Why do plants flower earlier in a warming world?

Global increases in temperatures due to climate change are having detrimental consequences for plants, which tend to flower earlier than before and rush through the reproductive process, leading to less fruit and seeds. 

In a recent study published in the journal Proceedings of the National Academy of Sciences, an international team of scientists has unveiled a new mechanism that plants use to sense temperature, which could lead to solutions to counteract some of climate change’s negative impacts on plant growth, flowering, and seed production. 

Key protein involved 

The experts found that the key thermosensor of plants’ circadian clock – which determines their growth, metabolism, and when they flower – is EARLY FLOWERING 3 (ELF3), a protein playing a vital role in plant development. 

By integrating environmental cues such as light and temperature with internal developmental signals, this protein regulates the expression of flowering genes and determines when flowers grow and bloom.

The researchers investigated the molecular mechanism of how ELF3 works in vitro and in the model plant Arabidopsis thaliana. They discovered that, as the temperature rises, ELF3 undergoes a process known as “phase separation,” meaning that two liquid phases co-exist, in a similar way to oil and water.

“We believe that when it goes through phase separation, it sequesters different protein partners like transcription factors, which translates into faster growth and early flowering as a function of elevated temperature,” said senior author Chloe Zubieta, an expert in Cellular Physiology at the University of Grenoble Alpes. 

“We are trying to understand the biophysics of the prion-like domain inside ELF3, which we think is the responsible for this phase separation.”

How the research was conducted 

Since ELF3 is a flexible protein with no well-defined structure, it cannot be studied using X-ray crystallography. Instead, the researchers used a method called Small Angle X-ray Scattering and discovered that the prion-like domain forms a higher order monodisperse oligomer that is vital for phase separation. 

Similar to a ball of about 30 copies of the protein, this oligomer acts as a scaffold in order to interact with other proteins in the plant cell. When the scientists increased the temperature, the spheres came together to form a liquid phase and, later on, an ordered lamellar stack. 

Further experiments, using electron microscopy, atomic force microscopy, and X-ray powder diffraction on beamline ID23-1, confirmed these initial results.

“If we manage to tune when phase separation occurs as a function of temperature, by mutating different amino acid residues, we could ultimately delay flowering of plants under warmer conditions, allowing them to establish more biomass and make more fruits and seeds,” explained lead author Stephanie Hutin, a scientist at the French Alternative Energies and Atomic Energy Commission (CEA).

“Therefore, the next step in this research will be to add a different form of the ELF3 gene to the model plant Arabidopsis thaliana, and to see what happens when we grow them at warm temperatures. If our model is correct, we could do the same in crop species that have trouble adapting to warmer conditions,” she concluded.

More about plant flowering 

Flowering in plants refers to the process in which a plant produces flowers. This is a critical phase in the life cycle of flowering plants (angiosperms) because it’s when sexual reproduction occurs.

Flowering is controlled by a variety of environmental factors, genetic factors, and hormonal controls. 

Environmental factors

These include photoperiodism (the length of daylight), temperature, and in some cases, water availability. For example, some plants flower only after exposure to certain lengths of daylight or darkness, while others need a period of cold (vernalization) to induce flowering.

Genetic factors

The inherent genetic make-up of a plant also determines when and how it will flower. Certain genes are involved in the process of floral initiation, development, and maturation.

Hormonal controls

Phytohormones such as auxins, gibberellins, cytokinins, and ethylene are also involved in the regulation of flowering.

During the flowering process, a plant’s shoot apical meristem changes from a vegetative meristem, which produces leaves, to a floral meristem, which produces the parts of a flower. The flowers themselves are specialized reproductive structures that include sepals, petals, stamens (male organs), and carpels (female organs).

The main goal of flowering is to enable reproduction. This can occur through self-pollination, where the pollen from the stamen fertilizes the ovules in the carpel of the same flower, or cross-pollination, where pollen is transferred from the stamen of one flower to the carpel of another flower, often by wind or animals. 

After fertilization, the ovules develop into seeds and the surrounding ovary ripens into a fruit. The seeds can then be dispersed to give rise to new plants.

Flowering is a complex process that scientists are still studying to understand fully. Researchers use model organisms like the thale cress (Arabidopsis thaliana) to investigate the molecular biology underlying flowering.

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By Andrei Ionescu, Earth.com Staff Writer

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