The new analysis revealed that papaya has fewer functional genes than any other flowering plant for which genome sequence is available. Its allotment of genes for key enzymes also differs significantly from its counterparts. Papaya contains more genes for enzymes involved in cell-wall expansion and starch production than Arabidopsis does. Papaya also contains more genes for volatile compounds, the odors that attract pollinators and animals that eat the fruit and disperse its seeds.
The number of genes dedicated to lignin synthesis in papaya is intermediate between that of poplar, which contains more such genes, and Arabidopsis, which has fewer. This makes sense, Ming said, because papaya is evolving from an herbaceous plant into a woody tree.
Papaya was introduced to Hawaii in the 1800s, and the production of papaya in Hawaii grew into a major industry. That industry faced a crisis in 1992, however, when the papaya ringspot virus (PRSV) was first identified in Puna, the center of Hawaiian papaya production.
PRSV affects papaya production throughout the world. The virus interferes with the plants ability to photosynthesize. Affected plants are stunted and often produce deformed and inedible fruit. Papaya production in Hawaii dropped from 55.8 million pounds to 35.6 million pounds between 1992 and 1998 as a result of the virus.
Using a technique developed in 1986 that involved randomly inserting a viral coat protein gene into a plant to give the plant immunity to the virus, in the early 1990s scientists at Cornell and the University of Hawaii (led by Dennis Gonsalves, who is now director of the USDAs U.S. Pacific Basin Agricultural Research Center) developed a transgenic papaya that was resistant to PRSV. The new study has found that the transgenic insertions occurred in only three pla
|Contact: Diana Yates|
University of Illinois at Urbana-Champaign