TORward the light: The Energy Switch In Flowering Time Control
Dr Vanessa Wahl, a Research Group Leader in the Department of Cell and Molecular Sciences at The James Hutton Institute, worked collaboratively in a study led by Dr Camila Caldana at the Max Planck Institute of Molecular Plant Physiology in Germany, that has identified a new mechanism by which plants link resource availability to flowering at the correct time, maximising their chances of reproductive success.
The study found that this occurs via interaction between a well-established component of energy management, the target of rapamycin (TOR) complex, and the protein RAPTOR1B.
TOR is a master regulator of growth and nutrient sensing, conserved not just in plants, but also in animals, including humans.
Previous research has revealed that several molecular pathways, connected through an extensive network, control flowering time, taking internal and external cues. Complex interactions between light perception, sugar signalling, circadian rhythms (the internal clock present in all organisms), plant hormones and temperature sensing, allow plants to adapt to seasonal change and therefore to flower at the optimal time. This new study provides a detailed understanding of how TOR integrates into this complex network.
The exposure to cycles of light and dark is conveyed to the flowering network through what is known as the photoperiod pathway and changes according to the season and latitude. The photoperiod pathway allows plants to accelerate flowering as daylength increases in the spring to co-ordinate with the emergence of pollinators and the arrival of more favourable growing conditions.
This research found that the TOR complex not only sits at the centre of a plant’s energy management, but also directly connects energy sensing with the photoperiod pathway of the flowering network.
“While we understand the role of light and circadian signals, far less is known about signals reporting of nutrient availability.”
Dr Vanessa Wahl, The James Hutton Institute
The correct flowering time for annual plants is critical for their reproductive success and is a key determinant for crop yield.
Dr Wahl’s research delves into the mechanisms by which plants can observe how much energy they have left. She said, “While we understand the role of light and circadian signals, far less is known about signals reporting of nutrient availability.”
Dr Caldana said, “By studying Arabidopsis, a small flowering plant related to cabbage and mustard, we found it is RAPTOR1B which connects the signalling network that regulates cell growth in response to nutrients, growth factors and cellular energy with post-transcriptional regulation of a plant’s physiological reaction to the length of daylight.
“Understanding how environmental factors influence a physiological process, as mediated by TOR, can have a huge impact on fine-tuning reproductive success and consequently crop productivity. Elucidation of this new pathway provides opportunities to optimise the process in different environments by selecting genotypes with a modified TOR pathway. These findings provide an opportunity to improve crop resilience and yield in the face of environmental change.”
Agriculture and food systems are experiencing significant challenges related to climate change, including impacts on land availability, crop yields and food nutritional properties. Simultaneously, there is a need to achieve food security for a burgeoning world population alongside transitioning towards more climate-resilient and sustainable farming requiring the implementation of less damaging management systems.
Understanding the plant’s ability to coordinate growth and development with environmental signals including nutrient availability, will make a vital contribution towards food security and the sustainable management of our natural resources both in the UK and internationally.
These findings can now be translated to crop species to enhance future production and create more resilient food systems, ultimately shaping the future of sustainable agriculture and global food security.
More information is available here: https://www.pnas.org/doi/10.1073/pnas.2405536122
