Research

Our research is focused on molecular mechanisms of stomatal reactions and N-acylethanolamine (NAE) signaling in plants.

Stomatal signaling

Life on earth largely relies on photosynthesis – a process where atmospheric CO2 is converted to carbohydrates by plants. A key question for plants is how to facilitate sufficient CO2 uptake while preventing excessive loss of water. This is controlled by stomata, microscopic pores in the epidermis of plant leaves surrounded by a pair of guard cells. Stomata also restrict the entry of ozone – the major air pollutant with increasingly negative impact on crop yields, global carbon fixation, and climate change.

We study plant stomatal regulation in response to airborne signals such as ozone, but also CO2 and humidity. For that we use model plant Arabidopsis thaliana and custom made gas-exchange system which enables monitoring plant stomatal responses in intact plants.
In collaboration with Plant Stress Group we have recently identified SLAC1 (SLow Anion Channel1 associated) protein and showed that it is essential for stomatal closure in response to ozone, CO2, humidity and light, but also ABA, NO and Ca2+. SLAC1 encodes an essential subunit of guard cell plasma membrane S-type anion channel function or regulation. Part of our current work is related with further functional characterization of SLAC1 protein.
Earlier work has shown that several regulatory proteins such as kinases and phosphatases are involved in the regulation of guard cell anion channels. Therefore we now utilize different strategies to identify upstream signaling of SLAC1 protein.

Another topic of our research is ozone induced stomatal closure. We have shown that ozone induces rapid but transient stomatal closure starting almost immediately after the onset of ozone. This process is regulated by ABI1 and ABI2 phosphatases, OST1/SRK2E kinase and SLAC1. Our interest is to understand how this process is regulated and what its biological importance for plants is. We have also started the genetic screen for identification of novel Arabidopsis stomatal regulation mutants.

In collaboration with Plant Stress Group led by Jaakko Kangasjärvi we have recently identified SLAC1 (SLow Anion Channel1 associated) protein and showed that it is essential for stomatal closure in response to most known stimuli involved in stomatal regulation. SLAC1 encodes an essential subunit for guard cell plasma membrane S-type anion channel function or regulation.

NAE signaling

N-acylethanolamines (NAEs) are a group of fatty acid amides that are composed of a fatty acid and an ethanolamine. NAE 20:4, with 20 carbons and 4 double bonds in its fatty acid moiety, also known as anandamine, has been intensively studied in animal research due to its involvement in the endocanabinoid signaling. Several other NAEs, in addition to NAE 20:4, have also been found to modulate a wide range of physiological and behavioral processes in mammals.

Recently, NAEs have been identified in several plant species, and their levels varied in response to environmental and developmental cues. Exogenously applied NAEs (NAE 12:0 and 18:2) inhibited Arabidopsis seedling growth. In addition, exogenous NAE 12:0 and ABA had a synergistic inhibitory effect on seedling growth. Arabidopsis overexpressing a fatty acid amide hydrolase (FAAH), an enzyme that metabolizes NAEs, had a lower NAE content and could overcome the growth inhibitory effects of exogenous NAEs. Surprisingly, the AtFAAH-overexpressing plants were hypersensitive to exogenous ABA. An AtFAAH-GFP construct, when expressed in Arabidopsis, conferred NAE tolerance in transgenic plants. However, the AtFAAH-GFP-expressing plants also showed slightly higher resistance to ABA than wild-type plants.

We propose that NAE and ABA signalings interact, at least in part, via FAAH-mediated protein-protein interactions. We are currently applying molecular genetics approaches, such as split-ubiquitin membrane yeast two-hybrid and reverse genetic screens, to identify potential components involved in the crosstalk between NAE and ABA signalings.