Agave – the cactus-like plant which forms the base ingredient of tequila – has a nocturnal ‘body clock’ which allows it to ‘breathe’ at night and withstand the driest of conditions, new research has shown.

Now scientists are hoping to harness this reverse molecular clock to engineer new drought-resistant crops that will be able to adapt to our future changing climate.

Publishing their findings in this month’s Nature Plants, the team from Newcastle University, UK, and Oak Ridge National Laboratory, Tennessee, reveal for the first time how the stomata – or ‘breathing’ pores – on the Agave’s leaves are kept shut during the day to minimise water loss.

The process is opposite to that of most plants which keep their stomata open during the day so they can take in Carbon Dioxide and use the sunlight for photosynthesis. However, this also means they lose water rapidly through evaporation.

Genes 'flipped' to reverse stomatal opening

Newcastle University’s Professor Anne Borland, one of the authors of the study, explains:

“Photosynthesis needs three key ingredients - CO₂, water and sunlight – so it follows that most plants keep their stomata open in the day when it is sunny and shut at night when it is dark.

“But for a plant living in hot, arid conditions such as the Agave, this would be disastrous. They need to conserve every drop of water they can and leaving their stomata open during the day would result in such rapid water loss they would simply die.

“What we have shown in this study is that in so-called CAM plants – Crassulacean Acid Metabolism plants like the Agave – several of the genes controlling stomatal opening have had their abundance re-scheduled or ‘flipped’ from being more abundant during the day to more abundant at night.

"Storing the carbon from the CO₂ taken up overnight, the plants photosynthesise in the day like other plants but are able to carry out the process without opening their stomata.

“If we can harness these genes and engineer new drought-resistant plants then the potential is huge in terms of developing crops and biofuels that are able to withstand the challenges we face from a changing climate.”

Crassulacean acid metabolism

CAM - Crassulacean acid metabolism - was first discovered by scientists at Newcastle University in the 1950s and is a photosynthetic adaptation found in approximately 7% of plant species.

Producing high quantities of starch and sugars in areas where water is limiting, it has long been recognised that if we can harness the properties of CAM plants they could pave the way to new biofuel crops for the production of bioethanol.

Agave is native to the hot and arid regions of Mexico and the Southwestern United States. Well-known as the base ingredient for tequila, Agave nectar is now widely marketed as an alternative to sugar.

Sequencing thousands of genes and proteins to understand the underlying metabolic processes, the team compared the Agave - or CAM - plant with Arabidopsis, a type of cress and a typical C3 plant.

They found that although both plants have the same complement of genes and proteins, over a 24 hour period certain genes were ‘switched on’ at different times.

“The plants have effectively re-programmed themselves to suit their environment,” explains Professor Borland, based in the School of Biology at Newcastle University.

“Because both plant types have a similar genetic makeup, we are hopeful that it will be possible to turn C3 plants into CAM plants simply by finding the right triggers.

“This is a really exciting discovery and a major breakthrough in our quest to create new plants that can cope in our future environment.”

The study is part of a $14m research programme funded by the Department of Energy Office of Science Genomic Science Programme. The team are currently four years into the five year project.

Reference:

Title: Transcript, protein and metabolite temporal dynamics in the CAM plant Agave

Publication: Nature Plants

Authors: Abrahams et al

DOI: 10.1038/NPLANTS.2016.178