GABA is best known as a neurotransmitter helping animals to walk, talk, think and breath. However, GABA is also known in the plant world as a key carbon:nitrogen metabolite that increases in concentration massively in plant tissues in response to stress – so when plants encounter drought, salinity, acid soils, anoxia, pathogens or extreme temperatures. Also GABA can affect plant growth or guide pollen tubes through female tissue affecting fertilisation and seed set.
This has led to much speculation over the last 15 years or so that GABA might be a signal in plants. However, as no similar proteins to GABA receptors in animals exist in plants there was no proof.
Our work out today in Nature Communications shows that GABA can indeed be a signal in plants. Interestingly, it can also affect electrical signals in plants – so is similar to its mode of action in animals – but it acts through very different proteins.
The proteins that transduce GABA signals in plants are anion channels so have a similar functional property to GABA receptors in animals, however, they are very different looking proteins that share little similarity in structure.
Interestingly, these proteins are widespread in plants and are already known to have key physiological roles. The fact that GABA can modify their activity means that we have come closer to understanding how plants interpret their environment i.e. how plants transduce environmental signals into changes in growth.
By identifying this novel signalling pathway in plants we believe we have opened up the doors to a new research areas that could be exploited to improve plant responses to stress.
See press release here for more info.
Ramesh et al. show that the mammalian neurotransmitter GABA is an endogenous signalling molecule in plants. Activity of plant-specific anion channels is gated by GABA leading to multiple physiological effects including the regulation of pollen tube and root growth (pictured). Compiled z-stack of four-day-old GABA responsive wheat root tip and apical region with cell walls stained with propidum iodide captured using Nikon A1R confocal excitation 561 nm, emission 595-650 nm; captured by Stefanie Wege. (inset, bottom) Response of wheat ALMT1 protein to malate, GABA and bicuculline and GABA molecule (top)