From growth to flowering

During the transition from growth to flowering the growth centre is changing from form and function. Instead of leaves, it now will produce flowers. The team of George Coupland characterised what exactly changes and how the plant is regulating this.

Growth centres are the reason that plants can grow new tissues during their whole life. For example the root growth centre produces new roots. And the shoot growth centre produces new shoots and leaves. But when it is time to flower and reproduce, the shoot growth centre undergoes a transformation. No longer will it be repressing flower development genes. Now the growth centre will start repressing shoot and leaf genes. But what is happening during this transition, that the researchers decided to find out.

To start they characterised the visible changes that occur during the transition of the growth centre. They discovered that the growth centre is not only increases in size, it also gets dome shaped. An important regulator in all this appeared to be AP2. Growth centres of plants without AP2 did not show those changes. But when plants produced more AP2, then the growth centre was increasing even more in size.

During the transition from growth to flowering SOC1 takes over from AP2

The growth of the growth centre, so discovered the researchers, occurred manly due to the fact that the zones directly outside the centre increased in size. There were more daughter cells that were ready for further development. During the first four days of the transition they were still developing leaves. But after that they also started to develop flowers, and seven days after the start of the transition they only developed flowers.

Subsequently the researchers studied how long the AP2 stays. Because it is known from AP2 that it is repressing flowering. But, so discovered the researchers, AP2 is absent seven days after the start of the transition. This was due to the flower development promoting SOC1. SOC1 appears at the start of the transition, However, in the beginning AP2 tries to prevent SOC1 being there. This works for about seven days after the start of the transition. After that SOC1 takes over and holds back AP2.

The moment that SOC1 takes over for AP2, the transition is complete. Then the growth centre can only produce flowers.

Literature

Bertran Garcia de Olalla, E., Cerise, M., Rodríguez-Maroto, G. et al. Coordination of shoot apical meristem shape and identity by APETALA2 during floral transition in Arabidopsis. Nat Commun 15, 6930 (2024). https://doi.org/10.1038/s41467-024-51341-6

From growth to flowering