A 146 bp fragment of the tobacco Lhcb1*2 promoter confers very-low-fluence, low-fluence and high-irradiance responses of phytochrome to a minimal CaMV 35S promoter.
The occurrence of very-low-fluence responses (VLFR), low-fluence responses (LFR) and high-irradiance responses (HIR) of phytochrome was investigated for the expression of the gene of beta-glucuronidase (gusA) under the control of the tobacco Lhcb1*2 promoter, in etiolated transgenic tobacco seedlings. The activity of beta-glucuronidase (GUS) showed biphasic responses to the calculated proportion of Pfr provided by light pulses. The first phase (i.e. the VLFR) showed a maximum for Pfr levels characteristic of far-red light. The second phase (i.e. the LFR) was observed at higher Pfr levels and was reversible by far-red light pulses. The strong effect of continuous far-red light (i.e. HIR) was fluence-rate-dependent and could not be replaced either by hourly pulses of the same spectral composition and total fluence or by very low fluences of red light. Deletion of the Lhcb1*2 promoter to -453 caused little loss of GUS activity. The -453 to -31, -270 to -31 and -176 to -31 fragments of the Lhcb1*2 promoter conferred proportionally normal VLFR, LFR and HIR to a truncated (-46 to +8) CaMV 35S minimal promoter. This is the first demonstration of the presence of three phytochrome action modes in the control of the transcriptional activity of a single gene. The cis-acting regulatory elements necessary for VLFR, LFR and HIR are present in a 146 bp fragment of the tobacco Lhcb1*2 promoter.
Cerdán
P D
PD
Instituto de Investigaciones Bioquímicas Fundación Campomar, Buenos Aires, Argentina.
Staneloni
R J
RJ
Casal
J J
JJ
Sánchez
R A
RA
D001483:Base Sequence; D017796:Caulimovirus / Q000235:genetics*; D015870:Gene Expression / Q000528:radiation effects; D005966:Glucuronidase / Q000096:biosynthesis; D007700:Kinetics; D008027:Light; D008969:Molecular Sequence Data; D010834:Phytochrome / Q000502:physiology* / Q000528:radiation effects; D010947:Plants, Toxic; D011401:Promoter Regions, Genetic / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D014026:Nicotiana / Q000235:genetics / Q000502:physiology*
D011993:Recombinant Fusion Proteins; D010834:Phytochrome; D005966:Glucuronidase