Navigation Links
Researchers peek at the early evolution of sex chromosomes
Date:8/6/2012

CHAMPAIGN, Ill. Two new studies offer insight into sex chromosome evolution by focusing on papaya, a multimillion dollar crop plant with a sexual problem (as far as growers are concerned) and a complicated past. The findings are described in two papers in the Proceedings of the National Academy of Sciences.

The research reveals that the papaya sex chromosomes have undergone dramatic changes in their short evolutionary histories (they are about 7 million years old; by comparison, human sex chromosomes began their evolution more than 167 million years ago). One of the two studies compares the papaya X chromosome with that of a closely related non-sex chromosome (called an autosome) in a sister species. The other looks at differences between the X and Y chromosomes.

The studies show that the papaya sex chromosomes are increasing in size mostly through the accumulation of repetitive sequences while also reorganizing themselves and losing some genes carried over from their days as autosomes. Some of the lost genes are gone without a trace, while other remnants of genes that are no longer functional called "pseudogenes" are still present. The papaya Y chromosome also has independently gained some genes from the autosomes, the researchers report.

Gene loss in the Y chromosome is well documented in ancient Y chromosomes, but gene loss in the X chromosome, particularly at this early stage, is unexpected, as is the expansion of the X chromosome, said University of Illinois plant biology professor Ray Ming, who led both studies.

"The pace of gaining repetitive sequences and losing genes is faster in the Y than in the X chromosome, however," he said.

"This is the first look at an early stage of sex chromosome evolution," said Andrea Gschwend, who conducted the research with Ming while she was a doctoral student in his lab. "Usually people will focus on the ancient sex chromosomes because they are the most relevant to us," she said. "So this is the first direct and complete look at a more recently evolved sex chromosome system."

Analyzing the X chromosome is vital to understanding the evolution of sex, said Ming, an affiliate of the Institute for Genomic Biology at Illinois. The new findings in papaya suggest that the human X chromosome, too, has undergone numerous changes since it first distinguished itself from the autosomes, Ming said. Such changes are not detectable because the ancestral autosomes are no longer available for comparison, he said.

Because the papaya sex chromosomes are young and can be compared to closely related autosomes in a sister species, they offer a view of the early events of both X and Y chromosome evolution, Ming said.

Studying papaya sex chromosomes is a complicated task, however. The papaya has male, female and hermaphrodite sexual types, with two kinds of Y chromosomes (the male Y and the slightly modified, hermaphrodite Yh). Papaya plants may produce combinations of male and female (from the XY system) or hermaphrodite and female (from the XYh system) plants.

This complexity causes problems for papaya growers, Ming said. Hermaphrodites are the most productive of the papaya sexual types and yield the best fruit, but the offspring of hermaphrodites are not all hermaphrodites. To aid growers, Ming and his colleagues aim to develop a "true-breeding" hermaphrodite papaya variety that consistently produces hermaphrodite offspring.

When the researchers compared the X chromosome and the hermaphrodite Yh chromosome, they discovered that two major sequence inversions in the sex-determining regions of the Yh had taken place. One of these inversions occurred about 7 million years ago, and led the sex chromosomes and the autosomes down very different evolutionary paths, Ming said. The second inversion occurred about 1.9 million years ago and led to further differentiation between them. Each inversion has also undergone numerous sequence rearrangements, he said.

All of the findings are significant and useful, Ming said, but the X chromosome, which is generally overlooked in models of sex chromosome evolution, offered the most surprises.

"These studies are changing our view of sex chromosome evolution, particularly X chromosome evolution," he said. "We now know that both the X and Y chromosomes are dynamic in the early stages of their evolution, not only the Y chromosome, as previously thought."


'/>"/>
Contact: Diana Yates, Life Sciences Editor
diya@illinois.edu
217-333-5802
University of Illinois at Urbana-Champaign
Source:Eurekalert  

Related biology technology :

1. SRI International Researchers Developing Bioadhesive Gel to Protect Women from HIV and HSV Infections
2. Researchers create highly conductive and elastic conductors using silver nanowires
3. Researchers create rubber-band electronics
4. Cedars-Sinai researchers, with stem cells and global colleagues, develop Huntingtons research tool
5. Penn researchers study of phase change materials could lead to better computer memory
6. Researchers tune the strain in graphene drumheads to create quantum dots
7. WHEATON® Introduces a New Web Community for Scientists, Researchers, and Biopharmaceutical Packagers
8. Stevenage Bioscience Catalyst to Welcome Cambridge University Researchers
9. Syracuse University researchers use nanotechnology to harness power of fireflies
10. Researchers discover hereditary enzyme deficiency
11. JCVI Researchers, as Part of NIH Human Microbiome Project Consortium, Publish Papers Detailing the Variety and Abundance of Microbes Living on and in the Human Body
Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
Researchers peek at the early evolution of sex chromosomes
(Date:8/17/2017)... Village, CA (PRWEB) , ... August 17, 2017 ... ... technology for cancer research and personalized medicine, today announced the launch of a ... Kansas City, Missouri. The study’s goal is to evaluate the potential for early ...
(Date:8/16/2017)... ... August 16, 2017 , ... Today, 3Bar Biologics Inc ... $2M in funding from an impressive group of investors, including Rev1 Ventures, Maumee ... With this investment, 3Bar is broadening availability of its groundbreaking offering that uses ...
(Date:8/15/2017)... Charlotte, NC (PRWEB) , ... August 15, 2017 , ... ... in 2017, celebrating 10 years of successes helping medical technology companies and inventors develop ... company to a renowned full-service national engineering firm with a portfolio of clients in ...
(Date:8/15/2017)... , ... August 15, 2017 , ... The Conference ... on Immuno-Oncology 360° (IO360°) programming through a series of upcoming panels and events. The ... 7-9, 2018, at The Roosevelt Hotel in New York City. , “With our experience ...
Breaking Biology Technology:
(Date:3/30/2017)... The research team of The Hong Kong Polytechnic University (PolyU) ... ground breaking 3D fingerprint minutiae recovery and matching technology, pushing contactless ... use in identification, crime investigation, immigration control, security of access and ... ... A research team led by Dr Ajay Kumar ...
(Date:3/28/2017)... 2017 The report "Video Surveillance ... Servers, Storage Devices), Software (Video Analytics, VMS), and Service ... Forecast to 2022", published by MarketsandMarkets, the market was ... projected to reach USD 75.64 Billion by 2022, at ... base year considered for the study is 2016 and ...
(Date:3/24/2017)... Research and Markets has announced the addition of the ... Industry Forecast to 2025" report to their offering. ... The Global Biometric Vehicle Access ... 15.1% over the next decade to reach approximately $1,580 million by ... and forecasts for all the given segments on global as well ...
Breaking Biology News(10 mins):