BioUpdates for February, 2002

by Andrew Tolley

Gut Feelings: Not Always What You Think

OK Charales

Pass on the Salt

Nonbreaking News

Seals: No Longer Just a Circus Act

Gut Feelings: Not Always What You Think

Researchers from the Howard Hughes Medical Institute are busy digesting their discoveries concerning intestinal cell development and differentiation. Investigating the role of the Math1 gene in the development of neuronal cells, the team wanted to examine the role of this gene in the differentiation of intestinal neuronal cells. Using genetically engineered mice, the team was surprised by their discoveries. Contrary to their gut feeling, the team found no evidence of Math1 expression in the development of neuronal cells in the intestine. However, it was apparent that Math1 does have a role in the differentiation of three secretory cells. Goblet cells, enteroendocrine cells and Paneth cells all owe their development, at least in part, to Math1 genes. Subsequent investigation using mice engineered to lack Math1 confirmed the gene's role, as all three secretory cells were absent in these animals. Further study revealed that Math1-expressing cells give rise to secretory cells, and Math1-negative progenitor cells facilitate the development of enterocytes, the intestine's absorptive cells. Although much work has yet to be completed, this discovery not only sheds light on intestinal stem cell differentiation but also has great promise in clinical applications for gastrointestinal conditions.

References:

Qi, Yang et al (2001). Requirement of Math1 for Secretory Cell Lineage Commitment to the Mouse Intestine. Science 294 (Dec. 7): 2,155-2,158.

Visit:

Science

http://www.sciencemag.org/cgi/content/abstract/294/5549/2155

OK Charales

Documentary films and basic textbooks can sometimes make the history of life on Earth seem like a done deal. Morphing video images of organisms evolving, transforming from one thing to another, are guilty of oversimplification and can be misleading. Certainly, evolutionary biologists have a strong grasp on the course of life on Earth but many gaps remain to be filled. This is true of the evolution of land plants from their aquatic ancestors. The fossil record reveals that land plants emerged some 450 million years ago from algae but little more. A research team from the University of Maryland, by examining the gene sequences of freshwater algae, has been able to fill some of those gaps in our knowledge. The data of the research team confirms that a common green alga, the Charales, is the closest living relative of the first land plants and that they evolved from a common ancestor. Although the ancestor has yet to be identified in the fossil record, the team believes that genetic evidence is strong enough to make inferences about this plant's appearance. Charales has long been one of the leading contenders, but until this work other groups of algae, such as Coleochaetales with their similar physiology, also were likely candidates. However, the extensive DNA sequencing at the University of Maryland puts Charales on top.

References:

Karol, Kenneth G. et al (2001). The Closest Living Relatives of Land Plants. Science 294 (Dec. 14): 2,351-2,353.

Visit:

Science

http://www.sciencemag.org/cgi/content/abstract/294/5550/2351

Pass on the Salt

The inability of crops to tolerate high salt levels in the soil has always inhibited agriculture. Today, as the need for higher crop yields grows, over-irrigation of the land is intensifying the problems. Millions of acres of arable land are rendered unproductive as repeated cycles of irrigation salinize the soil. Despite extensive research concerning salt tolerance, little is understood about the key issue: How does sodium enter a plant in the first place? Researchers from Purdue University are beginning to unveil the mystery, which could lead horticulture to major advances in the development of salt-tolerant plants. Examining thousands of specimens of the wild mustard plant, Arabidopsis thaliana, the research team has identified a protein and one of the genes responsible for enabling sodium to enter plants. The discovery of a "double mutant" specimen that takes up less salt than normal plants provided the necessary clue. In this specimen, the gene that activates the protein AtHKT1 is disabled. However, further study demonstrated that plant growth still declined at higher salt concentrations, suggesting other genes also are involved in salt uptake. The discoveries of the Purdue team indicate that plants thriving in saline environments tolerate high sodium rather than avoid it. Understanding how they do this will be a key research area, as will identifying all the genes that activate AtHKT1. Learning how to disable these genes without compromising their other functions (which they surely must have, given that salt uptake offers plants no advantage) could be the key to opening up salt-laden soil to agriculture.

References:

Rus, Ana et al (2001). AtHKT1 is a salt tolerance determinant that controls Na+ entry into plant roots. Proceedings of the National Academy of Science 98 (Nov. 20): 14,150-14,155.

Visit:

Proceedings of the National Academy of Science

http://www.pnas.org/cgi/content/abstract/98/24/14150

Nonbreaking News

Researchers from Creighton University and the Genome Therapeutics Corporation recently published the results of research that represents one of the biggest breakthroughs in bone biology in the last few decades, and it could revolutionize the treatment of bone diseases such as osteoporosis. Prompted in 1995 by observations of a patient with very high bone density, Dr. Robert Recker and colleagues succeeded in identifying the first specific gene mutation that influences how much bone a body develops. Other genes associated with high bone mass are known, but they also are connected with some form of disease or abnormality. This gene mutation appears free of these problems; researchers believe this mutation may be involved in controlling the skeleton's "set point," a mechanism that controls the rate at which bone is built up or broken down. The set-point concept is a significant notion in broader biological thinking, but until this discovery it had not been concretely identified in any aspect of biology. This research, therefore, has implications beyond the team's specific interests, shedding light on regulatory set points in other mechanisms of the body. The researchers view their work as changing the thrust of osteoporosis treatment. Current treatments focus on halting or slowing bone loss-these results pave the way for approaches that can build new bone and reverse the effects of disease.

References:

Little, Randall D. et al (2002). A Mutation in the LDL Receptor Related Protein5 Gene Results in the Autosomal Dominant High-Bone-Mass Trait. American Journal of Human Genetics 70 (Jan.).

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American Journal of Human Genetics

http://www.journals.uchicago.edu/AJHG/journals/issues/v70n1/
013398/brief/013398.abstract.html

Seals: No Longer Just a Circus Act

Perhaps they were inspired by the "monkey-cam" segment on the David Letterman Show a few years ago when a chimpanzee equipped with a camera on its back raced around the studio, providing a unique viewing angle; then again, perhaps not. Nonetheless, a research team at McMurdo Station in Antarctica is employing a similar concept to gain insight into the behavior of two fish species: the Antarctic silverfish and the Antarctic toothfish. Exploiting the desire of the Weddell seal to eat these fish, the team equipped fifteen seals with video cameras, LEDs, and data recorders, enabling the researchers to track the seals and observe their interactions with their prey. As a result, a unique body of data has been trawled from the depths, causing some significant revisions to our understanding of these fish and the dynamics of marine ecosystems in the region. Although the "seal-cam" has its limitations, it does provide deeper insight into marine ecology than can be gleaned from the study of fish catches or the observations of intrusive human divers or boat-based cameras. The possibilities of such technology are tantalizing, as they may be adapted to a variety of land-based uses too.

References:

Fuiman, L. et al (2002). Behavior of midwater fishes under Antarctic ice: observations by a predator. Marine Biology Online Edition (Jan.).

Same article will appear in March 2002 print edition of Marine Biology.

Visit:

Marine Biology

http://link.springer.de/link/service/journals/00227/contents/
01/00752/s00227-001-0752-ych002.html