Touching: No thanks

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Touching: No thanks

A path across a field of grass, noticeable because the grass is shorter. Grass we often walk over grows slower. It is one of the most eye-catching examples how plants react to repeated touch. They don’t like it. Above ground plants grow less fast, and flower later. Below ground, they anchor themselves more deeply. The response starts with recognition of repeated touch. 

Plants recognise touch and pressure using protein channels and receptors located in cell membranes. The protein channels allow a signal to pass when the cell is touched or pressed. A receptor on the other hand gives, when the cell is touched, a message to the proteins in the cell. Researchers from Sweden analysed how plants respond to light touch. For this, using a paint brush they lightly brushed the leaves. Then observed at gene level the reaction of the plant: which genes turned on and which turned off. Followed by an analysis of which proteins are essential for this reaction. Two it turned out: Feronia and CAMTA.

Feronia prevents that after a single tough growth is slowed down growth for long

Feronia is a receptor, and only gives a message when there is no touch. The message: Do not do anything, stay inactive. The receiver: the gene activators MYC2, 3, 4, and 5. In this way the plant only reacts to touch when there is touch. MYC2, 3, 4, and 5 spring into action, when there is no message from Feronia. They turn on genes needed to react to touch.

Not only Feronia, but also CAMTA is needed for the response to touch. Like MYC2, 3, 4 and 5 is CAMTA a gene activator. After a signal, most likely from a protein channel, CAMTA gets into action. It turns genes on, but a different group than those of the MYC 2, 3, 4, and 5 gene activators. The researchers noticed that activation of both gene groups is needed for the response to touch. The plant only slows down its growth if both CAMTA and MYC2, 3, 4, and 5 turn on their genes.

A touch often happens for a short moment. Quickly Feronia gives MYC2, 3, 4, and 5 the order again: Do nothing, stay inactive! Preventing slowing down the growth of a plant for long periods of time. That is, unless touching occurs time after time. Then MYC2, 3, 4, and 5 stay active and the growth slows down. By walking over the same grass over and over again, we give the message don’t grow; and a pad becomes visible.

Literature

Essam Darwish, Ritesh Ghosh, Abraham Ontiveros-Cisneros, Huy Cuong Tran, Marcus Petersson, Liesbeth De Milde, Martyna Broda, Alain Goossens, Alex Van Moerkercke, Kasim Khan, Olivier Van Aken (2022) Touch signaling and thigmomorphogenesis are regulated by complementary CAMTA3- and JA-dependent pathways. Science Advances 8, eabm2091