CHARACTERIZATION OF A LIGHT-RESPONDING TRANSACTIVATOR RESPONSIBLE FORDIFFERENTIALLY CONTROLLING REACTION-CENTER AND LIGHT-HARVESTING-I GENE-EXPRESSION IN RHODOBACTER-CAPSULATUS
Jj. Buggy et al., CHARACTERIZATION OF A LIGHT-RESPONDING TRANSACTIVATOR RESPONSIBLE FORDIFFERENTIALLY CONTROLLING REACTION-CENTER AND LIGHT-HARVESTING-I GENE-EXPRESSION IN RHODOBACTER-CAPSULATUS, Journal of bacteriology, 176(22), 1994, pp. 6936-6943
The purple nonsulfur photosynthetic bacterium Rhodobacter capsulatus r
egulates synthesis of its photosystem in response to two environmental
stimuli, oxygen tension and light intensity. Here we describe the ide
ntification and characterization of the trans-acting regulatory gene h
vrA, which we show is involved in differentially controlling reaction
center and light-harvesting gene expression in response to alterations
in light intensity. An hvrA mutant strain is shown to lack the capabi
lity to trans-activate light-harvesting-I and reaction center gene exp
ression but retain normal light-harvesting-II and photopigment regulat
ion, in response to a reduction in light intensity. As a consequence o
f altered expression, hvrA mutant strains exhibit reduced photosynthet
ic growth capabilities under dim-light conditions. The results of this
study acid additional studies indicate that regulated synthesis of th
e photosystem involves complex sets of overlapping regulatory circuits
that differentially control photosystem gene expression in response t
o environmental stimuli such as oxygen tension and light intensity.