Dampening the effects of nighttime chills
Plants respond strongly to cold during the day. While night time chilling only gets a mild response. Now researchers from the University of Galsgow show in the New Phytologist how alternative splicing of REVEILLE2 dampens the effect of nighttime chill.
The circadian clock regulates many aspects of a plant development. Including its response to cold. The clock genes CCA1 and LHY are central to this. They are part of the family of DNA-binding MYB-domain containing genes. With the MYB-domain crucial for their function. Like activating CBFs, cold responsive genes, upon sensing cold during the day. But what happens at dusk was so far unknown.
The researchers decided to find out. For this they used transcript-specific RNA-seq analysis to not only identify which genes change their expression when the nighttime chill comes. But to also find out how different splice variants change in response to cold. There can be variation in the part of a gene that is used by the translation of a gen into a protein. The resulting variants are called the splice variants that gene. Using this technique they found that after just 20 minutes two genes were differently alternative spliced. One showed only a low expression, but the other was highly expressed. Which sparked the interest of the researchers. This gene was RVE2, of REVEILLE2.
RVE2 is telling the rest of the plant: relax, this chill is over soon
RVE2 is part of the same family as CCA1 and LHY. And what the researchers observed was that in warm temperatures the preferred RVE2 splice variant was short without the MYB-domain. But as soon as the temperature dropped, another splice variant appeared, one with the MYB-domain.
Subsequently the researchers studied the influence of the MYB-domain containing splice variant. Hereby using a plant that could not produce the MYB-domain containing splice variant. With help of a circadian reporter gene they revealed that when it is warm these plants were half an hour out of sink with normal plants. This increased to up to an hour in the cold. Linking nighttime chill response to the circadian clock. In addition the researchers found that in contrast to CCA1 and LHY, RVE2 is not activating, but dampening CBFs expression.
It looks as if RVE2 is telling the rest of the plant: relax, this chill is only temporary, soon it will be light and warm again. This study shows how RVE2 integrates normal nighttime cooling into its system. Laying the foundation for further research into how the plant integrates normal seasonal temperature fluctuations into its routine.
Literature
James, A.B., Sharples, C., Laird, J., Armstrong, E.M., Guo, W., Tzioutziou, N., Zhang, R., Brown, J.W.S., Nimmo, H.G. and Jones, M.A. (2023), REVEILLE2 thermosensitive splicing: a molecular basis for the integration of nocturnal temperature information by the Arabidopsis circadian clock. New Phytol. https://doi.org/10.1111/nph.19339
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