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AsianScientist (Oct. 2, 2017) – In a study published in Chemical Communications, scientists at Nagoya University in Japan have synthesized a bioactive small molecule that increases the number of pores, or stomata, in plants without stunting their growth.
Environmental studies have shown that 40 percent of atmospheric carbon dioxide (CO2) passes through plant stomata every year. Thus, controlling stomatal development and function is a key strategy to increase crop plant productivity and water-use efficiency. Although it is known that light and atmospheric CO2 levels influence the number of stomata, a chemical method to control stomata numbers in plants has not been identified until now.
In this study, synthetic chemists and plant biologists at the Institute of Transformative Bio-Molecules (ITbM) in Nagoya University performed a chemical screening of selected small molecules from ITbM’s chemical library and identified two molecules (CL1 and CL2) with similar structures to the non-steroidal anti-inflammatory drug, Celecoxib. Although CL1 and CL2 increased the number of stomata in plant leaves, they were toxic to the plants when applied at high concentrations.
Encouraged by the effect of CL1 and CL2 on stomata numbers, the team then modified the structure of the compounds to develop small molecules that lacked the trifluoromethyl (CF3) group in the C3-position (ZA155) or the aryl group in the C5-position (ZA099) on the pyrazole ring (a five-membered heterocycle consisting of three carbon atoms and two adjacent nitrogen atoms). The team discovered that although both compounds led to an increase in stomatal number, ZA155 led to growth inhibition of the plant, while ZA099 did not.
After further cycles of modification using methods such as palladium-catalyzed C-H arylation and anisole (methoxybenzene) substitution, the team arrived at a chemical structure that was the most effective at increasing the number of stomata without causing severe toxicity. They called this compound ZA144.
“This amazingly speedy collaboration between biologists and chemists was possible only in a research environment like our institute, where biologists and chemists work closely with one another,” said Associate Professor Naoyuki Uchida of Nagoya University.
Further investigations using their bioactive pyrazole compounds may lead to the clarification of the mechanism behind pyrazole-mediated stomatal differentiation. Such research may one day enable the identification and synthesis of compounds that can increase biomass through stomatal control.
The article can be found at: Ziadi et al. (2017) Discovery of Synthetic Small Molecules that Enhance the Number of Stomata: C–H Functionalization Chemistry for Plant Biology.
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Source: Institute of Transformative Bio-Molecules; Photo: Pexels.
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