Last night, I headed down to the lovely Bell House in Brooklyn for the monthly Secret Science Club lecture. This month's lecture was by Dr Rob Martienssen, a plant geneticist at Cold Spring Harbor Laboratory. The main topic of the talk concerned asexual reproduction in plants, and the implications it has for agriculture and the production of biofuels.
The word clone derives from the ancient Greek word for a trunk, branch, or stem- the process of vegetative propagation has long been known. Plant clones can reach gigantic proportions and extreme ages, the most massive known organism on Earth is a male quaking aspen clone known as Pando.
Although asexual reproduction typically results in genetically identical offspring, epigenetic factors can cause changes in phenotypes. A good example of epigenetic change in clonal plants is the mutation of Pinot Gris, Pinot Blanc, and Pinot Meunier grapes from Pinot Noir stock. Much of the epigenetic changes are due to the action of "jumping genes", properly known as transposons, which are segments of DNA which alter the genome of an organism.
Clonal reproduction allows hybrid plants to thrive, such hybrids often exhibit extraordinary health, or hybrid vigor- hybrid individuals with low fertility can reproduce clonally (a good example of this is Pando, the quaking aspen clone, which is believed to have not reproduced sexually for the past 10,000 years). While most clones reproduce through vegetative propagation, certain plants, notably dandelions, can produce seeds asexually.
In order to protect the integrity of the genome from the deleterious effect of transposons, small RNA molecules "silence" the jumping genes (they "clean up" the "junk" DNA). Besides gametes, pollen contains a non-reproductive "vegetative nucleus". Cells in the vegetative nucleus of plant produce the small RNA molecules which clean up the genome of a developing embryo.
Dr Martienssen ended his talk with a discussion of the potential for biofuel production using duckweed as a fuel stock. Duckweed reproduces rapidly, and can thrive in adverse conditions (low light, polluted water, varying degrees of salinity). During the Eocene epic (which was marked by extraordinarily warm temperatures- the "thermal maximum") the Arctic Ocean was largely isolated from other bodies of water, and the increase in salinity, caused dense, salty water to sink, resulting in a layer of fresh water at the surface which allowed the aquatic plant Azolla to thrive. The rapidly reproducing Azolla is thought to have removed much of the carbon dioxide from the atmosphere and the dead plants were not subject to decay in the anoxic waters near the sea bed, and were buried by sediment, sequestering the carbon.
With its prolific reproduction rate, duckweed can be incorporated into wastewater treatment systems as well as biofuel production. The use of duckweed for biofuel production is preferable to the use of traditional food crops such as corn (cars shouldn't compete with humans for fuel).
Of course, I was just about having a nerdgasm at this point, because I've long been an advocate of energy production using waste streams (Poop Power!). In the Q&A, some other audience member stepped on my dick (there's a fine line between nerdgasm and nerdrage) by asking about the use of algae rather than duckweed in fuel production. Dr Martienssen agreed that algae would be good fuel stock, but many varieties of algae require high light levels. At this time, duckweed, with its tolerance of low light levels, pollution, and varying degrees of salinity, is a better short-term candidate. The algae question being asked, I inquired about the plant immune system and its role in the grafting process. While the plant immune system is not his bailiwick, he indicated that small RNA plays a role in the ability of such grafts to thrive.
Other topics touched up in the talk were the role of Arabidopsis as the go-to lab plant in genome studies (much like Drosophila is the go-to lab animal). Dr Martienssen also touted the Weed to Wonder website as a great resource for maize genetics.
All told, this month's lecture was top-notch. Of course, I'm a big botany nerd and a big alternative energy nerd, so it was a one-two punch of pure bliss for me... accompanied by copious amounts of beer, no less.