Increase of sulphur-containing amino acids in transgenic potato with 10 ku zein gene from maize

Genetic Engineering: A Possible Strategy for Protein-Energy Malnutrition Regulation

Protein-energy malnutrition (PEM) has adversely affected the generations of developing countries. It is a syndrome that in severity causes death. PEM generally affects infants of 1-5 age group. This manifestation is maintained till adulthood in the form of poor brain and body development. The developing nations are continuously making an effort to curb PEM. However, it is still a prime concern as it was in its early years of occurrence. Transgenic crops with high protein and enhanced nutrient content have been successfully developed. Present article reviews the studies documenting genetic engineering-mediated improvement in the pulses, cereals, legumes, fruits and other crop plants in terms of nutritional value, stress tolerance, longevity and productivity. Such genetically engineered crops can be used as a possible remedial tool to eradicate PEM.

Overexpression of GsGSTU13 and SCMRP in Medicago sativa confers increased salt-alkaline tolerance and methionine content

Tau-class glutathione S-transferases (GSTUs) are ubiquitous proteins encoded by a large gene family in plants, which play important roles in combating different environmental stresses. In previous studies, we constructed a Glycine soja transcriptional profile, and identified three GSTUs (GsGSTU13, GsGSTU14 and GsGSTU19) as potential salt-alkaline stress-responsive genes. Two of them, GsGSTU14 and GsGSTU19, have been shown to positively regulate plant salt-alkaline tolerance. In this study, we further demonstrated the positive function of GsGSTU13 in plant salt-alkaline stress responses by overexpressing it in Medicago sativa. Stress tolerance tests suggested that GsGSTU13 transgenic lines showed better growth and physiological indicators than wild alfalfa (cv. Zhaodong) under alkaline stress. Considering the shortage of methionine in alfalfa, we then co-transformed GsGSTU13 into two main alfalfa cultivars in Heilongjiang Province (cv. Zhaodong and cv. Nongjing No. 1) together with SCMRP, a synthesized gene that could improve the methionine content. We found that GsGSTU13/SCMRP transgenic alfalfa displayed not only higher methionine content but also higher tolerance to alkaline and salt stresses, respectively. Taken together, our results demonstrate that GsGSTU13 acts as a positive regulator in plant responses to salt and alkaline stresses, and can be used as a good candidate for generation of salt-alkaline tolerant crops.

Ectopic expression of GsPPCK3 and SCMRP in Medicago sativa enhances plant alkaline stress tolerance and methionine content

So far, it has been suggested that phosphoenolpyruvate carboxylases (PEPCs) and PEPC kinases (PPCKs) fulfill several important non-photosynthetic functions. However, the biological functions of soybean PPCKs, especially in alkali stress response, are not yet well known. In previous studies, we constructed a Glycine soja transcriptional profile, and identified three PPCK genes (GsPPCK1, GsPPCK2 and GsPPCK3) as potential alkali stress responsive genes. In this study, we confirmed the induced expression of GsPPCK3 under alkali stress and investigated its tissue expression specificity by using quantitative real-time PCR analysis. Then we ectopically expressed GsPPCK3 in Medicago sativa and found that GsPPCK3 overexpression improved plant alkali tolerance, as evidenced by lower levels of relative ion leakage and MDA content and higher levels of chlorophyll content and root activity. In this respect, we further co-transformed the GsPPCK3 and SCMRP genes into alfalfa, and demonstrated the increased alkali tolerance of GsPPCK3-SCMRP transgenic lines. Further investigation revealed that GsPPCK3-SCMRP co-overexpression promoted the PEPC activity, net photosynthetic rate and citric acid content of transgenic alfalfa under alkali stress. Moreover, we also observed the up-regulated expression of PEPC, CS (citrate synthase), H⁺-ATPase and NADP-ME genes in GsPPCK3-SCMRP transgenic alfalfa under alkali stress. As expected, we demonstrated that GsPPCK3-SCMRP transgenic lines displayed higher methionine content than wild type alfalfa. Taken together, results presented in this study supported the positive role of GsPPCK3 in plant response to alkali stress, and provided an effective way to simultaneously improve plant alkaline tolerance and methionine content, at least in legume crops.

Nutrient biofortification of food crops

Plant-based foods offer an array of nutrients that are essential for human nutrition and promote good health. However, the major staple crops of the world are often deficient in some of these nutrients. Traditional agricultural approaches can marginally enhance the nutritional value of some foods, but the advances in molecular biology are rapidly being exploited to engineer crops with enhanced key nutrients. Nutritional targets include elevated mineral content, improved fatty acid composition, increased amino acid levels, and heightened antioxidant levels. Unfortunately, in many cases the benefits of these "biofortified" crops to human nutrition have not been demonstrated.