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Sigma factor-mediated plastid retrograde signals control nuclear gene expression
Jesse D Woodson1, Juan M Perez-Ruiz1,2, Robert J Schmitz1,2,3
1Plant Biology Laboratory, The Salk Institute, 10010 North Torrey Pines Road, La Jolla, CA, 92037, USA.
The Plant Journal : for Cell and Molecular Biology
|September 7, 2012
Summary
Retrograde signals from plastids regulate nuclear gene expression. Sigma factors (SIG) control these signals, with SIG2 and SIG6 showing redundant roles in plastid transcription and signaling.
Area of Science:
- Plant molecular biology
- Organelle communication
- Gene regulation
Background:
- Retrograde signaling from plastids to the nucleus is crucial for regulating the organelle's proteome.
- Hundreds of nuclear genes are controlled by plastid-derived retrograde signals, especially during photoautotrophy establishment and environmental changes.
- Plastid gene expression is a known source of retrograde signals, but the number and mechanisms of these signals remain unclear.
Purpose of the Study:
- To investigate the role of plastid gene expression in retrograde signaling.
- To identify specific sigma factors (SIG) involved in plastid transcription and their impact on nuclear gene expression.
- To elucidate the mechanisms and number of retrograde signals originating from plastids.
Main Methods:
- Analysis of Arabidopsis mutants defective in the six sigma factor (SIG) genes.
- Investigating the effects of GUN1 (a pentatricopeptide repeat protein) and heme synthesis on nuclear gene expression in sig2 and sig6 mutants.
- Microarray analysis to identify nuclear genes regulated by SIG-dependent retrograde signals.
Main Results:
- SIG2 and SIG6 exhibit partially redundant functions in plastid transcription and retrograde signaling.
- Loss of GUN1 restored nuclear gene expression in sig2 and sig6 mutants, while increased heme synthesis only rescued sig2 mutants.
- Two distinct retrograde signals originating from sigma factor function were identified, one potentially involving tRNA(Glu) transcription.
Conclusions:
- Sigma factor function is the source of at least two distinct retrograde signals to the nucleus.
- These signals regulate a subset of nuclear genes affected by plastid biogenesis inhibitors like norflurazon and lincomycin.
- Plastid transcription is implicated as a key process affected by these inhibitors, inducing retrograde signaling.
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