Receiver discovered

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Receiver discovered

Plants use volatile compounds for communication. Lots is known about how these compounds are made and distributed. But how plants recognise these volatile compounds remained a mystery for a long time. Now American researchers have discovered one of these volatile receivers.

That the receivers of volatile compounds in plants remained for a long time unknown is because mostly there are no perceived differences in absence of these receivers.  This changed when the researchers discovered that the stigma of petunia flowers remains small in absence of specific volatile compounds.

Normally the flower will produce the stigma growing volatiles themselves. But not when the gene needed for producing these volatiles is absent. In these plants the stigma stays small. But when the researches exposed the developing stigma to flower produced volatile compounds, then the stigma grows to its normal size. With this the researchers discovered a perceived difference.

Using this the researchers analysed the gene regulation in order to discover the receiver of the needed volatile compound. They noticed that genes involved in the regulation of the volatile compound karrikin, a substance that is produced in forest fires, were differently regulated.

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Plants have receptors to perceive specific volatile compounts

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It is known that plants recognise karrikin with the KAI receptor. With this in mind the researchers looked at which of the four KAI receptors were switched on in the petunia stigma’s. This, it turned out, was KAI2ia. The researchers developed KAI2ia missing plants in order to be sure that KAI2ia was indeed the receiver of the needed volatile compounds. Also in these plant the stigma stayed small, also after exposure to the needed volatile compounds.

After having discovered the receiver, the researchers could now discover which specific volatile compound was it perceived. First they grew the stigma in presence of specific volatile compounds. They noticed that only after exposure of (−) – germacrene D the stigma grew to its normal size. This was also the case for the stigma of the plants that did not produce the volatile compounds, but not for the stigma’s of the KAI2ia missing plants.

Next the researchers went on to discover what KAI2ia does after recognizing (−) – germacrene D. For this they studied which proteins KAI2ia bind. This turned out to be MAX2. Together, they make sure that the gen-off switch SMAX1 is broken down. Which in turn allows the switching on of the stigma growing genes.

The researchers show that the recognition of specific volatile compounds result in regulating specific genes. Now the challenge will be to discover the other receivers for all the other volatile compounds that plants use to communicate.

Literature  

Shannon A. Stirling et al., Volatile communication in plants relies on a KAI2-mediated signaling pathway.Science383,1318-1325(2024). www.science.org/doi/10.1126/science.adl4685

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