INVESTIGADORES
MAZZELLA Maria Agustina
artículos
Título:
Dual effect of phytochrome A on hypocotyi growth under continuous red light
Autor/es:
MAZZELLA MA, ALCONADA MAGLIANO MT, CASAL JJ
Revista:
Plant Cell and environment
Editorial:
Wiley online library
Referencias:
Año: 1997 vol. 20 p. 261 - 267
ISSN:
1365-3040
Resumen:
Tbe role of pbytocbrome A in tbe control of bypocotyl
growtb under continuous red ligbt (Re) was investigated
using phyA and phyB mutants of Arabidopsis thaliana,
wbicb lack pbytochrome A (pbyA) or pbytocbrome B
(pbyB), respeetively, and transgenie seedlings of Nicotiana
tabacum overexpressing Avena pbyA, compared to tbe
corresponding wild type (WT). In WT seedlings of A.
thaliana, hypocotyl growtb inhibition showed a biphasic
response to the fluence rate of Re, with a brake at
10 /imol m s . At equal total fluence rate, hourly
pulses of red light caused slightly more inhibition than Re.
The response to very low fluences of eontinuous or pulsed
red light was absent in the phyA and phyA phyB mutants
and present in the phyB mutant. The second part of the
response was steeper in the phyA mutant than in the WT
but was absent in the phyB mutant. In WT tobacco the
response to Re was biphasic. Overexpression of Avena
phyA enhanced the response only at very low fluence rates
of Re (< 10"^ ;UmoI m~^ s"'). In both species, the effect of
hourly pulses of far-red light was similar to the maximum
inhibition observed in the first phase of the response to Re.
Using reciprocity failure (i.e. higher inhibition under continuous
than pulsed light) as the operational criterion, a
'true' high-irradianee reaction occurred under continuous
far-red light but not under Re or red plus far-red light
mixtures. Native and overexpressed phyA are proposed to
mediate very low fluence responses under Re. In WT A.
thaliana, this effeet is eounteraeted by a negative action of
phyA on phyB-mediated low-fluenee responses.