Release Subtitle: Scientists study the 24-hour pattern of
magnesium intake in a rice plant to see if the photosynthetic efficiency
of the plant can be improved
Release Summary Text:
Many processes of photosynthesis, including the intake of magnesium,
follow a pattern of variation over 24 hours. In a new study, scientists
from Okayama University, Japan and Fujian A & F University, China,
tested the effect of this variation on the efficiency of photosynthesis
in rice plants. Their findings suggest potential candidates for
modification for increasing the yield of rice crops, thereby offering a
potential solution to the global food shortage.
Full text of release:
The fundamental process that arguably forms the backbone of life on
earth is photosynthesis; every organism is directly or indirectly
dependent on this process. On paper, the process is simple: plants (and
other organisms that have “chloroplasts,” the structures where
photosynthesis takes place, and give the characteristic green color to
leaves) convert solar energy into chemical energy that helps them grow
and flourish, and other “higher” organisms depend on these plants, or on
organisms that feed on these plants, for their own sustenance, and so
on.
But in practice, and especially at this point in biological history,
this process is not so straightforward. The human population is growing
at an unprecedented rate; the resources we have are not enough to feed
the billions of people on earth today. While policymakers and
politicians are trying to optimize the use of existing resources,
scientists are doing their bit by figuring out how to improve the
resources by exploring whether the natural process of photosynthesis can
be modified through the latest technologies to ultimately improve the
yield of food crops.
A team of scientists led by Prof Jian Feng Ma from Okayama University,
Japan, and Prof Zhichang Chen from Fujian A & F University, China,
also set out to explore photosynthesis, but they decided to do this with
a twist: while current research predominantly focuses on trying to
modify the direct chemical reactions involved in photosynthesis, the
team decided to look at the “diel” variations—or the variations that
occur over a periodic cycle of 24 hours—in photosynthesis.
That many processes of photosynthesis exhibit 24-hour variations
shouldn’t come as a surprise, given that the entire process is dependent
on sunlight. Apart from external light-dark conditions, these diel
changes can also be driven by internal genetic mechanisms.
But what exactly did these scientists look at? “Our study focused on
magnesium, and for a diverse set of reasons,” explains Prof Ma.
“Magnesium is an essential macronutrient for plants, but around 15–35%
of total magnesium intake is allocated to chloroplasts, where it
functions not only as a structural element of chlorophyll but also as an
activator for a number of photosynthetic enzymes.” This meant that
studying the diel changes in magnesium can shed light on an important
functional aspect, and potential target for manipulation, of
photosynthesis.
Through gene studies in the rice plant (the results of which are
published in Nature Plants), the researchers decided to narrow in on a
magnesium ion transporter OsMGT3, found in chloroplasts, and are known
to be rhythmically expressed in “mesophyll” cells, the cells specialized
for photosynthesis.
They created genetically modified rice plants in which the gene that
gives rise to OsMGT3 was absent; they found that these plants showed
significantly reduced uptake of magnesium and reduced amplitude of free
magnesium ion fluctuations in chloroplasts. This resulted in a decrease
in the activity of “ribulose 1,5-bisphosphate carboxylase,” a
fundamental enzyme of photosynthesis, naturally leading to a decline in
the photosynthetic rate. Next, through genetic engineering techniques,
they caused the excessive production of OsMGT3 in mesophyll cells in
normal rice plants and found that the photosynthetic efficiency and
growth improved in these plants.
These experiments proved that OsMGT3 partially controls the magnesium
fluctuations in chloroplasts, and that these fluctuations may contribute
to magnesium-dependent enzyme activities for photosynthesis over the
daily cycle.
So where does this leave us in terms of optimizing crop yield and
feeding the masses? Prof Ma states that the findings open up hitherto
unexplored avenues, remarking, “Our studies put magnesium in the
limelight. Modifying the magnesium input into chloroplasts could be a
potential approach to improving photosynthetic efficiency in plants and
can eventually improve crop yield.”
This study, along with future studies that would demonstrate how exactly
magnesium should be targeted, could be a potential answer to the global
food shortage.
Release URL: https://www.eurekalert.org/pub_releases/2020-07/ou-did071020.php
Reference:
Title of original paper: Diel magnesium fluctuations in chloroplasts contribute to photosynthesis in rice
Journal: Nature Plants
DOI: http://dx.doi.org/10.1038/s41477-020-0686-3
Contact Person: Jian Feng Ma
E-mail: maj(a)rib.okayama-u.ac.jp
For inquiries, please contact us by replacing (a) with the @ mark.
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