The clue is in the glue -- Nature's secret for holding it together


Date:
June 22, 2023
Source:
John Innes Centre
Summary:
An obscure aquatic plant has helped to explain how plants avoid
cracking up under the stresses and strains of growth.


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FULL STORY ==========================================================================
An obscure aquatic plant has helped to explain how plants avoid cracking
up under the stresses and strains of growth.

The finding by researchers Dr Robert Kelly-Bellow and Karen Lee in
the group of Professor Enrico Coen at the John Innes Centre, started
with a curious observation in a dwarf mutant of the carnivorous plant Utricularia gibba.

The stems of this floating plant are filled with airspaces and this
hollowness means that the vascular column inside the stem can buckle
when under stress.

This effect would not be apparent in most plants, which have solid stems.

The researchers saw that in a dwarf mutant the central column was wavy
instead of straight. They hypothesised that this wobbly spine was caused
by an internal conflict, a disparity between what was happening inside the plant stem and the epidermis or skin. Computational modelling by coauthor
Dr Richard Kennaway showed this idea could account for what was observed.

"We realized that in these types of dwarf, only the epidermis, the skin
of the stem, wants to be short, the internal tissue still wants to be
long hence the buckling effect," explains Professor Enrico Coen of the
John Innes Centre, an author of the study which appears in Science.

"This was a surprise -- previously people had thought that dwarf
varieties, which are very important in agriculture, would be dwarf
because everything in the stem is affected to grow less but in fact
it's just the skin in this case, creating a sort of straitjacket."
Further investigations revealed that the Utricularia gibba dwarf mutant
lacked a growth hormone called brassinosteroid.

They theorized that this hormone normally allows the skin to stretch,
giving a more forgiving straitjacket and allowing the plant stem to
elongate.

To test this idea, they used a mutant in the model plant Arabidopsis
that weakens the glue between cells, to see if reducing brassinosteroid
would cause major cracks to form in the skin of the stem as a result of
the stresses.

"That is exactly what we saw," explains Professor Coen. "Normally an Arabidopsis stem with weakened glue will crack slightly because the
hormone is there to loosen the straitjacket. But when the hormone was
missing, the skin was completely ripped off and the plant was almost
skinless." Computational modelling by coauthor Professor Richard Smith
showed brassinosteroid hormone was likely easing the straitjacket by
loosening fibres in the epidermal cell walls.

"Plant cells are stuck together and are forced to behave in a coordinated
way just by their pectin, their glue, that binds them. What we show in
this study is that this is an incredibly powerful force; the glue is so
strong you only need to change growth in one layer and the other cells
will follow," explains Professor Coen.

"Previous studies have emphasised that plants send molecular signals
to grow in a coordinated way, and this is still a part of the
explanation. But what our study shows is that the glueyness of plant
cells is also a vital component in coordinating growth. Sticking together
is very important." Coauthor Dr Christopher Whitewoods at the Sainsbury Laboratory, Cambridge University, emphasizes the potential importance of
these findings for future research. "The fact that mechanical interactions between cell layers control growth in the stems of two wildly different
species raises the question of whether they control other aspects of
plant development, such as the complex internal patterning of leaves. We
are excited to test whether this is the case." The findings shed light
on dwarfing varieties of crops, like wheat and rice, which underpin agriculture's Green Revolution, explaining how genes control their growth
and how we might improve their efficiency in future.

Their findings also relate to developmental processes in animals, such
as formation of crocodile skin cracks and shaping of the intestine, where mechanical interactions between layers are also thought to play a part.

Many hypotheses look promising to begin with but then fail to last the
full experimental course. Not so in this case, reflects Professor Coen.

"The first glimpse of the wobbly tissue in our dwarf aquatic plant was
exciting because as soon as we saw that, we had an idea of what might
be going on. But the biggest excitement came from testing the idea in
a completely different system.

"Nature is elusive. Ninety-nine percent of nice ideas fall flat on their
face when put to a critical test. But occasionally an idea survives
and you then know that nature has revealed one of its secrets to you,"
he says.

Brassinosteroid co-ordinates cell layer interactions in plants via cell
wall and tissue mechanics, appears in Science.

* RELATED_TOPICS
o Plants_&_Animals
# Endangered_Plants # Botany #
Biotechnology_and_Bioengineering # Genetics
o Earth_&_Climate
# Ecology # Exotic_Species # Sustainability # Rainforests
* RELATED_TERMS
o Hydroponics o Seed o Plant_defense_against_being_eaten o
Water_hyacinth o Herbivore o Fertilizer o Plant_sexuality
o Botany

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


========================================================================== Journal Reference:
1. Robert Kelly-Bellow, Karen Lee, Richard Kennaway, J. Elaine Barclay,
Annabel Whibley, Claire Bushell, Jamie Spooner, Man Yu, Paul Brett,
Baldeep Kular, Shujing Cheng, Jinfang Chu, Ting Xu, Brendan Lane,
James Fitzsimons, Yongbiao Xue, Richard S. Smith, Christopher
D. Whitewoods, Enrico Coen. Brassinosteroid coordinates cell layer
interactions in plants via cell wall and tissue mechanics. Science,
2023; 380 (6651): 1275 DOI: 10.1126/science.adf0752 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/06/230622142353.htm

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