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Role of photosynthesis and analysis of key enzymes involved in primary metabolism throughout the lifespan of the tobacco flower.

Although the physiological and economical relevance of flowers is recognized, their primary metabolism during development has not been characterized, especially combining protein, transcript, and activity levels of the different enzymes involved. In this work, the functional characterization of the photosynthetic apparatus, pigment profiles, and the main primary metabolic pathways were analysed in tobacco sepals and petals at different developmental stages. The results indicate that the corolla photosynthetic apparatus is functional and capable of fixing CO(2); with its photosynthetic activity mainly involved in pigment biosynthesis. The particular pattern of expression, across the tobacco flower lifespan, of several proteins involved in respiration and primary metabolism, indicate that petal carbon metabolism is highest at the anthesis stage; while some enzymes are activated at the later stages, along with senescence. The first signs of corolla senescence in attached flowers are observed after anthesis; however, molecular data suggest that senescence is already onset at this stage. Feeding experiments to detached flowers at anthesis indicate that sugars, but not photosynthetic activity of the corolla, are capable of delaying the senescence process. On the other hand, photosynthetic activity and CO(2) fixation is active in sepals, where high expression levels of particular enzymes were detected. Sepals remained green and did not show signs of senescence in all the flower developmental stages analysed. Overall, the data presented contribute to an understanding of the metabolic processes operating during tobacco flower development, and identify key enzymes involved in the different stages.