The dark-adaptation response of the de-etiolated pea mutant lip1 is modulated by external signals and endogenous programs.

摘要

The lip1 mutant of peas (Pisum sativum) exhibits a de-etiolated phenotype. When grown in darkness, lip1 plants showed several characteristics normally associated only with light-grown plants. Young wild-type (WT) seedlings accumulated high levels oftranscripts from plastid-related genes (such as those encoding chlorophyll a/b-binding proteins, ferredoxin, and the small subunit of Rubisco) only in the light. In contrast, regardless of the light conditions under which the plants were grown, young mutant seedlings accumulated transcript levels equal to or greater than those seen in light-grown WT seedlings of the same age. Under some conditions, light-grown lip1 seedlings failed to respond to dark treatment. The largest response to darkness observedin the mutant occurred when older seedlings were first grown under low-light conditions before transfer to darkness. The mutant's inability to respond to darkness was not due to a gross disturbance in the circadian clock. It was concluded that environmental signals (light) and endogenous programs (developmental and circadian) regulate gene expression in both WT and mutant plants. However, mutant seedlings exhibit a developmentally regulated and exaggerated response to light. In addition, the effect ofthe mutation may be greatest during a brief period early in development.