Old leaves first

Plant & zo

The science of plants and more


Old leaves first

Sometimes it rains a lot, or there is a flooding, and before you know it a plant is submerged. Not the end of the world, as long as it doesn’t last long. But when it does, then one by one the leaves of the plant will die. Starting with the oldest. Dutch researchers figured out how a plant organises this.

Flooding manager ethylene makes sure the reaction to flooding happens as it should be. Under normal circumstances ethylene flies away. Except when the plant is submerged, then it can’t get away, and it must do its job: The turning on gene-on switches, like EIN3. EIN3 in its turn makes sure that the correct action to flooding is initiated. One of which is to initiate the death of the older leaves so the plant can use the energy stored in those.

The researchers analysed how the plant manages to sacrifice its older leaves first. Plants that did not have any EIN3 did not had a preference to sacrifice its older leaves first. But the normal preference to sacrifice its older leaves first, it turned out, was not due to the amount of EIN3 in the leaves. The amount of EIN3 increased due to flooding in both young and old leaves.


ORE is only activated in old leaves


EIN3 is not by itself making the distinction between old and young leaves. But one of the genes that EIN£ is turning on, the initiator of leaf death, ORE1, is. Plants without any ORE1 did not have a preference for which leaf dies first. Just as for EIN3, ORE1 also increased in both young and old leaves after submergence. But only in old leaves ORE1 was also activated after submergence. ORE1 could only do its job in old leaves.

Using a plant that makes more ORE1, the researchers studied how ORE1 was activated. Placing these plants in a dark room filled with ethylene the researchers observed ORE1 being turned on. But only when ethylene was present.

Flooding manager ethylene is regulating both the production as activation of the leaf death regulator ORE1. This activation happens quicker in old than in young leaves. But how ethylene is activating OER1, and what is causing that this occurs quicker in old leaves, is something the researchers have not discovered yet.

Literature

Tom Rankenberg, Hans van Veen, Mastoureh Sedaghatmehr, Che-Yang Liao, Muthanna Biddanda Devaiah, Salma Balazadeh, Rashmi Sasidharan (2022) Ethylene-mediated phosphorylation of ORESARA1 induces sequential leaf death during flooding in Arabidopsis. bioRxiv 2022.11.23.517613; doi: https://doi.org/10.1101/2022.11.23.517613  

Published by Femke de Jong

A plant scientist who wants to let people know more about the wonders of plant science. Follow me at @plantandzo

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