Changes in light sensitivity of photosynthesis in tobacco (Nicotiana tabacum) planes transformed with the antisense gene of glutamate-1-semialdehyde aminotransferase

Chlorophyll fluorescence and thermoluminescence were used to study photosyn thesis in tobacco transgenic plants, in which early stages of chlorophyll s ynthesis were inhibited owing to the expression of the glutamate-1-semialde hyde aminotransferase gene in the antisense orientation. When such plants w ere grown in weak light (30 mu Einstein/(m(2) s)), the chlorophyll a conten t was substantially reduced but the proportion of pigments in light-harvest ing complexes was little affected; photosystem II retained its activity, as established from fluorescence parameters. At the same time, changes in the optical properties of leaves in transgenic plants, caused by a reduction i n chlorophyll content, enhanced light sensitivity. When these transgenic pl ants were grown under standard illumination conditions (300 mu Einstein/(m( 2)s)), they experienced stress associated with partial photoinhibition of p hotosystem II activity, enhanced nonphotochemical dissipation of light. ene rgy, elevated rates of lipid peroxidation, and the consequent emission of h igh-temperature (120 degrees C) thermoluminescence of chlorophyll.