Seeds can change their coats for the season

Whenever I teach on seeds, either in my non-majors Food class or my Plant Physiology class for majors, I can’t help describing them as the children of the mother plant. I know, not exactly creative, but it helps to paint a picture of the roles of the parent plant and the seed. I like to talk about how the endosperm or other food reserve is like a packed lunch, put there by the caring mother to feed the baby plant as it germinates and becomes able to feed itself. And what kind of parent sends its babies out without a coat? It usually gets a few chuckles, at least, to put this all in human terms.

That coat on the seed? Sometimes it’s a jacket, and other times it’s more like a down coat, and the mother plant chooses based on the temperature. I’m not making this up. In a study published this week, plant scientists link the toughness/thickness of the seed coat to the temperature endured by the mother plant. If the mother experienced warmer temperatures, it will make more of a protein that limits the production of tannins in the fruit. Less tannin makes for a thinner seed coat and faster germination. On the other hand lower temperatures cause the mother plant to make more tannins, leading to a thicker coat. Simple, yet remarkable.

See a news article on this research, or go check out the paper itself.

A gene that helps roots find water

I’ve been reading on plant water sensing to get some better background for projects we’re starting in the lab this summer. I came across the photo below in a paper describing the identification of a gene involved in sensing water gradients, called miz1, short for MIZU-KUSSEI1, the words for “water” and “tropism” in Japanese.

miz1 mutant roots failing to respond to water gradientThe photo shows an elegant experiment the researchers designed to pick out mutants in water sensing. They allowed the roots to grow in a Petri dish along a block of agar (seen in the upper left part of each panel) and into an opening. Normally, an open space in a closed Petri dish would have very high humidity, but they added a solution that soaks up water vapor, so the air was very dry.

The two photos across the top (D1 and D2) show the response of a wild-type root when it grows into the dry chamber — it immediately turns back toward the agar surface, where the water is. The two photos across the bottom (E1 and E2) show the mutant failing to curve back toward the agar. They found this mutant like a needle in a haystack, by looking at 20,000 mutant lines for ones like this, that fail to respond to the water vapor gradient.

The researchers have gone on to study this gene in great detail, and have made a number of exciting discoveries about how plants sense water.

Citation: Kobayashi, A., A. Takahashi, Y. Kakimoto, Y. Miyazawa, N. Fujii, A. Higashitani, and H. Takahashi. 2007. A gene essential for hydrotropism in roots. Proceedings of the National Academy of Sciences of the United States of America 104: 4724–4729.

Finding the algorithm: An introduction to reading and understanding scientific papers

I love this concise primer on how to take apart a scientific paper, and it translates almost perfectly to the literature I commonly assign in my upper-level undergraduate classes as well.

JBC [Journal of Biological Chemistry] papers, as is with articles in most biomedical journals, have a basic structure/algorithm.  Once you’ve mastered the algorithm, presenting the paper is much easier.