A brake on stomata
Plant adapt their growth to their environment. A leaf, for example, growing under higher CO2 concentrations has fewer stomata. Swedish researchers show in Plant, Cell & Environment how plants are regulating this.
The researchers started their research with the question how the environment influenced leaf growth. Using a plant without CDK8, a protein that regulates gene activators. Plants without CDK8 are tiny. They appeared as shown by measurements to use water less efficiently. A trait that got the researchers looking at the stomata of the CDK8 less plants.
A plant is in a way breading CO2 in and water out through their stomata, pores, that are located at the bottom of the leaf. A plant can regulate their ‘breathing’ by opening their stomata for longer or shorter times. But this appeared not to be different between plants with and without CDK8.
CDK8 limits the amount of stomata that develop
Subsequently the researchers analysed the number of stomata in plants without CDK8. This turned out to be a relatively higher amount than in plants with CDK8. Explaining the water loss. To find out how CDK8 influences the number of stomata, the researchers looked at the genes that were turned on and off in plants with and without CDK8.
Zooming in on the genes that have a function in stomata development, the researchers found the gen regulator SPEACHLESS, and the genes that SPEACHLESS regulates. SPEACHLESS regulates the development of leaf cells in stomata. When SPEACHLESS is present the cell will develop into a meristemoid mother cell, which in turn divides asymmetrically. Her smallest daughter cell, also called the meristemoid cell, is dividing symmetrically one more time. Her daughter cells form together the two halves of a stomata.
The question was if CDK8 influences SPEACHLESS directly. To find out the researchers analysed if these two proteins could bind to each other. Which, it turned out, they could. But not only that. CDK8 is also labelling SPEACHLESS for degragdation.
In this way CDK8 keeps the amount of SPEACHLESS in control. In doing so putting a brake on the number of stomata. Without CDK8, the break is taken of SPEACHLESS, increasing the number of stomata as a result.
Literature
Hermida-Carrera, C., Vergara, A., Cervela-Cardona, L., Jin, X., Björklund, S. & Strand, Å. (2024) CDK8 of the mediator kinase module connects leaf development to the establishment of correct stomata patterning by regulating the levels of the transcription factor SPEECHLESS (SPCH). Plant, Cell & Environment, 1–15. https://doi.org/10.1111/pce.15102
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