Abstract
We generated random mutations in
Synechococcus
sp. strain PCC 7942 to look for genes of output pathways in the cyanobacterial circadian system. A derivative of transposon Tn
5
was introduced into the chromosomes of reporter strains in which cyanobacterial promoters drive the
Vibrio harveyi luxAB
genes and produce an oscillation of bioluminescence as a function of circadian gene expression. Among low-amplitude mutants, one mutant, tnp6, had an insertion in a 780-bp open reading frame. The tnp6 mutation produced an altered circadian phasing phenotype in the expression rhythms of
psbAI
::
luxAB
,
psbAII
::
luxAB
, and
kaiA
::
luxAB
but had no or little effect on those of
psbAIII
::
luxAB
,
purF
::
luxAB
,
kaiB
::
luxAB
,
rpoD2
::
luxAB
,
ndhD
::
luxAB
, and
conII
::
luxAB
. This suggests that the interrupted gene in tnp6, named
cpmA
(circadian phase modifier), is part of a circadian output pathway that regulates the expression rhythms of
psbAI
,
psbAII
, and
kaiA
.
