Resumo

LOPEZ EMPARAN, A.; GAJARDO, H.; STANGE, C. R.  e  FEDERICO, M. L. Metabolic engineering of carotenoid content in Brassica napus L. through seed-specific overexpression of an endogenous PSY gene. Rev. agron. noroeste arg. [online]. 2017, vol.37, n.2, pp.133-143. ISSN 0080-2069.

In plants, the first committed step of the carotenoid biosynthetic pathway is catalyzed by the enzyme phytoene synthase (PSY). PSY catalyzes the condensation of two molecules of geranyl-geranyl diphosphate to produce phytoene, a colorless carotenoid. Overexpression of bacterial (CrtB) and plant PSY genes have increased seed carotenoid content in several plant species. In many instances, the choice of transgene has proven crucial in achieving higher carotenoid levels in transgenic plants. In rapeseed, overexpression of CrtB increased seed carotenoid levels 50 fold but the overexpression of a plant or endogenous PSY has not been reported to date. In this study, the aim was to further increase seed carotenoid content by over-expressing one of the six endogenous PSY genes present in this crop. Using an Agrobacterium-mediated transformation, we introduced a binary vector containing BnaC.PSYa coding region under the control of the soybean lectin promoter (pCambia2300-Lec:: BnaC.PSYa-6XHys) into Brassica napus cv. Westar. Six fertile transgenic events were recovered and confirmed by PCR analysis. Transgene expression was followed by conventional and quantitative real time RT-PCR in T3 seeds at 30 and 60 days post anthesis (dpa). All events over-expressed BnaC.PSYa-6XHys and no silencing of the PSY gene family members was detected. However, seed carotenoid profiling and quantification by HPLC revealed that only a minimal increase (2X) in carotenoid content was obtained. Future strategies to maximize seed carotenoid content in rapeseed are discussed.

Palavras-chave : Biofortification; Rapeseed; Phytoene synthase; Lutein.