A metabolic study reveals that plant-based compounds cooperate to overcome dehydration
Japanese plant biologists have exposed dynamic networks of small molecules that respond to dehydration stress in plants. Worldwide, drought is a major limitation to crop productivity, which results in economic loss and food shortages.
The researchers, led by Kazuo Shinozaki of the RIKEN Plant Science Center in Tsukuba, analyzed the so-called dehydration metabolome, which includes the complete set of small molecules, or metabolites, in drought-stressed examples of the model plant Arabidopsis thaliana. Metabolomics is a powerful tool for understanding highly complex cellular processes. Using this approach, the researchers found that particular groups of metabolites increase in abundance when water is scarce. Their results are published in The Plant Journal1.
Abscisic acid (ABA) is a phytohormone that plays a prominent role in regulating the dehydration response. Shinozaki and colleagues investigated its effect on metabolic changes in response to drought by working with a genetic mutant of Arabidopsis, nc3-2, in which ABA accumulation is significantly reduced. They found that an increased rate of accumulation of metabolites such as amino acids in response to a lack of water is dependent on ABA, and depletion of this hormone alters metabolite concentrations. In nc3-2, they observed a significantly lower increase in the levels of several amino acids, sugars and other metabolites.
In normal plants, the team found that levels of certain amino acids increased in unison during the dehydration stress response. This correlated increase in different amino acids indicates that these metabolites are part of a network, which appears to be important to the stress response. The increase in amino acid concentrations supports the idea that metabolic engineering of amino acid biosynthesis will be a promising approach for improving drought tolerance.
The rate of increase in sugars was not, however, matched to that of amino acids, demonstrating for the first time that that these two types of metabolite respond to dehydration stress through different metabolic networks (Fig. 1). Despite having lower metabolite concentrations than normal plants, ABA-deficient mutants adapted somewhat to dry conditions through moderate but synchronized increases in certain sugars and other small molecules.
The study has revealed many more ABA-dependent metabolites and metabolic pathways than previously reported. “Soon, combining mathematics, computational biology and molecular biology should provide more insight into the complex metabolic networks that constitute the response to dehydration stress,” says team-member Kaoru Urano. Understanding the sophisticated interactions between metabolites in dehydrated plants will ultimately enable better management of crops in harsh environments.
Reference
1. Urano, K., Maruyama, K., Ogata, Y., Morishita, Y., Takeda, M., Sakurai, N., Suzuki, H. Saito, K., Shibata, D., Kobayashi, M., et al. Characterization of the ABA-regulated global responses to dehydration in Arabidopsis by metabolomics. The Plant Journal 57, 1065–1078 (2009).
The corresponding author for this highlight is based at the RIKEN Gene Discovery Research Team
