S. Frances et Wf. Thompson, THE DARK-ADAPTATION RESPONSE OF THE DEETIOLATED PEA MUTANT LIP1 IS MODULATED BY EXTERNAL SIGNALS AND ENDOGENOUS PROGRAMS, Plant physiology, 115(1), 1997, pp. 23-28
The lip1 mutant of pea (Pisom sativum L.) exhibits a de-etiolated phen
otype. When grown in darkness, lip1 plants have several characteristic
s normally associated only with light-grown plants. Young wild-type (W
T) seedlings accumulate high levels of transcripts from plastid-relate
d genes (such as those encoding chlorophyll a/b-binding proteins, ferr
edoxin, and the small subunit of Rubisco) only in the light. In contra
st, regardless of the light conditions under which the plants are grow
n, young mutant seedlings accumulate transcript levels equal to or gre
ater than those seen in light-grown WT seedlings of the same age. Unde
r some conditions, light-grown lip1 seedlings failed to respond to dar
k treatment. The largest response to darkness observed in the mutant o
ccurred when older seedlings were first grown under low-light conditio
ns before transfer to darkness. The mutant's inability to respond to d
arkness is not due to a gross disturbance in the circadian clock. We c
onclude that environmental signals (light) and endogenous programs (de
velopmental and circadian) regulate gene expression in both WT and mut
ant plants. However, mutant seedlings exhibit a developmentally regula
ted and exaggerated response to light. In addition, the effect of the
mutation may be greatest during a brief period early in development.