When studying human disease or development, scientists usually don’t start experiments directly with good old Homo sapiens, but instead begin their quest using cell lines, fruit flies, or even mice. In the plant field things are similar. And although our model organisms aren’t quite as fluffy as your standard ‘lab rat’, the come with a whole lot of benefits.
Working with plants doesn’t come with anywhere near the same kind of ethical restrictions that working with animals does. Which means that plant scientists generally have the possibility to work with their favourite, obscure, only-found-in-the-deserts-near-South-Western-Australia plant species. But we usually don’t.
Here are a couple of reasons why we choose to use model organisms, or ‘lab rats of the plant world’ instead:
- Simplicity – a good model species grows easily and quickly, produces many offspring and is ‘just right’ when it comes to size (big enough to handle, but not taking up too much space). Non-visible attributes are also important, for example, the size of its genome and its genetic ancestry.
- Keepin’ it General– Sometimes you want to ask a highly specific question, about a highly specific organism, but most of the time science aims to nudge forward our global understanding of how all plants work. While every species has its own particular idiosyncrasies, it’s probably best not to base your understanding of photosynthesis on a study of that obscure fellow who lives in underground volcanic vents. So we choose to work with something kind of ‘average’.
- Standing on the heads of giants – If you’re doing a jigsaw puzzle, it’s much easier if half of the puzzle is already done. Working on a species that other scientists have already been working on for years means there’s more information and more molecular biology tools and tricks. So hopefully, we reach the goal (more knowledge!) faster and more efficiently.
Ok, so that’s the why, but what about the who?
Meet Arabidopsis thaliana:
Clearly the King of the plant world – by far the most studied. Arabidopsis is a small eurasian weed, of nearly no commercial value. It technically can be eaten (it’s closely related to mustard and canola), but isn’t. But that’s pretty much where the bad ends!
Arabidopsis is small, and can grow under all sorts of conditions – soil, agar plates, hydroponics. It self-pollinates, and goes on to produce tens of thousands of seeds, completing its life cycle in just 6-8 weeks. On top of that, the nuclear genome of Arabidopsis was sequenced, in 2000, before any other plant, and even before those of humans and fruit flies! This genome is fairly small – 135 megabase pairs. To put that into context, the genome of wheat 17 gigabase pairs, i.e. 125 times larger! The genome structure is also quite simple, and all three genomes (nuclear, mitochondrial and plastid) have been available for years and are fairly well annotated.
If you’re not convinced, the fact that we’ve been working on Arabidopsis for over 50 years means we know the most about it compared with all other plants. And many lab techniques are developed first for Arabidopsis. You can even go online shopping for Arabidopsis mutants, spending just a couple of dollars, instead of a couple of months, to get a plant with disrupted function of your favourite gene!
By the way, there’s a bit of a debate on the common name of this one. Technically, it’s known as thale cress or mouse-eared cress. But most of us just refer to it as ‘Arabidopsis’, so that’s what we’re going with on our site.
This article is part of a series about various model plant organisms. As we post more, we’ll link them all up.