Natural variation in the wild

Plant & zo

The science of plants and more


Natural variation in the wild

In general, researchers want to have as much control over their experiments as possible. This helps to say with certainty that the effect they see is due to the treatment they gave. The more variation during experiments, the less certain they are they can point to the cause of the effect. But sometimes more variation is needed to learn how things work in the wild.

A good example of this is the recently published research of English and Swedish researchers. They looked at how natural variation influences flowering time in tale cress (Arabidopsis). A lot is already known about how tale cress does this. In short, the product of the gene FLC stops flower development, and a period of cold is needed to completely shut down FLC production.

The shutdown of FLC occurs on the DNA. By throwing up blockades on the gene sequence of FLC, it becomes impossible to read the FLC gene. Blockades are not only on the part of the FLC gene that is coding for the protein, but also on the part of the gene that is not coding for the protein. In this study researchers looked how the non-protein coding parts of the FLC gene influence the shutdown of FLC, and thus flowering time.

In controlled lab conditions researchers could divide plants that were only different in their non-coding part of FLC in two groups. A group that turns off FLC quickly and a group that is slow in turning off FLC in response to cold (5°C). The question was, however, what is the influence of this natural variation in the wild? To find out, researchers studied tale cress (Arabidopsis) that were either quick or slow in turning off FLC, growing the plants out in the open in three different locations: in North-Sweden, South-Sweden and in Norwich in England.

When the researchers only looked when the plants start flowering after winter, they hardly saw a difference between the slow and quick FLC turning off plants. But in the warm autumn a difference was seen. Before the start of winter, the plants that were quick in turning off FLC started already making flowers.

To find out why, the researchers zoomed in on FLC, and how much it was still on. They did this at different times between germinating and the start of flowering. Thereby they found, that already by the first measurement there was variation in how much FLC was still on, this was seen on all locations. In the slightly warmer Norwich, the researchers also saw that the shutdown of FLC happens in two phases. First FLC is slowly shut down, but 50 days after germination the rate with which FLC is shut down increases. This increase in shut down rate appeared to occur when the cold activates the gene VIN3. VIN3 helps with throwing up blockades on the DNA of the FLC gen, and thus with the shutdown of FLC.

In both the slow and quick FLC turning off plants the shutdown of FLC by VIN3 occurs at the roughly the same rate. The difference between the slow and quick FLC shut down plants, researchers found, was in what they called ‘autumn expression’ of FLC. This is the total effect of how much FLC is initially turned on, and how quickly FLC is turned off in a VIN3-independent way. In a warm autumn this can result in plants, that are too quick in turning off FLC, whereby FLC is already turned off before the first cold days, and starts developing flowers in autumn.

The temperature variations from outside the lab enabled the discovery  of the effect of ‘autumn expression’. The chance of discovering this in a lab environment is small due to the standardised setting of growing plants. Sometimes you do not need more but less control to observe the effect.

Literature

Hepworth, J., Antoniou-Kourounioti, R.L., Berggren, K., Selga, C., Tudor, E.H., Yates, B., Cox, D., Collier Harris, B.R., Irwin, J.A., Howard, M., Säll, T., Holm, S., Dean, C. (2020) Natural variation in autumn expression is the major adaptive determinant distinguishing Arabidopsis FLC haplotypes. eLife 2020;9:e57671

Published by Femke de Jong

A plant scientist who wants to let people know more about the wonders of plant science. Follow me at @plantandzo

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