Working together

Plant & zo

The science of plants and more

Working together

The first thing a seedling does, after its germination, is growing upwards. To get above the ground into the sunlight. A seedling gets there not so much through cell division, but through stretching itself. Researchers know that this is regulated by the plant hormones auxin and brassinosteroid. But how these two growth-managers work together was up to recently not clear. But now Chinese researchers show how the two cooperate.

To investigate if the teams of those hormones really work together, the researchers observed how the brassinosteroid-team responded to instructions from auxin. They did this with help of BZR1, a gene on/off switcher which passes on instructions from brassinosteroid to the rest of the team. Under normal circumstances a seedling stretches itself after auxin application. But is BZR1 absent, then the seedling does not respond to auxin. While when there is a more than normal BZR1, the seedling goes an extra mile in its response to auxin.

In the absence of GRF4 BZR1 can go back doing its job

Subsequently the researchers studied how auxin influences BZR1. The step herein was analysing with which other proteins BZR1 interacts. The researchers noticed that BZR1 together with auxin staff member MPK3, and with the protein GRF4. GRF4 is one of those staff members that keeps you from doing your job. Just what GFR4 does by BRZ1. GRF4, observed the researchers, makes sure that the gene on/off switcher is located in the cytoplasm instead of the nucleus. Without being in the same room as the DNA, BZR1 can not do its job.

The next step was finding out what the auxin staff member MPK3 actually does. The researchers observed that when auxin is present, MPK3 transfers a marker for destruction to GFR4. In this was MPK3 removes GFR4 from BZR1. The absence of GFR4 means that BZR1 can go back to the nucleus to do its job, the turning on of genes needed so that the seedling can stretch itself. By working together, the auxin and brassinosteroid teams manage to get seedling to stick its head above the ground.


Zipeng Yu, Jinxin Ma, Mengyue Zhang, Xiaoxuan Li, Yi Sun, Mengxin Zhang, an Zhaojun Ding (2023) Auxin promotes hypocotyl elongation by enhancing BZR1 nuclear accumulation in Arabidopsis. Sci. Adv., 9 (1), eade2493.

Read more about stretching seedlings: Searching for light

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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