RedDetect

As I mentioned today the global landmine problem is getting worse, not better. Currently landmines are being planted at a rate 25x greater than they are being cleared. According to the UN, even if no more landmines were planted ever again it would take over 1100 years to remove all the mines that are currently in place using present day technology.

Although innovative programs like the HeroRats organization can greatly speed up demining, there is a clear need for multiple tools to manage the growing problem. The Nitrogen dioxide detecting plants, RedDetect, I mentioned in class are now being developed by Aresa - a non-profit organization in Wallonia, a part of Belgium. Although Arabidopsis plants were originally used it was decided that, although they grow quickly, they were not visible enough from a distance (kind of important if you want to stand well back). Therefore the same technqiue has been applied to tobacco plants. The tobacco plant was chosen as it is known to grow well in a wide range of environmental conditions and any changes in colour can easily be seen because of its large leaves. The tobacco plants were transformed in the same way as the Arabidopsis with an activation gene from the snapdragon plant, which enables them to detect nitrogen dioxide, a by-product of landmines, in contaminated soil. This releases anthocyanin, a natural red plant pigment, into the leaves.

As of April 2009 the plants have already been successfully tested in laboratories and greenhouses and are now undergoing field trials in Serbia and South Africa. The plants only detect the mines of course, someone still needs to physically remove them...

One of the guys that took us into the minefield has stepped on 6 landmines. The first landmine blew off his foot. The next landmine took off half his leg. The next 4 blew his prosthetic leg to pieces, and he hopped down to the NGO for a replacement. Yet, he keeps going back into the minefields to illegally cut down trees that he can sell to the Thais for $5 a piece. This is how he feeds his family. And that is the life of a village de-miner.
From Adam Katz's blog entry about a visit to a Cambodian minefield.

Double fertilization – caught in the act

There was an article in Trends in Plant Science last year called Double fertilization – caught in the act that both reviews the field and includes photographs of Arabidopsis plants caught in the act....

In flowering plants, fertilization is unique because it involves two pairs of male and female gametes, a process known as double fertilization. Here, we provide an overview of the field and a detailed review of the outstanding recent advances, including in vivo imaging of double fertilization and the identification of a signaling pathway controlling the release of the male gametes and of a protein involved in gamete membrane fusion. These recent results are stepping stones for further research; our knowledge of double fertilization is expanding as newly discovered molecular pathways are explored and new mutants are characterized. Controlling plant fertilization is essential for seed production, and molecular understanding of double fertilization will provide the tools to improve crops and breeding programs.

Birth Dating Human Cells

How can scientists determine the age of human cells? How frequently are human cells replaced, if at all?

In 2005 scientists hit upon an ingenious method that takes advantage of a dark period in recent world history - the above-ground testing of nuclear weapons between the mid-1950s and 1963. Nuclear weapons testing resulted in a sharp spike in carbon-14 levels worldwide. The levels peaked in 1967 and have since declined as carbon-14 diffused and equilibrated with the atmosphere, the oceans, and the biosphere. Carbon is incorporated into the chemical components of all new cells, of course, including DNA. It turns out that the carbon-14 levels in nuclear DNA correspond very closely to the atmospheric levels at the time the DNA was synthesized. So by comparing the cells’ nuclear DNA carbon-14 levels to a chart of atmospheric cabon-14 levels each year, one can determine the cells’ birth date.

How does this help us determine cell turnover? Think about it: if all of the cells in a piece of tissue are the same age as the individual, then cells are not being replaced throughout life. But if the average cell age is much younger than the individual, then cell turnover must be relatively high. The scientists who developed the cell-dating technique report that neurons in the cerebral cortex (the most highly developed area of the brain) do not undergo significant replacement throughout life - you’re born with all the cortical brainpower you’re ever going to have. In contrast, cells lining the intestine are replaced frequently.

Reference: "Retrospective Birth Dating of Cells in Humans". Cell 122:133-143, 2005.

