Monday, February 19, 2007

 

Michigan Researcher Hopes to Unlock Evolutionary Secrets

Roughly 2 1/2 billion years ago, some algae began to photosynthesize, an astonishing development that led to the creation of plants and a myriad of complex life forms, including, incidentally, mankind.

Today, Eric Linton, a Central Michigan University assistant professor of biology, is studying the gene makeup of single-celled euglenoids - single-celled organisms that acquired the ability to photosynthesize from algae - to learn whether that evolutionary step was a single hallmark moment or a series of events over time.

Eventually, Linton hopes to learn whether dormant genes that once controlled photosynthesis in certain euglenoids can reactivate, shedding light on whether scientists can jumpstart long-dormant genes in other organisms, such as in humans to fight a host of diseases.

With a 354,000 dollar grant from the National Science Foundation, Linton has begun a three-year project to perform complete genome sequencing of six forms of euglenoids, some of which long ago lost the ability to photosynthesize.

A focus of Linton's research is chloroplasts - components of euglenoid cells that serve as an engine for photosynthesis, or the synthesis of sugar from light, carbon dioxide and water. Some of the euglenoids under study have functioning chloroplasts, enabling photosynthesis; in others, the chloroplasts apparently are dormant.

By examining the genes for chloroplasts from six different euglenoids, Linton hopes to learn whether all acquired the ability to photosynthesize from the same ancestor, or multiple ancestors. Also, Linton wants to deduce how the genes are transferred, lost or evolved when two genomes are combined.

The discovery of supposedly dormant genes in the euglenoids raises questions about whether such genes - both in euglenoids and humans - can receive a man-made jump-start one day.

"If they are keeping these genes around," Linton said, "they must be achieving something."

Most genome sequencing will occur off-campus, but Linton plans on using a 50,000 dollar differential interference contrast microscope - which provides near 3D imaging - for much of the study. A graduate student and two undergraduates will assist him.

Linton, who joined CMU in July 2006, earned his doctorate in 2000 from Rutgers University in New Jersey.

Source: Central Michigan University PR January 31, 2007

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An earlier paper co-authored by Eric Linton:

Pattern of diversity in the genomic region near the maize domestication gene tb1

Richard M. Clark, Eric Linton, Joachim Messing, and John F. Doebley

PNAS | January 20, 2004 | vol. 101 | no. 3 | 700-707

Domesticated maize and its wild ancestor (teosinte) differ strikingly in morphology and afford an opportunity to examine the connection between strong selection and diversity in a major crop species. The tb1 gene largely controls the increase in apical dominance in maize relative to teosinte, and a region of the tb1 locus 5' to the transcript sequence was a target of selection during maize domestication. To better characterize the impact of selection at a major "domestication" locus, we have sequenced the upstream tb1 genomic region and systematically sampled nucleotide diversity for sites located as far as 163 kb upstream to tb1. Our analyses define a selective sweep of {approx}60-90 kb 5' to the tb1 transcribed sequence. The selected region harbors a mixture of unique sequences and large repetitive elements, but it contains no predicted genes. Diversity at the nearest 5' gene to tb1 is typical of that for neutral maize loci, indicating that selection at tb1 has had a minimal impact on the surrounding chromosomal region. Our data also show low intergenic linkage disequilibrium in the region and suggest that selection has had a minor role in shaping the pattern of linkage disequilibrium that is observed. Finally, our data raise the possibility that maize-like tb1 haplotypes are present in extant teosinte populations, and our findings also suggest a model of tb1 gene regulation that differs from traditional views of how plant gene expression is controlled.

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Recent posts include:

"Rafflesiaceae: Family found for gigantic flowers"

"Carnal Knowledge: How we evolved into male and female"

"Microbes: Learning to live with oxygen on early Earth"

"Hail to the Hornworts: New Plant Family Tree Sheds Light on Evolution of Life Cycles"

"Rare Evolutionary Example Of 'Recent' Embosymbiont Offers Clues To How Plants Came To Be"

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