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Photosynthetic organisms use light harvesting antennae to expand the
wavelengths of light that are usable for photosynthesis. In
cyanobacteria, these light harvesting antennae are called phycobilisomes
(PBS). PBS capture light energy of specific wavelengths and funnel that
energy to photosystem II. Some cyanobacterial species can alter the
protein composition of the PBS to suite ambient light conditions. The
process of altering the pigment composition of the PBS in response to
light quality changes is called complementary chromatic adaptation (CCA)
and is thought to allow the organism to optimize photosynthesis. CCA
has been extensively studied in the cyanobacteria Fremyella diplosiphon and
the genes encoding several PBS proteins have been identified. Many of
these genes are transcribed in a light quality dependent manner. Light
quality also influences several other aspects of cellular morphology and
physiology. Therefore, many genes may be transcriptionally regulated by
light color. DNA microarray technology would allow us to compare the
transcriptomes of cells adapted to different light qualities. However,
most DNA microarrays rely on significant sequence information from an
entire genome: the genome of F. diplosiphon has not yet been sequenced.
We have adapted conventional microarray technology and developed genomic
DNA microarrays. Using this technology we have identified 19 novel
light-quality regulated genes in Fremyella diplosiphon.
Complete Introduction
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