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Keiko Torii on the MUTE gene and stomatal development

Tuesday, May 8, 2018 - 09:45

Stomata are tiny, microscopic, and critical for photosynthesis - a process plants use to convert sunlight and carbon dioxide to oxygen. Understanding how stomata form is critical to understanding how plants grow and produce the biomass upon which we thrive.

In a paper published May 7 in the journal Developmental Cell, a University of Washington-led team describes the delicate cellular symphony that produces tiny, functional stomata. The scientists discovered that a gene in plants known as MUTE orchestrates stomatal development. MUTE directs the activity of other genes that tell cells when to divide and not to divide.

“The MUTE gene acts as a master regulator of stomatal development,” said senior author Keiko Torii, a UW professor of biology and investigator at the Howard Hughes Medical Institute. “MUTE exerts precision control over the proper formation of stomata by initiating a single round of cell division — just one — in the precursor cell that stomata develop from.”

Torii’s team showed that one of the genes activated by the MUTE protein to its DNA is CYCD5;1, a gene that causes the GMC to divide. The researchers also found that MUTE proteins turn on two genes called FAMA and FOUR LIPS. This was an important discovery because, while CYCD5;1 turns on cell division of the GMC, FAMA and FOUR LIPS turn off — or repress — the cell division program.

“Our experiments showed that MUTE was turning on both activators of cell division and repressors of cell division, which seemed counterintuitive — why would it do both?” said Torii. “That made us very interested in understanding the temporal regulation of these genes in the GMC and the stomata.”

Through precise experiments, they gathered data on the timing MUTE activation of these cell division activators and repressors. They incorporated this information into a mathematical model, which simulated how MUTE acts to both activate and repress cell division in the GMC. First, MUTE turns on the activator CYCD5;1 — which triggers one round of cell division. Then, FAMA and FOUR LIPS act to prevent further cell division, yielding one functional stomata consisting of two guard cells.

“Like a conductor at the podium, MUTE appears to signal its target genes — each of which has specific, and even opposite, parts to play in the ensuing piece,” said Torii. “The result is a tightly coupled sequence of activation and repression that gives rise to one of the most ancient structures on land plants.”

Read the full story in UW Today.

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