'Designer' Corn Gene to Help Eyesight
News Apr 21, 2010
Rod Smith, , April 20, 2010 http://sl.farmonline.com.au/
DECREASING or increasing the function of a newly discovered gene in sweet corn appears to change the amount of vitamin A content created in digestion of the corn and has significant implications for reducing blindness and mortality in children in developing nations and macular degeneration in adults in the western world, according to Purdue University in West Lafayette, Indiana, USA.
The finding was made through a research collaboration led by Torbert Rocheford, an agronomy professor and holder of the Patterson Chair of Translational Genetics at Purdue, according to the news release. The finding involved the yellow corn that is familiar to consumers in most of the world and a dark orange corn that's popular in Asian and South American countries and in northern Italy, Purdue said.
The orange color comes from higher levels of carotenoids, especially beta-carotene, which is converted into vitamin A during digestion, Purdue said, explaining that Rocheford is using various selection techniques to create a darker orange color and improved lines of the orange corn.
Between 250,000 and 500,000 children - mostly in Africa and Southeast Asia - become blind each year because of a vitamin A deficiency, and half of those children die within one year, the announcement said, citing data from the World Health Organisation.
Rocheford said increasing beta-carotene levels in cereal grains such as corn is an economical and promising way to address such deficiencies in developing parts of the world. He said the gene beta-carotene hydroxylase 1 (crtR-B1) alters beta-carotene in corn in a way that decreases the creation of vitamin A through digestion.
This occurs through hydroxylation in which beta-carotene is converted into other carotenoids that can cut the amount of vitamin A created in half or even completely.
Accordingly, Rocheford said pulling back the activity of the crtR-B1 gene would decrease hydroxylation significantly and increase vitamin A formation to address blindness and deaths in affected children. He said work already is underway to move a favorable "weak allele" into breeding materials for corn. (An allele is a form of genetic material, i.e., a gene.)
Conversely, Rocheford said "strong alleles" that increase the activity of crtR-B1 and, therefore, the hydroxylation process create more zeaxanthin. Zeaxanthin is a micronutrient that protects against macular degeneration, which is the leading reason for blindness in people over 55 years old in developed nations, according to the American Macular Degeneration Foundation.
Rocheford said these findings are encouraging for addressing sight issues in both developed and developing countries. "It's like a designer gene," he said. "We can select one version for the (western) population to increase zeaxanthin and a different version to increase beta-carotene for the needs of the developing world."
Children who are genetically predisposed to overweight, due to common gene variants, can still lose weight by changing their diet and exercise habits. Around 750 children and adolescents with overweight or obesity undergoing lifestyle intervention participated in the study conducted by researchers from the University of Copenhagen and Holbæk Hospital.
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