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  • From: "Lon J. Rombough" <lonrom@hevanet.com>
  • To: NAFEX <nafex@lists.ibiblio.org>
  • Subject: [NAFEX] FW: Papaya Sex-Chromosome Study
  • Date: Fri, 23 Jan 2004 14:18:25 -0800



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From: ARS News Service <NewsService@ars.usda.gov>
Reply-To: ARS News Service <NewsService@ars.usda.gov>
Date: Fri, 23 Jan 2004 13:10:58 -0500
To: ARS News subscriber <lonrom@hevanet.com>
Subject: Papaya Sex-Chromosome Study

STORY LEAD:
Papaya Sex-Chromosome Study Provides New Glimpse of Evolution

___________________________________________

ARS News Service
Agricultural Research Service, USDA
Marcia Wood, (301) 504-1662, MarciaWood@ars.usda.gov
January 23, 2004
___________________________________________

What do people and papayas have in common?

Both have specialized chromosomes carrying genes that determine the gender
of their offspring. These so-called "sex chromosomes" are markedly
different from ordinary chromosomes.

In the current issue of the journal Nature, scientists from industry,
university and the Agricultural Research Service provide the first direct
evidence that papaya sex chromosomes are evolving from other
chromosomes--ordinary ones in the plants' genetic makeup. The same process
is thought to have occurred in the human genome during the millions of
years of human sex chromosome evolution.

In humans, sex-chromosome studies may explain inheritance of gender-linked
conditions such as sickle-cell anemia or hemophilia. In papaya, studies of
sex chromosomes may help scientists understand inheritance of traits
responsible for the size, shape and quality of this popular tropical
fruit. Apparently, only papaya trees that inherit a specific combination
of genes on their sex chromosomes produce fruit that has the elongated
shape that consumers of Hawaii-grown papaya prefer. Today, just half of
all commercial papaya seedlings grown in Hawaii inherit this prized
combination of genes.

ARS research plant physiologist Paul H. Moore at Aiea, Hawaii, and ARS
research horticulturist Francis T.P. Zee at Hilo participated in the
papaya study. Both are with the ARS U.S. Pacific Basin Agricultural
Research Center. Plant molecular geneticist Ray Ming of the
grower-sponsored Hawaii Agriculture Research Center, Aiea, led the
investigation.

The scientists analyzed genetic material from more than 2,000 fresh
papayas. They found that a chromosome with a small region of genes for
male traits--comprising only about 10 percent of the chromosome's
length--determines sex in papaya. This papaya chromosome resembles a
primitive version of the human Y chromosome--perhaps as it existed 240 to
320 million years ago. The papaya research provides a unique opportunity
to examine the beginnings of sex chromosome evolution.

ARS is the U.S. Department of Agriculture's chief scientific research
agency.
___________________________________________

* This is one of the news reports that ARS Information distributes to
subscribers on weekdays.
* Start, stop or change an e-mail subscription at
www.ars.usda.gov/is/pr/subscribe.htm
* NewsService@ars.usda.gov | www.ars.usda.gov/news
* Phone (301) 504-1638 | fax (301) 504-1648






  • [NAFEX] FW: Papaya Sex-Chromosome Study, Lon J. Rombough, 01/23/2004

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