Costs of changing sex

In class we looked at certain monoecious plants that are able to change sex as they grow - and at an explanation for why this should occur and why the change should always be from male to female. A few animals can also do this sequential hermaphroditism but it is relatively rare as a strategy. In a recent paper in Am Nat two Yale scientists ask why the strategy isn't more common. One explanation would be that the costs of changing sex outweigh the benefits. The conclusions of their study are not buried deep in the paper but right there in the title:
Costs of Changing Sex Do Not Explain Why Sequential Hermaphroditism Is Rare

The RR Warner in the acknowledgements and numerous citations is, of course, UCSB's Bob Warner who works, amongst other things, on sequential hermaphroditism in fish

Also, if you'd like to read the original Nature paper describing the Papaya story I mentioned you can find it here:
A primitive Y chromosome in papaya marks incipient sex chromosome evolution

Extreme longevity in proteinaceous deep-sea corals

From last week's PNAS (Proceedings of the National Academy of Sciences):
Extreme longevity in proteinaceous deep-sea corals

The "gold coral" Gerardia and the black coral Leiopathes both grow several meters tall at depths of up to 500 meters on the Hawaiian seabed. They grow when each succeeding coral polyp secretes a thin layer of calcium carbonate onto the base of the "cups" in which they live.

Previous studies had guessed their age at a few hundred years but the PNAS study by Brendan Roark and colleagues argues that what were previously counted as annual growth rings actually take much longer to form. Using high-resolution radiocarbon dating, Roark's team studied the corals' outermost shell for traces of "bomb carbon" - radioactive carbon produced during nuclear tests in the 1950s. They found it was present in only the upper 10 micrometres of the coral skeleton, suggesting this tiny slice took decades to build up. Further carbon dating of layers down at the corals' base revealed the oldest Gerardia to be about 2742 years old and the Leiopathes 4265 years old.

Restoration Seminar Series

Spring seminar series on Channel Island Restoration
Monday nights: 6-7pm, CCBER: Harder South, Rm 1013.

This series is supported in part by the students of UCSB through the
Coastal Fund.


March 30th : Chris Still (UCSB Geography): Setting the Stage:
Background Geography of Channel Islands

April 6: Brad Keitt (Island Conservation): Protecting seabird
biodiversity by conserving islands: an integrated regional approach

April 13: Ken Owen & Duke McPherson (Channel Islands Restoration):
Invasive Plant Control on the Channel Islands
   (Followed by pizza and discussion)

April 20^th : Kathryn McEachern (USGS): Rare Plant Research and
Restoration: California Channel Islands

April 27^th : Emily Howe (SERG, SDSU): Restoration on San Clemente Island

May 4^th : Lisa Stratton (CCBER): Limiting Factors to Oak Restoration
on Santa Catalina Island

May 11:  Sarah Chaney (NPS Channel Islands):  Weed Control and
Restoration on Anacapa Island

May 18^th : Steve Junak (Santa Barbara Botanic Garden): Rare Plant
Recovery on San Clemente Island
(Followed by snacks and discussion)

June 1: Final Discussion

Two Seminars

"The effects of male-male competition and the costs of resource acquisition on honest sexual signaling in Great Bowerbirds (Chlamydera nuchalis)."
Natalie R. Doerr PhD seminar

Wednesday, April 1, 2009 at 4:00pm Horvath Conference Room, Bio Sci 2 Bldg, Rm 6141
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"Climate change and aquatic ecosystems on the west coast: Can we forecast responses and prepare for impacts?"
Daniel Schindler, University of Washington

Monday, April 6th, MSI Auditorium

Daniel is a broad community ecologist. However, he perhaps best known for his research looking at how climate change impacts fisheries, with an emphasis on salmon populations in Alaska.
From his website: My current research activities are focused generally on understanding the causes and consequences of dynamics in aquatic ecosystems. Of particular interest are (1) the effects of changing climate on trophic interactions and ecosystem services provided by aquatic ecosystems, (2) fisheries as large-scale drivers of ecosystem organization, (3) importance of anadromous fishes for linking marine ecosystems to coastal aquatic and riparian systems, and (4) the importance of aquatic-terrestrial coupling in the organization of aquatic ecosystems.