by Sarah Wiseman
RNA extractions were my main task for the week. This involved a lot of sample grinding and centrifuging, all to collect small amounts of messenger RNA. The different messenger RNAs (or mRNAs for short) present in a cell can tell us which sections of the genome are being transcribed within it. This allows us to compare the activity of particular genes between the leaves and the roots, for example. We can also use the mRNA to search for the activity of a particular gene that we’re interested in. This is done by carrying out reverse transcription (a technique which uses RNA as a template to make DNA); we can make then sequence strands of DNA to see if different plants have copies of the same genes. My extractions were the first stage in this long process.
To stop the fragile mRNA degrading, most of the extraction process had to be done on ice or (more excitingly) liquid nitrogen! Though this does have its draw backs – wheat grains which have been frozen solid are rather difficult to grind to a powder. I spent several mornings grappling with persistently intact samples and trying to thwart their escape attempts (and not always successfully – many a grain evaded my grasp, making a bid for freedom which could only result in their binning). I even managed to destroy a motor while trying to grind down the stubborn grains!
Monday and Tuesday were spent optimising the extraction protocol, an important yet dull and quite frustrating process. For someone who didn’t understand exactly what was going on it felt a lot like alchemy – making small adjustments here, using slightly different amounts of something else there for no obvious reason. As it is there are quite a few papers in which various scientists describe their methods for RNA extraction, though deciding which of them was most suitable for our extractions was a challenge. After a period of trial and error we settled on the protocol which gave us the best quality of RNA extracted so far.
The next stage in the process is making cDNA, using the RNA just extracted as a template to create a DNA copy which can eventually be sequenced. The process itself involves more calculations and a very long wait – there is an hour’s incubation at 50oC whilst the added enzymes function.
The week ended with another induction, this one a tour of the Department’s Plant Growth Facility. The PGF is a surprisingly noisy building filled with many temperature and light controlled growth chambers, where most of the experimental plants are grown. My Arabidopsis now have their own shelf in one of the chambers and are looking rather small compared to their neighbours (which are at a much later stage of growth). Over the next few weeks I will be visiting them every few days to check on their progress, but more importantly watering them – something that it’s still best not to leave to the machines, even in 2014!