Genetic engineering of potato (Solanum tuberosum L.) for enhanced α-tocopherols and abiotic stress tolerance.

Vitamin E (α-tocopherol) is a lipid-soluble essential vitamin recognized for improvement in degenerative health conditions, abating cancer risk, and coronary heart diseases in humans. While in plants, it acts as a free radical scavenger that protects cells against oxidative and photooxidative damages. The daily consumption of potato makes it a key target for biofortification with vitamins for eliminating vitamin deficiency in large populations. Vitamin E biosynthetic pathway genes have been overexpressed in plants via genetic engineering to enhance the α-tocopherol content. Major genes involved in the vitamin E biosynthesis in plants viz. the homogentisate-phytyltransferase (At-HPT) and γ-tocopherol-methyltransferase (At-γ-TMT), isolated from Arabidopsis were constitutively overexpressed in potato (Solanum tuberosum L.). The molecular analyses of independent transgenic lines revealed a stable integration of both the genes in the plant genome. The transgenic potato exhibited significantly improved vitamin E contents up to 173-258% in comparison to the untransformed control plants. Transgenic tissues also exhibited increased cellular antioxidant enzymes, proline, osmolyte, and glutathione content that are directly correlated with the ability of the plant to withstand abiotic stresses imposed by salt (NaCl) and heavy metal (CdCl2 ). Therefore, the current strategy of increasing the vitamin E content in potato with enhanced tolerance to abiotic stresses might greatly aid efforts to engineer crops for human health benefits and greater yield under adverse environmental conditions.

Overexpression of PDX-II gene in potato (Solanum tuberosum L.) leads to the enhanced accumulation of vitamin B6 in tuber tissues and tolerance to abiotic stresses.

Vitamin B6 is a vital metabolite required for living organisms as a cofactor in several metabolic biochemical reactions and recognized as a potent antioxidant molecule which modulates the expression of the proteins responsible for the scavenging of cellular reactive oxygen species. It is well established that the microorganisms and plants can synthesize the B6 de novo, therefore, all the animals including humans must acquire it from the plant dietary resources. However, the bioavailability of the vitamin in the edible portions of the commonly consumed plants is insufficient to meet the daily recommended doses. Genetic engineering techniques have proven successful in increasing the vitamin B6 content in the model plants. Present study describe the development of transgenic potato (Solanum tuberosum L. cv. Kufri chipsona) overexpressing key vitamin B6 pathway gene, the PDXII (NCBI database Ref. ID- NM_125447.2) isolated from Arabidopsis thaliana under the control of CaMV 35S constitutive promoter. The stable integration and expression of transgene in the transgenic lines were confirmed by PCR, Southern blot and RT-PCR analysis. Transgenic tubers exhibited considerably improved vitamin B6 accumulation (up to 107-150%) in comparison to the untransformed controls potato. This increase in vitamin B6 was also correlated with the increased mRNA expression of PDXII gene. The prominent increase in the B6 content of transgenic potato was also associated with the capability to survive under abiotic stresses, therefore, the transgenic lines were able to withstand various abiotic stresses imposed by salinity (NaCl) or methyl viologen (MV). We thus demonstrated that overexpression of PDXII gene under the control of a constitutive promoter enhanced the accumulation of the vitamin B6 which also augmented the tolerance under various abiotic stresses in potato (Solanum tuberosum L.).

Biotechnological improvement of nutritional and therapeutic value of cultivated potato.

Genetic engineering is recognized as a powerful tool for altering the genetic characteristic of crop plants. Genetic engineering has tremendous potential in developing improved potato varieties with desired agronomic traits and has been utilized for improvement of several crop plants including potato to enhance essential amino acid, protein and lipids/carbohydrates contents as well to improve stress tolerance. The pathway engineering of amino acid revealed dramatic changes in essential amino acid content and protein quality. Similarly, the vitamin pathway engineering of potato has been proved to enhance the vitamin content with increased cellular antioxidant activities. Secondary metabolites such as flavonoids have also been altered through the genetic engineering of potato. This review provides detailed reports on the advances made in genetic transformation of potato for enrichment in its nutritional and therapeutic value by an increase in functional secondary metabolites, carbohydrate, essential amino acids, proteins, lipids, vitamins and edible vaccines.