David L' Herrin Painter 2'24 2'18 lab 4713843 herrinmail'utexas'edu - PowerPoint PPT Presentation
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David L' Herrin Painter 2'24 2'18 lab 4713843 herrinmail'utexas'edu
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David L. Herrin. Painter 2.24 (2.18 lab) 471-3843. herrin_at_mail.utexas.edu ... psbA gene in Chlamydomonas has 4 group I introns that self-splice in vitro, ... – PowerPoint PPT presentation
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Title: David L' Herrin Painter 2'24 2'18 lab 4713843 herrinmail'utexas'edu
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David L. HerrinPainter 2.24 (2.18
lab)471-3843herrin_at_mail.utexas.edu
- A link to this presentation can be found at
http//www.esb.utexas.edu/herrin/bio344/
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Lab Projects
- I. Light-regulated splicing of the psbA introns
- psbA gene in Chlamydomonas has 4 group I introns
that self-splice in vitro, although poorly at 25?C
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Mobile
ORFs are not essential maturases. I2 and I4 ORFs
are homing endonucleases.
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psbA gene encodes the D1 polypeptide of PSII.
Strongly up-regulated by light.
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Lab Projects
- I. Light-regulated splicing of the psbA introns
- Splicing of psbA introns in vivo is slow in the
dark (in cells growing photoautotrophically),
increase at least 6-10-fold within 15 min of
light administration - Light stimulation does not require protein
synthesis but does require electron transport - Mechanism? Probably mediated by proteins.
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Genetic approach to get trans-acting factors
- Use suppressor genetics to identify genes that
promote splicing of psbA and rRNA introns - Identified at least 2 and probably 3 nuclear
genes (css1-css3) that can suppress deficiencies
in the rRNA and psbA4 introns - Currently trying to clone css1 using an arrayed
cosmid library
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The genetic model organism, Chlamydomonas
reinhardtii
All 3 genomes can be transformed.
- Nuclear genome
- 14 haploid chromosomes
- 100,000 KB
- Molecular map
- Draft genome sequence at 8X coverage
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Lab Projects
- II. Transcriptional regulation by the circadian
clock
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Circadian Rhythms
- Oscillate with a period of 24 hours
- Phase determined by light-dark cycle
- Once entrained, continue in constant conditions
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A Circadian System
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Relative transcription rates
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Plastid (Chloroplast) RNA polymerases in vascular
plants
Sigma subunit directs RNA polymerase to promoter
Fig. 6.31 in Buchanan et al.
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Lab Projects
- II. Transcriptional regulation by the circadian
clock - Chlamydomonas has 1 sigma factor-like gene
(sig1)!!
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Sig1 mRNA shows a circadian rhythm, peaking a few
h before the peak in chloroplast transcription.
LD ? LL
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II. Transcriptional regulation by the circadian
clock
- Role of the putative sigma factor for the
chloroplast (prokaryotic-like) RNA polymerase in
circadian control of chloroplast transcription - Approaches
- Biochemistry
- In vivo molecular and cellular analyses
- Microarrays
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