ISHS Acta Horticulturae 789: XV Meeting of the EUCARPIA Tomato Working Group
OVER-EXPRESSION OF CAROTENE β-HYDROXYLASE 1 (CRTR-B1) AND LYCOPENE β-CYCLASE (LCY-B) IN TRANSGENIC TOMATO FRUITS |
| Authors: | G. Giorio, A.L. Stigliani, C. D'Ambrosio |
| Keywords: | carotenoids, xanthophylls, carotenoid beta-hydroxylase, lycopene beta-cyclase |
| Abstract:
The present study explored the possibility of converting the high amount of beta-carotene of HighCaro fruits into derived xanthophylls by the over-expression of CrtR-b1 cDNA encoding the putative  -carotene hydroxylase 1 of tomato.
Double transgenic plants were obtained crossing the HighCaro (HC) line conveying the Lcy-b transgene insertion, hc1, to HY line carrying two distinct CrtR-b1 transgene insertions, hy1 and hy2. Results of Southern and quantitative Real-Time PCR analyses on hybrid plants indicated that hy2 insertion of CrtR-b1 transgene exerted a co-suppression effect on CrtR-b1 expression and interestingly an in trans silencing effect on Lcy-b, resulting in a reduction of transcript levels of both transgenes.
For this reason, plants carrying hc1 and hy2 insertions produced red instead of orange fruits while plants carrying the hc1 and hy1 insertions produced orange coloured fruits.
HPLC analysis results confirmed that the former fruits contained very low levels of beta-carotene.
However, concurrent over-expression of lycopene -cyclase (Lcy-b) and -carotene hydroxylase 1 (CrtR-b1) in plants carrying the hy1 and hc1 transgenes did not result in any appreciable increase of the total carotenoids nor of xanthophyll or zeaxanthin fruit contents compared to the over-expression of the sole hc1 transgene.
A couple of hypotheses were formulated to explain these results.
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