Abstract
BackgroundSince the creation of “Golden Rice”, biofortification of plant-derived foods is a promising strategy for the alleviation of nutritional deficiencies. Potato is the most important staple food for mankind after the cereals rice, wheat and maize, and is extremely poor in provitamin A carotenoids.MethodologyWe transformed potato with a mini-pathway of bacterial origin, driving the synthesis of beta-carotene (Provitamin A) from geranylgeranyl diphosphate. Three genes, encoding phytoene synthase (CrtB), phytoene desaturase (CrtI) and lycopene beta-cyclase (CrtY) from Erwinia, under tuber-specific or constitutive promoter control, were used. 86 independent transgenic lines, containing six different promoter/gene combinations, were produced and analyzed. Extensive regulatory effects on the expression of endogenous genes for carotenoid biosynthesis are observed in transgenic lines. Constitutive expression of the CrtY and/or CrtI genes interferes with the establishment of transgenosis and with the accumulation of leaf carotenoids. Expression of all three genes, under tuber-specific promoter control, results in tubers with a deep yellow (“golden”) phenotype without any adverse leaf phenotypes. In these tubers, carotenoids increase approx. 20-fold, to 114 mcg/g dry weight and beta-carotene 3600-fold, to 47 mcg/g dry weight.ConclusionsThis is the highest carotenoid and beta-carotene content reported for biofortified potato as well as for any of the four major staple foods (the next best event being “Golden Rice 2”, with 31 mcg/g dry weight beta-carotene). Assuming a beta-carotene to retinol conversion of 6∶1, this is sufficient to provide 50% of the Recommended Daily Allowance of Vitamin A with 250 gms (fresh weight) of “golden” potatoes.
Highlights
Potato (Solanum tuberosum) originated in the highlands of South America, where it has been cultivated for over 2.000 years
In this paper we report the results of a systematic investigation, aimed at verifying which is the optimal combination of promoters and transgenes, able to maximally increase the provitamin A content of potato tubers without affecting vegetative characteristics
The ORFs were fused to the RbcS transit peptide to direct the encoded protein into plastids (Figure 1B)
Summary
Since the creation of ‘‘Golden Rice’’, biofortification of plant-derived foods is a promising strategy for the alleviation of nutritional deficiencies. Potato is the most important staple food for mankind after the cereals rice, wheat and maize, and is extremely poor in provitamin A carotenoids. Three genes, encoding phytoene synthase (CrtB), phytoene desaturase (CrtI) and lycopene beta-cyclase (CrtY) from Erwinia, under tuberspecific or constitutive promoter control, were used. Expression of all three genes, under tuberspecific promoter control, results in tubers with a deep yellow (‘‘golden’’) phenotype without any adverse leaf phenotypes. This is the highest carotenoid and beta-carotene content reported for biofortified potato as well as for any of the four major staple foods (the best event being ‘‘Golden Rice 2’’, with 31 mcg/g dry weight beta-carotene).
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