The influence of transgenes on the synthesis of provitamin A type carotenoids in selected crops.

Vitamin A je skupina v maščobi topnih spojin, ki jih človek sam ni zmožen sintetizirati, zato morajo biti široko prisotne v človeški prehrani. Če pride do pomanjkanja vitamina, lahko to vodi v številne težave, med drugim tudi do slepote, kar poleg lakote predstavlja precej velik problem v večini držav v razvoju, kjer škrobna prehrana prebivalstva ne vsebuje zadostnih količin omenjenega vitamina. V ta namen so znanstveniki razvili številne kulturne rastline, ki imajo povečano sintezo in kopičenje provitamina A, ki se v človeškem organizmu pretvori v funkcionalen vitamin A. To so dosegli z metodami biofortifikacije (s konvencionalnim križanjem in z genetskim inženiringom kulturnih rastlin) in s pomočjo 2 pristopov: prekomerne ekspresije in utišanja genov. Uporabljene metode so privedle do znatnega kopičenja karotenoidov v užitnih delih riža, paradižnika, krompirja in koruze ter do očitne spremembe barve plodov le-teh, ki so z večjo vsebnostjo karotenoidov kazale bolj intenzivne odtenke oranžne oz. rumene barve. Za uspešno manipulacijo karotenogeneze pa je ključnega pomena temeljito razumevanje biosintezne poti karotenoidov, katere poznavanje je igralo ključno vlogo pri izbiri posameznih genov. Pri opisanih kulturnih rastlinah so bili geni predvsem bakterijskega izvora (rod Erwinia), uporabljeni pa so bili tudi rastlinski geni, tako endogeni kot tudi geni iz drugih rastlinskih vrst, ki že same po sebi vsebujejo večje količine karotenoidov.Vitamin A is a group of fat-soluble compounds that humans cannot synthesize themselves, so they must be widely present in the human diet. If there is a deficiency of the vitamin, it can lead to many problems, including blindness, which, in addition to hunger, is a big problem in most developing countries where the starchy diet of the population does not contain sufficient amounts of said vitamin. For this purpose, scientists have developed several cultivated crops that have increased synthesis and accumulation of provitamin A, which is converted into functional vitamin A in the human body. This was achieved by biofortification methods (conventional crossing and genetic engineering of cultivated crops) and by means of 2 approaches: overexpression and gene silencing. The methods used led to a significant accumulation of carotenoids in the edible parts of rice, tomatoes, potatoes and corn, and to an obvious change in the colour of their fruits, which, with a higher content of carotenoids, showed more intense shades of orange or yellow colour. For the successful manipulation of carotenogenesis, a thorough understanding of the biosynthesis pathway of carotenoids is crucial and played a key role in the selection of individual genes. In the cultivated plants described, the genes were mainly of bacterial origin (genus Erwinia), but plant genes were also used, both endogenous and genes from other plant species, which by themselves contain larger amounts of carotenoids