News

India's high-protein GM potato

K. S. Jayaraman

doi:10.1038/nindia.2010.127 Published online 21 September 2010

The humble potato now has a high-protein avatar.

Scientists at the National Institute for Plant Genome Research (NIPGR) in New Delhi are planning to seek regulatory approval for commercial cultivation of a high protein potato that they have developed through genetic modification.

Nick named 'protato' the protein packed genetically modified (GM) potato contains 60 per cent more protein than a wild-type potato and has increased levels of several amino acids.

More than a billion people worldwide consume potatoes on a daily basis but unfortunately, the nutritional quality of potato tubers is greatly compromised because they contain less protein and are deficient in lysine, tyrosine, and the sulfur-containing amino acids.

"While the international effort is to enhance the starch quality in potato through transgenic approach the Indian effort has been to increase the protein quality and quantity," says Govindarajan Padmanabhan, well known biochemist at the Indian Institute of Science who is familiar with the Indian research on protato. Asis Datta and his group at NIPGR have been on this effort for over 15 years.

The NIPGR researchers say that efforts worldwide during the last decade to improve protein quality and quantity in crop plants has had limited success. This is because introduction of new genes in target plants often resulted in an increase in one of the amino acids at the expense of others, leading to an imbalance of the amino acid profile in transgenic crops. The AmA1 (Amaranth Albumin 1) gene from Grain Amaranthus, an edible plant, chosen by the NIPGR group was, however, an exception. Eight years ago Datta's group had succeeded in developing transgenic potato containing the AmA1 gene that resulted in an increase in protein content by about 30 per cent.

In the present study, Datta's colleague Subhra Chakraborti and co-workers claim to have increased the protein content by around 60 per cent. "Commercial varieties are ready and would be submitted to the Genetic Engineering Appraisal Committee (GEAC) now," Datta told Nature India.

"The AmA1 has great agricultural importance because it is a well balanced protein in terms of amino acid composition possessing even better values than recommended by the World Health Organization for a nutritionally rich protein," Datta explained. More importantly, because it is a non-allergenic protein that originated from an edible crop, the transgenic crops expressing AmA1 would have greater acceptability, says Datta. "Therefore, our strategy of transferring AmA1 gene to crop plants may prove to be more acceptable to the general public than currently used GM crops."

In their latest study, the NIPGR scientists used a tuber-specific promoter, leading to maximum expression of the protein in the tuber. Analyses of the transgenic tubers revealed there was a 35–60 per cent increase in total protein content "one of the highest increases observed in any transgenic crop," the report said. Besides, they reported an increase in the essential amino acids such as lysine and sulfur amino acids, generally deficient in plant proteins, and also an increase in aspartic acid, glutamic acid, arginine, leucine, and isoleucine levels. On average, the increases in biomass ranged from 7–20 per cent.

"These results are striking because this genetic manipulation also resulted in a moderate increase in tuber yield," the report said. The transgenic potato was found to be safe in terms of health requirements, without compromising on palatability and cooking qualities. Long-term oral feeding for 90 days did not show any detectable clinical and histopathological changes or observable toxic effects in animals tested. The transgenic tubers did not evoke any allergenic response in the animals. "Altogether, these results showed that the expression of AmA1 is a potential strategy for the nutritional improvement of food crops," the researchers concluded.

Padmanabhan agrees. "It is a great opportunity for India to release this transgenic potato for commercialization, subject to all the necessary clearances required by the Genetic Engineering Appraisal Committee," he told Nature India. "This product should be treated as an improved variety of potato with better yields and protein quality. This will set a precedence to focus on GM technology to improve nutritive quality of food, a dire need for a developing country like India."

Padmanabhan said that potato per se may not satisfy the protein deficit, since the absolute increase in protein content is between 0.9 and 1.3 per cent (on dry weight basis). "But, as the authors indicate, the study has identified AmA1 protein as the choice for improving protein quality and quantity in next generation crops and if this can happen with rice, ensuring higher content of lysine and sulfur amino acids, it will create a revolution."

Not everyone is convinced though. "It (GM potato) is a completely objectionable wastage of public funds," says Kavitha Kuruganti of Kheti Virasat Mission, a Punjab-based NGO. A much smarter option would be to spread the cultivation of Grain Amaranthus itself rather than putting a gene from that plant into potato, she told Nature India. Datta however argues that Grain Amaranthus growth as well as land requirement are major handicaps for its cultivation as a food crop. "Moreover," he says, "the same AmA1 gene can be used for the improvement of other crops as well."


References

  1. Chakraborty, S. et al. Next generation protein-rich potato by expressing a seed protein gene AmA1 as a result of proteome rebalancing in transgenic tuber. doi: 10.1073/pnas.1006265107 (2010)