Clean slate

Plant & zo

The science of plants and more


Clean slate

Every year again, a plant makes sure it flowers under ideal circumstances. Is the plant mature, is the temperature right, are there enough nutrients, all points to consider. Including, the question, is there enough time to set seed and develop fruits after pollination. To figure out the ideal moment, a plant makes use of a checklist.

Not all points on this list can be checked simultaneously. For example, a plant can be mature, but the rest of the points have not jet been met. No worries. A plant can memorise this. By marking the genes, that by passing a point on the list, change from on to off (or the other way around) the plant makes sure a check on list does not disappear.

Research clearly documented how this is organised for the check ‘winter passed’ in the annual Arabidopsis (tale cress). If winter has not passed the gene FLC is on. FLC is turned off during the winter, when it is cold, below 10 degrees Celsius, for a long time. At the end of the winter in all the cells of the plant FLC is turned off and marked. The point ‘winter passed’ is checked.

It is convenient for a plant, that through checking of a checklist, it enables it to remember what happened without a brain. Only for the next generation it is important that all the checks on the checklist are erased again. This prevents flowering of a plant that only just sprouted. For a long time, there was a question of how the plant erased those checks.

Now a group of researchers from the UK and Austria have found out how the plant does this for FLC. This happens via a kind of a tug of war, between the gene that wants to turn FLC on, FRIGIDA, and the gene that wants to keep FLC off, FCA. FRIGIDA is needed to turn FLC on, plants without FLC can flower without a winter having passed. By shaking off the markings on FLC, FRIGIDA is turning FLC back on.

At the same time FCA tries to prevent FLC being turned on. During the reading of FLC, FCA says right at the beginning ‘here is the end of the gene’. In this way only the first part of FLC is read, but not the rest of the gene. This prevents removal of the markings on FLC, so the gene stays off.

This all happens during the first three to four days after pollination of the flower. Is there a lot more FRIGIDA, then FLC is on at the time of sprouting, then the plant needs a winter before it can flower. If there is a lot more FCA, then at the time of germination FLC is off, no winter required before flowering. Of course, it can be that the amount of FRIGIDA and FCA is somewhere between those extremes. In that case, the more FRIGIDA the longer the winter, the more FCA the shorter the winter that is needed for flowering.

It is easy to believe that all annuals and biennials use a similar system to erase the checks on their checklist. For perennials it is probably less simple. They live for multiple years and flower year after year.

Literature

Michael Schon, Catherine Baxter, Congyao Xu, Balaji Enugutti, Michael D. Nodine, Caroline Dean (2021) Antagonistic activities of cotranscriptional regulators within an early developmental window set FLC expression level. Proceedings of the National Academy of Sciences 118 e2102753118

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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