Researchers discover hormonal regulatory module for root elongation


Date:
September 14, 2021
Source:
Leibniz Institute of Plant Genetics and Crop Plant Research
Summary:
Plants respond to mild nitrogen deficiency by elongating their
lateral roots. In this way, more nitrogen can be absorbed than
before.

Researchers have now discovered a hormonal regulatory
module that mediates the molecular processes of this
adaptation. Brassinosteroids and auxins play a central role in this.



FULL STORY ==========================================================================
In the future, agricultural crop production will have to manage with less
and less nitrogen fertilisation. The goal must therefore be to increase nitrogen use efficiency so that yield levels can be kept stable. Plants
respond to mild nitrogen deficiency by elongating their lateral roots. In
this way, more nitrogen can be absorbed than before. Researchers at the
IPK Leibniz Institute have now discovered a hormonal regulatory module
that mediates the molecular processes of this adaptation. Brassinosteroids
and auxins play a central role in this. The results were published in
the journal Nature Communications.


==========================================================================
It is vital for plants to be able to adapt their root structure to
changes in the soil. If there is a slight lack of nitrogen, many plants elongate their lateral roots. The hormone auxin plays an important role
in root formation.

When nitrogen supply is adequate, enough auxin is transported from the
shoot to the roots for them to grow. "However, if there is a moderat lack
of nitrogen, shoot-derived auxin is not enough for adaptation, thus local biosynthesis of auxin is strongly enhanced in the root tip," explains
Prof. Dr. Nicolaus von Wire'n, head of the Department of Physiology and
Cell Biology at the IPK Leibniz Institute.

But it is not only about auxin, brassinosteroids also have an important function in this process. They are synthesised to a greater extent in the
event of mild nitrogen deficiency and are passed on as a growth-promoting signal.

"This signal in turn is necessary to induce the two genes TAA1 and
YUCCA8 in the roots," explains Dr. Zhongtao Jia, first author of the
study. "Thereby, the formation of auxin is controlled and regulated
according to the respective nitrogen demand. Ultimately, the elongation
of the lateral roots is increased in this way." "In our study, we have
thus discovered a hormonal regulatory module. What is new is that we
can arrange the hormones in hierarchical order, i.e.

brassinosteroids are upstream of auxin in this process," says Prof. Dr.

Nicolaus von Wire'n. But not only that: the IPK scientists also
found allelic variations in the YUCCA gene during their research on
the model plant Arabidopsis. "These are related to the fact that some
natural accessions (lines of certain geographical origin) show a stronger elongation of the lateral roots than others when grown under mild nitrogen deficiency." The next challenge is to use these findings for further
genetic improvement of crop plants -- for example by developing genetic
markers or by gene editing employing the CRISPR/Cas technology. "We also
expect such differences between individual lines in the barley or wheat accessions in our gene bank," says Prof. Dr. Nicolaus von Wire'n. In
addition, the IPK researchers want to investigate the questions of how
plants can measure their internal nitrogen nutritional status and which
factors might play a role in the process of root elongation even before brassinosteroids come into play.

========================================================================== Story Source: Materials provided by Leibniz_Institute_of_Plant_Genetics_and_Crop_Plant Research. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Zhongtao Jia, Ricardo F. H. Giehl, Nicolaus von Wire'n. Local auxin
biosynthesis acts downstream of brassinosteroids to trigger root
foraging for nitrogen. Nature Communications, 2021; 12 (1) DOI:
10.1038/s41467- 021-25250-x ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/09/210914152537.htm

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