A broad collaboration of research institutions in the U.S. and China has produced a first draft of the papaya genome. This draft, which spells out more than 90 percent of the plants gene coding sequence, sheds new light on the evolution of flowering plants. And because it involves a genetically modified plant, the newly sequenced papaya genome offers the most detailed picture yet of the genetic changes that make the plant resistant to the papaya ringspot virus.
The findings appear as the cover article in the journal Nature.
Papaya is now the fifth angiosperm (flowering plant) for which detailed genome information is available. The others are Arabidopsis (a well-studied member of the mustard family that includes species such as cabbage and radish), rice, poplar and grape.
One of the implications of this study is, on a larger scale, to understand the genome evolution of angiosperms, said Ray Ming, a University of Illinois professor of plant biology and co-lead author on the study.
The new findings indicate that the papaya genome took a different evolutionary path after its divergence from that of Arabidopsis about 72 million years ago, Ming said. Arabidopsis underwent two duplications of its entire genome in its recent evolutionary past, he said. These duplications, called alpha and beta, are not shared by papaya or grape. A much earlier triplication of the genome, called gamma, that is estimated to have occurred some 120 million years ago, is shared by all four eudicot plants Arabidopsis, poplar, grape and papaya for which genome sequences are available.
Papaya is one of the most nutritious fruits known. Its melon-like flesh is high in provitamin A, vitamin C, flavonoids, folate, pantothenic acid, potassium, magnesium and fiber.
The papaya plant also produces papain, a digestive enzyme that is used in brewing, meat tenderizing, and in some cosmetics and pharmaceutical products. Today it is culti
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University of Illinois at Urbana-Champaign