Poster: Metabolic Engineering

Abs # 1021: Growing conditions greatly influence the accumulation of fruit carotenoid content in transgenic tomato plants overexpressing the lycopene b-cyclase gene.

Presenter:	D'Ambrosio, Caterina , cdambrosio@agrobios.it
Authors	D'Ambrosio, Caterina  (A)   Giorio, Giovanni  (A)   Stigliani, Adriana Lucia  (A)   Cellini, Francesco  (A)
Affiliations:	(A): Metapontum Agrobios

Tomato fruit is the most important accumulator of the carotenoid pigment lycopene. During early stages of fruit development, this pigment is readily cyclized to b-carotene by the plant enzyme lycopene b-cyclase (lcy-b). However, after breaker stage lycopene content starts to increase due to downregulation of lcy-b gene. The aim of this study was the increase of â-carotene content in tomato fruits through the modification of carotenogenesis via genetic engineering. Using a transgene conveying the tomato lcy-b cDNA we obtained plants (HighCaro) whose fruits showed very high content of b-carotene that in some cases reached the peak of 219.1 mg per g of fresh weight . Carotenogenesis in transgenic fruits was completely deregulated in such a way that cyclization of lycopene to b-carotene continued after breaker stage with the consequence that virtually all lycopene was converted to b-carotene. The effects of light and temperature on the ability to accumulate b-carotene were studied on T4 HighCaro genotypes. Results showed that these two factors could affect carotenogenesis in transgenic plants in contrast to control plants. These results demonstrate the feasibility of engineering tomato to divert carotenoid metabolic flux toward a desired useful end-product and that specific microclimatic conditions could increase performances of transgenic plants.