were developed
and dense genetic maps were constructed. Two major QTL,
affecting overall tuber carotenoid content were identified on chromosome
3 and 9. Whereas a known biosynthetic gene was shown
to underpin the QTL on chromosome 3 (crtR-b2), no known
biosynthetic gene maps to the chromosome 9 QTL. A genetical
genomics approach was used to identify candidate genes for this
QTL. Further QTL associated with different aspects of tuber
carotenoid content, are being studied.
Additional candidate genes for tuber carotenoid content have
been identified in a series of microarray experiments, analysing
samples bulked according to individual carotenoid traits.
Transgenic potato plants have been developed silencing one of
these candidate genes encoding a carotenoid cleavage dioxygenase
(CCD4), resulting in increased levels of tuber carotenoids and
unexpected effects on tuber morphology that mimic a heat
sprouting phenotype (Campbell et al., 2010). Another carotenoid
cleavage dioxygenases (CCD8) was also silenced resulting in
major effects on stolon and tuber development.
A key issue in understanding tuber carotenoid accumulation
is the nature of the organelle in which carotenoids accumulate. To
address this, transgenic lines in which carotenoid synthesis related
enzymes have been tagged with RFP have been developed. The
localisation of the carotenoid biosynthetic enzymes was revealed
by this analysis, with different locations for phytoene synthase
and β-carotene hydroxylase.
This work was funded by EU-FP7 METAPRO 244348.
SESSION 6
REFERENCE
CAMPBELL R, DUCREUX LJM, MORRIS WL, MORRIS JA, SUTTLE JC, RAMSAY
G, BRYAN GJ, HEDLEY PE, TAYLOR MA. 2010. The metabolic and
developmental roles of carotenoid cleavage dioxygenase 4 from
potato (Solanum tuberosum L). Plant Physiology 154: 656-664.
The revised carotenoid biosynthetic pathway
in plants and discoveries for obtaining
sustainable agricultural solutions to global
vitamin A deficiency
Eleanore T. Wurtzel
Department of Biological Sciences, Lehman College and Graduate
School, City University of New York, USA 250 Bedford Park
Boulevard West, Bronx, NY 10468 USA,
wurtzel@lehman.cuny.edu,
http://maize.lehman.cuny.edu/webwurtzel/wurtzelhomepage/wurtzel.html
Development of cereal crops with increased provitamin
A carotenoids could provide a sustainable solution to eliminating
the global health problem of vitamin A deficiency. Maize is a
major staple carbohydrate source and an important model for
84 ACTA BIOLOGICA CRACOVIENSIA Series Botanica