permaculture

[Lawrence London <lfljvenaura@gmail.com>]

https://phys.org/news/2017-04-team-genetic-hardier-stress.html#nRlv
Team identifies genetic target for growing hardier plants under stress
April 24, 2017 by Katherine Unger Baillie
Research by a Penn-led team identified a key protein involved in how plants
develop root hair cells, which take up water and nutrients. Here, a
confocal image shows a plant’s root hair cells (outlined in black) along
with folded RNA …more
<https://phys.org/news/2017-04-team-genetic-hardier-stress.html#nRlv>

The function of a plant's roots go well beyond simply serving as an anchor
in the ground. The roots act as the plant's mouth, absorbing, storing and
channeling water and nutrients essential for survival.

Researchers have devoted tremendous effort to engineering plants that are
more effective at these tasks in order to develop hardier forms that can
withstand drought or low-nutrient conditions.

In a new investigation, researchers from the University of Pennsylvania
have taken another step toward achieving this goal. They identified two
proteins that regulate whether a cell in plant roots forms a hair cell,
which increases surface area for absorption, or a non-hair cell. Plants
that overexpressed one of these regulators thrived despite being deprived
of a key nutrient, phosphorous.

"Normally plants respond to phosphous deprivation by becoming smaller,
which means less biomass, less food production and less seed production,"
said Brian Gregory, an associate professor in the Department of Biology in
Penn's School of Arts & Sciences and senior author on the paper. "The
intriguing thing is, by overexpressing one of these proteins we identify,
GRP8, we were able to produce plants that don't show this kind of dwarfing
nearly as significantly as normal plants under phosphorous starvation.
That's the exact phenotype we want."

Such plants, which produce more hair cells
<https://phys.org/tags/hair+cells/> and thus can more readily absorb water
from the soil, could also do well under conditions predicted to be more
prevalent under climate change, notably in widespread droughts.

The lead author of the work, published in *Developmental Cell*, is Shawn W.
Foley, a recent Ph.D. recipient in the Cell and Molecular Biology Graduate
Program of Penn's Perelman School of Medicine. Additional contributors from
Penn were Sager J. Gosai, Nur Selamoglu, Amelia C. Solitti and Fevzi Daldal
of the Department of Biology, as well as Benjamin A. Garcia of Perelman.
They teamed with Dongxue Wang and Roger B. Deal of Emory University; Tino
Köster, Alexander Steffen and Dorothee Staiger of Germany's Bielefeld
University; and Eric Lyons of the University of Arizona. Deal and Gregory
are co-corresponding authors on the paper.

The researchers initially pursued the study with the aim of determining the
difference in RNA between two very similar populations of hair and non-hair
cells in the roots of the plant species Arabidopsis thaliana. Using pure
populations of nuclei from each of the two cell types, they employed an
approach developed earlier by the lab called PIP-seq, which obtains a
complete catalog of the interactions between RNA and RNA-binding proteins,
interactions that can influence gene expression. This methodology also
allowed the team to examine the secondary structure, or folding, of all of
the cells' RNA transcripts.

"We were able to see that there were distinct differnces in RNA secondary
structure as well as differences in protein binding between root hair and
non-hair cells," said Foley.

As a next step, they identified some of the RNA binding proteins that
displayed distinct binding profiles between the cell populations and found
two that seemed significant. One, called SERRATE, "is known to play a
role," Foley said, "in alternative splicing and microRNA biogenesis,"
processes that can alter gene expression in different ways.

When they interrogated mutant plant lines with reduced SERRATE levels, they
found that plants had more, longer hair cells.

A second RNA binding protein they identified was GRP8, also a protein known
to affect plants' response to stress through regulating processes that
affect gene expression <https://phys.org/tags/gene+expression/>. Plants
that the researchers engineered to overexpress GRP8 had an increased number
of root-hair cells.

To test whether this trait affected the plant's ability to grow, they
cultivated the GRP8-overexpressing plants in phosphorous-depleted soil.
They found these plants were able to turn on genes that increase the
ability to take up and transport phosphate compared to normal plants. The
result was larger plants.

"We actually do see increased phosphate uptake as well as increased biomass
of these plants," Foley said. "We got larger, hardier plants under
phosphate starvation. We believe it's due to GRP8 functioning in the
phosphate response pathway leading to increased root hair formation."

In research now underway, the authors are testing to see whether these
findings extend to other plant species, specifically in crop plants.
Phosphate is a necessary resource for plants, and thus a component of most
fertilizers, but excess phosphate often ends up in waterways, where it can
harm aquatic ecosystems. Growing crop plants that require less phosphate
could lessen these issues.

In addition to the applications of the findings to improving the efficiency
of food production, the researchers note that their technique of
identifying the differences in RNA between two closely related cell types
can extend to systems beyond plants <https://phys.org/tags/plants/> as well.

"This study is a demonstration of our ability," Gregory said, "to use a
genome-wide approach to studying two very similar cell types
<https://phys.org/tags/cell+types/>, and then drill down and find
biologically meaningful proteins to study. It provides a model for us and
others to move forward in finding post-transcriptional regulators in
different developmental stages and stress responses and all kinds of
scenarios.

Added Foley, "Something like this really begs the questions of, If we can
have different secondary stuructre between these cells
<https://phys.org/tags/cells/> types, what other processes can RNA be
refolded during and what other processes can this help to regulate. That's
a direction the lab is going."


Read more at:
https://phys.org/news/2017-04-team-genetic-hardier-stress.html#jCp