Frontiers Of Biology

Predicting Photosynthesis Evolution

Rice for All: Predicting C4 Photosynthesis Evolution
Evolution is important, yet, we cannot predict it. Evolution spans much more than just microevolution, or changes in allelic frequency within a gene pool from generation to generation. Evolution also acts on on the macro-level. It is here at the multicellular, macroevolutionary level, that we need help in explaining evolution.

Predicting Photosynthesis Evolution

Predicting paths in macroevolution is easy. A unique roadblock to predicting macroevolution is fitness, because it is the nominal currency of evolution. Fitness is a man-made concept. Consequently, we need to correlate fitness with other more explicitly empirical observations. In addition, to verify macroevolutionary hypotheses requires either a immense amount of time or a in silico model. Heckmann et al. decided to create a model for their evolutionary pathway: C3-to-C4 evolution. Their model needed to be dynamic; it needed to link genetic change to large phenotypic changes. They accomplished this modeling by defining variables that affected C4 character. Fluctuating these variables using Monte Carlo simulations, they found the pathways which led to C3-to-C4 evolution.

With enough knowledge about the C3-to-C4 process, we can streamline plant productivity by altering C3 plants such as rice into C4 plants. David Heckmann suggests that conversion of rice into a C4 plant is not only rational, but also feasible. David Heckmann outlines clear, logical steps to tackle this problem and, after reading his paper, I agree. I interviewed David Heckman, who is a fast-track Ph.D. working at the Heinrich Heine University of Düsseldorf. He received his bachelors in biology from the University of Cologne.This figure shows the path of C3-to-C4 evolution along a greedy pathway.

What do you make of being a scientist in central Europe and the E.U.? Advantages? Disadvantages?

Well in Germany the strict laws and public opinion against GMOs are a huge problem. Another problem comes from the job policy at German universities. Permanent positions in science are virtually unavailable, you are forced to become a group-leader if you want a permanent position.

We know what field of science you find interesting. But, what field of science, if any, un-interests you the most?

I have a hard time enjoying talks on developmental biology. Although I find the questions fascinating, I’m never satisfied with the answers…

Do you believe in the particular consensus that humans may have stopped evolving?

Well of course they haven’t stopped evolving. I don’t even think that’s possible for a replicating system.

Were there any setbacks during your research? (i.e. reciprocal sign epistasis, etc.)
I started modelling the system by a completely different approach that didn’t work at all. I also work in a group that’s not focussed on plant biology, that made it hard to develop the project.

My understanding of Monte Carlo simulations (and by extension random walk theory) is that they show many (if not all) of the possible pathways from a point of origin given a set of parameters. How is it possible that we are able to apply this to evolution, a process in which we have observed only once? Or, how are we able to infer different paths of evolution given that we only know of one?

I see the result of the Monte Carlo simulation as a probability density function that maps parameter combinations to probabilities. The Flaveria species probably represent two independent trajectories (see McKown 2005), while Moricandia and Panicum represent one each. Of course it would be great to have more data, but for now we have to work with what’s available.
What do you make of the International Rice Research Institute’s C4 Rice project?

I think we can learn a lot from this project, although an actual increase in yield will be very difficult to attain. I don’t think that we really understand C4 photosynthesis in all its details yet.

What are you opinions on the field of plant genetics? Is it under-represented? Is it overly commercialized?
Sorry I can’t comment on this one.

What is your opinion on patenting genomes (specifically plants)? Do you think this will happen if the IRRI succeeds in producing a C4 rice strain?

While it has to be profitable to develop improved crops, I don’t think that making the use of produced seeds by the farmers illegal is the right way to go. I would hope that the aim of the Gates Foundation is to avoid a patent on C4 rice.