News from the World of Biology

First up, a new clue about the origin of angiosperms:

To Charles Darwin it was an ‘abominable mystery’ and it is a question which has continued to vex evolutionists to this day: when did flowering plants evolve and how did they come to dominate plant life on earth? A new study in Ecology Letters reveals the evolutionary trigger which led to early flowering plants gaining a major competitive advantage over rival species, leading to their subsequent boom and abundance.

The study, by Dr Tim Brodribb and Dr Taylor Field of the University of Tasmania and University of Tennessee, used plant physiology to reveal how flowering plants, including crops, were able to dominate land by evolving more efficient hydraulics, or ‘leaf plumbing’, to increase rates of photosynthesis.

“Flowering plants are the most abundant and ecologically successful group of plants on earth,” said Brodribb. “One reason for this dominance is the relatively high photosynthetic capacity of their leaves, but when and how this increased photosynthetic capacity evolved has been a mystery.”

Using measurements of leaf vein density and a linked hydraulic-photosynthesis model, Brodribb and Field reconstructed the evolution of leaf hydraulic capacity in seed plants. Their results revealed that an evolutionary transformation in the plumbing of angiosperm leaves pushed photosynthetic capacity to new heights.

It will be interesting to track down the molecular machinery involved in the development of this “leaf plumbing,” as front-loading would lead us to expect that it existed prior to the development of angiosperms.

Next up, another example of the way cells facilitate their own evolution:

Like savvy Wall Street money managers, bacteria hedge their bets to increase their chances of survival in uncertain times, strategically investing their biological resources to weather unpredictable environments.

In a new study available online and featured on the cover of Cell, UT Southwestern Medical Center researchers describe how bacteria play the market so well. Inside each bacterial cell are so-called genetic circuits that provide specific survival skills. Within the bacteria population, these genetic circuits generate so much diversity that the population as a whole is more tolerant of — and is more likely to survive — a wide range of variability in the environment.

“We have found that a particular genetic circuit is responsible for generating diversity within the bacteria population,” said senior author Dr. Gürol Süel, assistant professor of pharmacology and in the Cecil H. and Ida Green Comprehensive Center for Molecular, Computational and Systems Biology at UT Southwestern.

This diversity, like a diversified investment portfolio, means that each bacterium has characteristics that allow it to survive under certain conditions, said Dr. Süel. “When conditions are highly variable, some individual bacteria are equipped to thrive in the highs or lows, while others tank,” he said. “It’s like the stock market. If you invest all your money in just one stock, and conditions change to lessen or completely eliminate its value, you won’t survive financially. Similarly, in the case of these bacteria, if all the cells were adapted to only a small, rigid set of environmental factors, the population would be wiped out if conditions unexpectedly changed.

[….]

Biological “noise” in the genetic circuit, which comes from random fluctuations in the chemical reactions involved in the pattern of interactions, is similar to the undesirable noise — like static heard on AM radio — found in electrical circuits. In biological systems, however, biochemical “noise” is beneficial. In fact, it is the root mechanism that drives diversity within the bacteria population. Dr. Süel previously found that when noise reaches a certain level in some genetic circuits, it can prompt cells to transform from one cellular state to another.

For the current study, the researchers went beyond studying the native genetic circuit. Just as electronic maps can find alternate routes between two points, the UT Southwestern researchers also developed an alternative, synthetic genetic circuit that used a different architecture — or route — to accomplish the same function as the native circuit.

Dr. Süel believes his group is the first to insert such a synthetic genetic circuit into living bacterium and show that it can replace the biological function of the native version. He said his team was surprised to find that the behavior of the synthetic circuit was most precise, essentially generating less noise. The result was a population less diverse than the natural one. They were even more surprised to find that the lack of precision — or greater noisiness — in the native circuit ultimately allows bacteria to survive in a wider range of environments.

“It turns out that sometimes being sloppy can be good,” Dr. Süel said. “For these bacteria, the more variable they are, the better they will be able to perform because they can adapt to a wider range of environments.”

Two major take-home points from this study.

First, this is another example showing the manner in which evolution is indebted to factors that are intrinsic to life (I think the summary above speaks for itself).  I’ve been meaning to talk about similar studies that make the same point since posting this entry.

Second, note that the “sloppy” circuit is actually a better design than the more precise circuit, as the “sloppy” circuit is better able to exploit noise to impose control.  This is major theme that should be remembered anytime someone argues against design simply because the system appears wasteful.  Cells exist with an eye toward the future and that “waste” is a key to getting there.

Lastly, we have this:

Time-lapsed video of individual breast tissue cells reveals a never-before-seen event in the life of a cell: a protein that cycles between two major compartments in the cell. The results give researchers a more complete view of the internal signals that cause breast tissue cells to grow, events that go awry in cancer and are targets of drug development.

The protein ERK, which helps cells respond to growth factors, travels back and forth between the nucleus, where genes are turned on and off, and the cell proper, where proteins work together to keep the cell functioning. In the video, individual cells pulsate with green light as an engineered fluorescent ERK fills the nucleus, exits and re-enters again in cycles that take about 15 minutes. The researchers don’t know if the oscillation affects the activity of other proteins in a regulatory fashion, they report in December 1 issue of Molecular Systems Biology, but find the oscillations to be regular and robust.

This is just cool and nods to life as carbon-based nanotechnology.  In fact, you can watch of a video of these oscillations (seen as the blinking nuclei).  I should mention it is not true that this is “a never-before-seen event in the life of a cell.”  In some rod-shaped bacteria, certain proteins oscillate back-and-forth between ends and this behavior is plugged into cell division.  Something else to write about.

Is there anything more interesting than Life?

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