Plants occupy > 80% of biomass on the earth, essential for our environment and food production. Plants are habitats and complete their lives in a given environment. Therefore, they have evolved unique mechanisms to adapt to environmental changes. Understanding and optimizing plant growth in changing environments is crucial for moving forward our sustainable future.
Our research interests are:
1. ABA metabolism, transport and signaling
Abscise acid (ABA) is a plant hormone that regulates growth, development and physiology. Particularly, ABA plays an important role in regulating plant water relations, such as closing stomata to decrease transpiration. ABA also regulates seed development, seed dormancy and germination.
ABA biosynthesis and catabolism are regulated by multiple developmental and environmental factors. NCED is a rate-limiting enzyme in the ABA biosynthesis that increases ABA levels, while CYP707A is a regulatory enzyme in the ABA catabolism that decreases ABA levels. Internal and external cues regulate the expression of NCED and CYP707A to balance ABA synthesis and degradation.
ABA transpoters translocate ABA across the membranes, such as plasma membranes and tonoplast membranes. The former is involved in ABA transport, while the latter is involved in ABA storage in vacuoles. ABA movement to proximal regions and long-distance movement is thought to occur via diffusion in the apoplast and vascular transport systems, such as xylem and phloem. ABA contributes to systemic abiotic stress responses in part via ABA transport.
ABA signaling and its downstream responses are tightly regulated via interaction with metabolism and transport. Molecular links between ABA metabolism and signaling form a higher-order regulation involving hormone crosstalk and other unknown mechanisms.
2. Plant environmental signaling and responses
Nitrate: Nitrate is a nutrient and also a signal molecule. It is a potent germination stimulator for many species. We found that nitrate induces the expression of CYP707A2 and decreases ABA levels in seeds (Matakiadis et al. 2009; Yan et al. 2016).
Humidity: Air humidity impacts plant growth and physiology. We found that high humidity induces the expression of CYP707A3 and decreases foliage ABA (Okamoto et al. 2009; Hussain 2024).
Plant movement: Plant parts move in response to environmental signals, such as touch, light, temperature, submergence and humidity. Some of these movements are known as avoidance response to unfavorable conditions. Plant movement replies on either asymmetric growth or reversible cell expansion. Plant hormones are actively involved in this process. We investigate the molecular mechanisms of plant movement and its impact on survival strategies (Hussain et al., 2024).
(3) Seed germination
Seed germination is a competition between the embryonic growth and inhibition by surrounding tissues, such as seed coat and endosperm. Aleurone endosperm of Arabidopsis seeds inhibit seed germination. We investigate the function of the endosperm during germination.
(4) Biotechnology
Cold Atmospheric-Pressure Plasma (CAP): Plasma agriculture comprises three elements: sterilization, fertilization and plant growth promotion. Through collaboration with Prof Okumura and Koga at Kyushu University, we investigate the effect of CAP on Canadian crops.