Plastic fruits

Not GM, but no guarantee of their safety either

By Shrutika Mathur
Published: Monday 15 March 2010

imageWhile GM crops continue to hit headlines over safety and impact on biodiversity, genetically fine-tuned tomatoes enter the news with a difference.

Natural ripening and softening of fruits and vegetables lead to losses in harvest. For India, the second largest producer of fruits and vegetables, the loss is considerable. A study proposed a new approach at modifying the plants to increase shelf-life. This research by the National Institute of Plant Genome Research in New Delhi is the recent in line of several that failed to bring in desired results in the past.
Flavr Savr, the genetically modified tomato was developed in 1980s by scientists at Calgene Inc., a biotech company in the US. It was not supposed to soften while ripening naturally. The introduced genes maintained the fruit’s colour but it still turned soft. The new study explains increasing the shelf life of tomatoes on the same lines as Flavr Savr—by suppressing cell wall degradation. But instead of expresses foreign genes, the study silences ones that express enzymes during softening. Under the effect of the ripening hormone, ethylene, enzymes a -mannosidase and b -D-N-acetylhexosaminidase break down N-glycoprotein, a cell wall component. Free N-glycans are produced to soften the fruit.

“We show that suppression of the two enzymes enhances fruit shelf life, owing to the reduced rate of softening. Analysis revealed 2.5 times firmer fruits,” the researchers wrote. The tomatoes retained their firmness for 45 days unlike the normal tomatoes that start spoiling in 15 days. Suppression had no negative effect on growth, fruit development or seed production. The same enzymes are present in other fruits like papayas, bananas and mangoes.

The reason for apprehension over BT crops is the introduction of a foreign gene—nobody knows how it will respond to evolution. Although the new product is based on tweaking genes native to the plant, its effect on biodiversity is still unknown. So is the impact on the human system. Stories about Flavr Savr leading to stomach lesions had surfaced but were not proved.

“We have ensured that problems associated with GM food are not there in the tomato,” said Asis Datta, who led the study. But Arif Ali, head of the department of Biotechnology at Jamia Millia Islamia in New Delhi said: “Before introducing such crops in the market, their threat to biodiversity must be ascertained.”

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