The Gilroy Lab has been again fortunate to secure NASA funding for a second experiment studying the growth of Arabidopsis plants in microgravity on the International Space Station (ISS). This experiment is called BRIC-19: Test Of Arabidopsis Space Transcriptome II (TOAST II) and GeneLAB. Similar to BRIC-17, we will use the BRIC (Biological Research In Canisters) hardware with our plants growing in petri plates inside PDFU (Petri Dish Fixation Units) as we did for BRIC-17. Our experiment will launch on September 19, 2014, tucked inside SpaceX’s Dragon capsule as part of the CRS-4 (cargo resupply mission #4). The Dragon will berth with the ISS two days later on September 21, 2014, at which point the astronauts will unpack our BRICs into the ISS and our experiment will begin.
So, what exactly will we be investigating during our second foray to the ISS?
The first half of our BRIC-19 experiment is TOAST II. Just as the lack of weight on board the International Space Station causes astronauts to lose bone mass, the weightless environment causes plants to lose their supporting structures. For the plant this means they grow long and thin in space, lacking to some degree the thickened and strengthened cell walls that they use to hold themselves up on Earth. The reason the plants are stronger on Earth is that they sense the mechanical forces generated by their own weight and lay down support materials in response to these signals. In space, the signals are gone and so the plants don’t produce the support materials. As astronaut Don Pettit (who grew the famous Space Zucchini!) put it: Plants “get lazy” in space.
Part of the machinery that lets the plant sense and respond to these mechanical forces on Earth is a group of genes called the “TOUCH” genes, so named because they are switched on in response to touch. One of these genes, named TOUCH 2, or TCH2, looks to be an important hub for a lot of information processing in the plant and so we think that the product of the TCH2 gene, i.e., the TCH2 protein, is a key regulator of the plant’s ability to sense mechanical forces such as its own weight. Dr. Janet Braam’s research group in Rice University has been able to make mutant plants with forms of TCH2 that is either always “on” or always unable to trigger touch responses. Dr. Braam very generously shared these mutants with us and so we now have plants that have this master mechanical response trigger always on or off. The plan is to compare the ‘always on’ and ‘always off ‘ to a normal plant growing in space and see if activating the touch response pathway even in the mechanically “silent” world of spaceflight can help restore growth that is more like what we normally see on Earth. We will look not only at the plants’ growth but also at their transcriptomes (the expression level of every gene in the plant) to see if the growth and gene expression of have the hallmarks of being at 1 x gravity, even in the weightlessness of space.
The other half of our BRIC-19 experiment is called GeneLAB, an exciting new program in NASA where data from experiments on the International Space Station is rapidly released to the entire research community to allow as many people as possible to study the dataset for insight into how spaceflight affects biology. The Gilroy Lab has the honor of sending the first GeneLAB experiment to the ISS!
The idea behind our GeneLAB work is that many plant biologists use the “lab rat” of plant research, Arabidopsis thaliana (also known as Mouse Ear Cress), to perform their experiments in space. This is a small, extremely well studied plant which has an enormous range of tools to help dissect its functions down to the level of genes and chemicals. Arabidopsis grows naturally in many places around the world and although Arabidopsis thaliana from Poland or China is all ‘Arabidopsis’, the plants in each area have diverged a little bit from each other and so there are varieties of Arabidopsis local to each area. These varieties are called ‘ecotypes’ and each is a little different from the next. So the question we want to answer is, do the different ecotypes used by researchers respond differently to spaceflight? If they do, which ecotype you use for your experiment might be critically important! The way to test this possibility would be to grow different ecotypes on the Space Station and compare them to the same ecotypes grown under the same conditions on Earth. Our GeneLAB experiment is to investigate this idea using three commonly used ecotypes of Arabidopsis. The ecotypes are all named after where they were found and collected, so the ones we will use are named Ws (Wassilewskija, collected in Belarus), Cvi (from the Cape Verdi Islands) and Ler (Landsberg erecta, orginally from Poland). In addition we will be using the Columbia ecotype (from Columbia Missouri, USA) in our TOAST II experiment, giving us a 4-way comparison of ecotype responses. As with TOAST II, we will look at the growth of the plants and then look at the patterns of genes that are switched on and off in each ecotype in response to growing in space.
If all goes as planned, we should get our ISS-grown BRIC-19 samples for analysis following the Dragon splashdown when the capsule returns to earth from the ISS in late October, 2014.