Affiliation:
1. Thallia Pharmaceuticals S.A. L'Orée d'Ecully, 69132 Ecully cedex, France,1 and
2. Department of Plant Biology and Center for the Study of Early Events in Photosynthesis, Arizona State University, Tempe, Arizona 85287-16012
Abstract
ABSTRACT
The
psbAII
locus was used as an integration platform to overexpress genes involved in carotenoid biosynthesis in
Synechocystis
sp. strain PCC 6803 under the control of the strong
psbAII
promoter. The sequences of the genes encoding the yeast isopentenyl diphosphate isomerase (
ipi
) and the
Synechocystis
β-carotene hydroxylase (
crtR
) and the linked
Synechocystis
genes coding for phytoene desaturase and phytoene synthase (
crtP
and
crtB
, respectively) were introduced into
Synechocystis
, replacing the
psbAII
coding sequence. Expression of
ipi
,
crtR
, and
crtP
and
crtB
led to a large increase in the corresponding transcript levels in the mutant strains, showing that the
psbAII
promoter can be used to drive transcription and to overexpress various genes in
Synechocystis
. Overexpression of
crtP
and
crtB
led to a 50% increase in the myxoxanthophyll and zeaxanthin contents in the mutant strain, whereas the β-carotene and echinenone contents remained unchanged. Overexpression of
crtR
induced a 2.5-fold increase in zeaxanthin accumulation in the corresponding overexpressing mutant compared to that in the wild-type strain. In this mutant strain, zeaxanthin becomes the major pigment (more than half the total amount of carotenoid) and the β-carotene and echinenone amounts are reduced by a factor of 2. However, overexpression of
ipi
did not result in a change in the carotenoid content of the mutant. To further alter the carotenoid content of
Synechocystis
, the
crtO
gene, encoding β-carotene ketolase, which converts β-carotene to echinenone, was disrupted in the wild type and in the overexpressing strains so that they no longer produced echinenone. In this way, by a combination of overexpression and deletion of particular genes, the carotenoid content of cyanobacteria can be altered significantly.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
206 articles.
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