Why is Cancer Not a Big Deal for Plants?
Plants can get cancer. Do you know the key difference between plants and animals that makes cancer mildly complicated for plants, but very serious for us animals?
Our cells can move!
Movement is one of the 5 basic principles of development: processes that enable a single cell to develop into a fully-functioning grown-up organism. Take a moment to realize how neat this is: first, that a single cell develops into a living creature. Second, everything that cells do in this process falls somewhere within these 5 developmental principles:
1. Cells can make more cells (Proliferation)
Cue images from your classic biology textbook: mitosis and meiosis. Cells need to make more cells in order to grow. I suppose the alternative would be giant single-celled organisms limited by the vulnerability of membranes containing that much cytoplasm and organelles with enough mitochondria to keep the whole thing running… Physics likely have something to say about that. Luckily we are made of more than one cell.
2. Cells can interact with other cells (Cell Signaling)
How does a cell know it is in the heart instead of a pinky toe? Having this confused can lead to problems. But cells communicating with the cells around them enable them to “know” where they are and turn on the right genes, which brings me to:
3. Cells can turn on different genes (aka Differential Gene Expression)
Muscle cells and neurons look pretty different and do different things (luckily). In the past this baffled scientists as they wondered whether different-looking cells had different genomes (total DNA) or if they all had the same DNA, but used different parts of it. Now we know differential gene expression, or using different parts of the genome in different cells, or in different parts of the cell is how cells can be different from one another.
4. Cells can move or stretch (Movement and Expansion)
Cancer is dangerous in animals because cells with uncontrolled proliferation (see principle 1) can spread to other parts of the body, whereas plant cells with cancer are stuck wherever they are in the plant body. The difference? Cell walls hold plant cells in place up against one another. Instead of being able to form essential tissue layers like animals do with cells moving between each other, plant cells divide and elongate. This is also how plants can grow towards the light, with cells on one side growing longer than the other.
5. Cells can die on purpose (Apoptosis)
This is why we do not have webbed feet. Cells have a function called “programmed cell death”, which enables plants to form deserts of dead cells around fungal pathogen infections—think dead spots on leaves—and enables tissues that are important for development to disappear in the mature adult.
As these 5 principles of development interact, an incredible display of teamwork, coordination, and mystery allow one cell to develop into an organism, with everything it needs to go about life doing its cat, human, plant, or fungi thing as a grown organism.
-Adrienne L. Godschalx
*This blog is part of my Principles of Biology series as a Teaching Assistant in lecture (Portland State University, Winter Term 2016, Bi 212, taught by Dr. Daniel Ballhorn). Many students have asked me for study or note-taking strategies, and I always point them towards finding the overarching patterns and guiding principles before memorizing the details. So I decided to walk the walk and highlight overarching patterns that I never fully grasped before or that continue to astound me. Reading my creative assimilation of certain principles of biology does not replace studying, attending lecture, or reading the textbook.