ARCHIVED - A Powerful New Tool for Plant Research

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February 07, 2007— Ottawa, Ontario

Genomics and proteomics have revolutionized the life sciences by giving researchers systematic tools for identifying and deciphering the DNA and proteins found in living organisms. Now, a team at NRC is offering plant biologists around the world a powerful new tool for understanding how plants function, hormone profiling – a detailed profile of the signaling molecules, or plant hormones, which regulate their growth and development. The insights from these profiles offer many benefits for Canada – from new crops that are more drought-tolerant or have higher yields to mass-produced seedlings for reforestation.

Plant hormones are small molecules that include auxins, cytokinins, abscisic acid, gibberellins, jasmonic acid, brassinosteroids and ethylene. "They control how roots grow, how plants cope with environmental stresses, how seeds germinate – even how plants bend towards light – by turning genes on and off," says Dr. Suzanne Abrams, Principal Research Officer at the NRC Plant Biotechnology Institute (NRC-PBI) in Saskatoon.

Dr. Suzanne Abrams, Principal Research Officer at the NRC Plant Biotechnology Institute (NRC-PBI)
Dr. Suzanne Abrams, Principal Research Officer at the NRC Plant Biotechnology Institute (NRC-PBI)

For example, abscisic acid (ABA) – a family of hormones that Dr. Abrams has studied for over two decades – is responsible for closing plant stomates (leaf pores) during drought conditions. ABA also inhibits seed germination while the gibberellins promote it. "We can use plant hormone profiling to study any research problem that has a hormonal dimension such as drought tolerance in corn, ripening in fruit, and seed development and dormancy," she says.

About five years ago, with funding support from NRC and university partnerships, Dr. Abrams, Dr. Andrew Ross and their colleagues started to develop a multiple hormone profiling technique. "We knew how to analyse tissue samples for ABA-type hormones, and thought that if other researchers are focusing on genomics and proteomics, we should expand beyond ABA and related compounds to other hormone families," she says. "We felt we could give an overview of all the hormone levels at the same time and in the same tissues that other researchers were using to study the genes and proteins."

"Since the same hormones are found in every plant, it's worth developing a universal method," stresses Dr. Abrams. "The biggest challenge, however, was that plant hormones are present in very low levels within tissues that contain thousands of other chemical compounds, such as sugars, starches, oils, salts and secondary metabolites. Another challenge was to find a way to measure hormones that have a wide range of chemical properties – including acids, bases, polar and neutral compounds – in the same experiment, with minimal disruption to them."

Building on NRC-PBI research and the methods of other scientists, who have developed protocols for extracting and measuring individual hormones, plant tissues are spiked with known amounts of isotope-labeled hormones and an extraction method that works on everything is used – although some tweaking is often required when a new plant tissue is tried for the first time.

The NRC-PBI team then uses high performance liquid chromatography (HPLC) to separate the plant compounds. The HPLC is connected to two mass spectrometers running back-to-back, which measure the concentrations of different plant hormones, relative to the added standards. The detectors of the mass spectrometers are set to make other plant compounds invisible.

Dr. Abrams says it takes about a week to complete the laboratory work for a hormone profile, of which the HPLC-mass spectrometry phase requires only one hour. "We can analyze about 20 hormones at a time, including most of the known hormones in the ABA family. However, we're only analyzing four out of about 150 known gibberellins, and we haven't yet started tackling a steroid hormone called brassinolide that is present in thousand-fold lower levels than other hormones," she says.

While many researchers around the world are measuring plant hormones, the NRC-PBI team is virtually alone in terms of its comprehensive approach to hormone profiling. Hormones are among the toughest molecules to analyze because they are so transient.

The NRC-PBI team of ten scientists and technicians currently analyzes several thousand tissue samples a year, for clients ranging from Canadian universities to British and American research institutes and multinational corporations one of which has developed a drought-tolerant corn by altering a hormone pathway. The NRC team's role is to show whether the hormone levels reflect the actual field results they're seeing.

In other projects, the NRC team is working with a University of Victoria team led by Professor Patrick von Aderkas, who is developing new ways to produce pine seeds quickly for the B.C. Ministry of Forests, in order to reforest areas devastated by the pine beetle. The idea is to convince a young tree that it is mature enough to produce flowers and cones, by stimulating a hormonal pathway.

The team is also using hormone profiling in NRC-PBI genomics research on canola oil seeds. "This can tell us which hormones are involved in oil deposition, seed maturation, desiccation tolerance, and other plant processes," she says. "Understanding the hormone, gene expression and protein status of canola seeds will lead to the development of canola with more oil and improved quality."

In partnership with researchers at the University of Saskatchewan and Simon Fraser University, Drs. Abrams and Ross are seeking funding to establish a "Canadian Centre for Plant Hormone Profiling." If the application is successful, the NRC/University of Saskatchewan-based Centre will help make hormone profiling affordable for university researchers working on limited budgets. The Centre will also hold workshops to train students in hormone research and support networks of biologists interested in plant metabolism, plant stress responses and seed biology.

"We're developing a high-level technology platform and service for Canadian scientists," states Dr. Abrams, "that promises to advance the progress of Canadian plant research and ultimately benefit our farmers and the forestry industry."

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