THE EXPRESSION OF LIGHT-REGULATED GENES IN THE HIGH-PIGMENT-1 MUTANT OF TOMATO

Three light-regulated genes, chlorophyll a/b-binding protein (CAB), ri bulose-1,5-bisphosphate carboxylase/oxygenase small subunit, and chalc one synthase (CHS), are demonstrated to be upregulated in the high-pig ment-1 (hp-1) mutant of tomato (Lycopersicon esculentum Mill.) compare d with wild type (WT). However, the pattern of up-regulation of the th ree genes depends on the light conditions, stage of development, and t issue studied. Compared with WT, the hp-1 mutant showed higher CAB gen e expression in the dark after a single red-light pulse and in the per icarp of immature fruits. However, in vegetative tissues of light-grow n seedlings and adult plants, CAB mRNA accumulation did not differ bet ween WT and the hp-1 mutant. The ribulose-1,5-bisphosphate carboxylase /oxygenase small subunit mRNA accumulated to a higher level in the hp- 1 mutant than WT under all light conditions and tissues studied, where as CHS gene expression was up-regulated in deetiolated vegetative hp-1 -mutant tissues only. The CAB and CHS genes were shown to be phytochro me regulated and both phytochrome A and B1 play a role in CAB gene exp ression. These observations support the hypothesis that the HP-1 prote in plays a general repressive role in phytochrome signal transduction.