Sigma70-like Transcription Factor Family
Allison. 2000: Expression of plastid genes is controlled at both transcriptional and
post-transcriptional levels in response to developmental and environmental signals. In
many cases this regulation is mediated by nuclear-encoded proteins acting in concert
with the endogenous plastid gene expression machinery. Transcription in plastids is
accomplished by two distinct RNA polymerase enzymes, one of which resembles eubacterial
RNA polymerases in both subunit structure and promoter recognition properties. The
holoenzyme contains a catalytic core composed of plastid-encoded subunits, assembled
with a nuclear-encoded promoter-specificity factor, sigma. Based on examples of
transcriptional regulation in bacteria, it is proposed that differential activation of
sigma factors may provide the nucleus with a mechanism to control expression of groups
of plastid genes. Hence, much effort has focused on identifying and characterizing
sigma-like factors in plants. While fractionation studies had identified several
candidate sigma factors in purified RNA polymerase preparations, it was only 4 years
ago that the first sigma factor genes were cloned from two photosynthetic eukaryotes,
both of which were red algae. More recently this achievement has extended to the
identification of families of sigma-like factor genes from several species of vascular
plants. Now, efforts in the field are directed at understanding the roles in plastid
transcription of each member of the rapidly expanding plant sigma factor gene family.
Recent results suggest that accumulation of individual sigma-like factors is controlled
by light, by plastid type and/or by a particular stage of chloroplast development.
These data mesh nicely with accumulating evidence that the core sigma-binding regions
of plastid promoters mediate regulated transcription in response to light-regime and
plastid type or developmental state. In this review I will outline progress made to
date in identifying and characterizing the sigma-like factors of plants, and in
dissecting their potential roles in chloroplast gene expression.
- Above description taken from
PlnTFDB.
Notes: Sigma70-like is missed in PlantTFDB and TOBFAC.
Sigma70-like TF searched via R2 domain,
R3 domain, and R4 domain.
6
Sigma70-like genes listed in PlnTFDB for Arabidopsis.
Last updated by Dr. Jeff Chen on May 23, 2009.