www.checkbiotech.org ; www.raupp.info ; www.czu.cz

Papaya is an important fruit for the tropics, where it is used in both the
food and cosmetics industries, March 2006.

As a result, studies are on the way on the the papaya?s genome, in order
to identify candidate genes that may be used to improve the nutritional
quality of papaya through marker-assisted breeding or genetic engineering.
Luke C. Devitt and colleagues of the Queensland Agricultural Biotechnology
Center contribute their findings as they report the ?Discovery of genes
associated with fruit ripening in Carica papaya using expressed sequence
tags.? Their work appears in a recent issue of Plant Science.

To identify genes involved in papaya fruit ripening, researchers generated a
total of 1171 expressed sequence tags (ESTs) from clones of two independent
fruit cDNA libraries derived from yellow and red-fleshed fruit varieties.
ESTs are short DNA fragments of expressed genes. They have been used
extensively and effectively in a number of fruit species as a tool for rapid
gene discovery.

Researchers found that the most abundant gene sequences isolated were those
coding for the enzymes chitinase, which breaks down chitin;
1-aminocyclopropane-1-carboxylic acid (ACC) oxidase, which controls the
release of ethylene in plants; catalase, which breaks down harmful hydrogen
peroxide into hydrogen and water; and methionine synthase, which processes
amino acids. Researchers also found putative genes contributing to fruit
softening, among them cell wall hydrolases, cell membrane hydrolases, and
ethylene synthesis and regulation sequences. By comparing ESTs with gene
sequences in other plant species, researchers identified expressed papaya
genes which could play a role in fruit aroma and color.

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