Keiko Torii is piecing together how stomata control plant respiration.

Keiko Torii was drawn from an interest in cancer research to a career in plant biology, but keeps her eyes open for relevance in both areas.

When Keiko Torii gazed through the microscope at a mutant Arabidopsis thaliana leaf covered in specialized cells called meristemoids, she saw more than a beautiful anatomic anomaly—she saw a new way to probe a fundamental system in developmental biology.

Meristemoids are stem-cell-like precursors that give rise to a pair of guard cells, which form stomata—tiny pores on the skin of almost all land plants that are crucial for the exchange of water vapor and gas during photosynthesis. Close study of meristemoids has largely eluded scientists because the cells, by nature, are transient and few and far between.

“When I looked at this,” Torii says, pointing to a poster-size image of the mutant leaf with a tightly packed honeycomb of DayGlo blue meristemoids hanging on her office wall at the University of Washington, “I thought maybe this could be an economical tool to study what makes a meristemoid a meristemoid.”

To do so, she compared the readout of activated genes, known as a transcriptome, from the meristemoid-covered Arabidopsis mutant with the transcriptomes of two other mutants: one covered in only waxy pavement cells that shield plants from the elements, and one with stomata only. The study, published in the September 2011 issue of Plant Cell, revealed a novel protein that dramatically relocates during stem-cell divisions of a meristemoid.

Arabidopsis plants with the gain-of-function scrm-D mutation have an epidermis solely composed of stomata.
Image modified from Kanaoka et al. (2008) Plant Cell 20:1775-1785.

Manipulating Genes

As a biology student in Japan, Torii was set on a career in medical research. “I wanted to study cancer,” she says. But when she graduated from the University of Tsukuba in 1987, a buzz from the world of plant science turned her head. Researchers had successfully transferred specific genes from the microbe Agrobacterium into Arabidopsis thaliana, a tiny mustard plant commonly studied in labs.

“I thought, ‘Wait a minute, that’s kind of interesting. Now we can study plants by manipulating their genes in a much more sophisticated way,’” says Torii, a leafy-green cardigan draped over her shoulders.

Photo: Jose Mandojana

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