New study shows how plants regulate their growth-inhibiting hormones to survive

Date:
July 15, 2020
Source:
Nagoya University
Summary:
Scientists have, for the first time, observed one of the natural
mechanisms underlying the regulation of the levels of growth
inhibiting hormone in plants. This mechanism had been hitherto
seen in bacteria, but its discovery in plants will enable novel
ways of increasing crop productivity globally.



FULL STORY ==========================================================================
In a world with a consistently growing population and a climate
crisis, food shortage is a looming threat. To alleviate this threat,
crop scientists, botanists, genetic engineers, and others, have been
exploring ways of boosting crop productivity and resilience. One way
to control plant growth and physiology is to regulate the levels of "phytohormones" or plant hormones.


========================================================================== However, much remains to be known about the mechanisms that underlie
this hormonal regulation in plants, limiting advancement in this
direction. Now, in a study led by Nagoya University Japan, a team of
scientists has discovered, using rice plants as the study model, that
a process called "allosteric regulation" is involved in maintaining the phytohormonal balance in plants.

Their findings, published in Nature Communications, could hold the key
to significantly advancing the research on plant growth and development, providing a potential solution for food security.

Plants survive by adapting their development and physiology to their surrounding environments by controlling the levels of enzymes driving
the synthesis of two phytohormones, gibberellin and auxin. Enzymes are
proteins that bind to one or more reactant chemicals and speed up a
reaction process.

The binding site is called the activation site. In 1961, it was discovered
that in bacteria, enzyme activity is enhanced or inhibited via allosteric regulation, which essentially is the binding of a molecule called the "effector" at a site other than the active site of the enzyme. In
allosteric regulation, the structure of the enzyme changes to either
support or hinder the reaction that the enzyme enables.

Professor Miyako Ueguchi-Tanaka of Nagoya University, lead scientist
in the team that has now observed allosteric regulation in plants
for the first time, explains their research findings, ''We used a
technique called X-ray crystallography and found that, as molecules of
the enzymes (gibberellin 2- oxidase 3 [GA2ox3], and auxin dioxygenase
[DAO]) bind to gibberellin and auxin (respectively), they interact among themselves and form 'multimeric' structures, comprising four and two units respectively. As the amounts of gibberellin and auxin increase, so does
the rate of multimerization of the enzymes. And multimerization enhances
the activity of the enzymes, enabling greater degradation of gibberellin
and auxin. Synchronous structural changes and activity enhancement
are typical of allosteric-regulation events." The scientists further
carried out "phylogenetic" analysis of GA2ox3 and DAO, which revealed
that plants independently developed this hormone regulation mechanism
at three separate time-points over the course of the evolutionary process.

Enthusiastic about the future prospects of these findings, Prof
Ueguchi says, "The activity control system revealed here can be used to artificially regulate the activity of the growth inactivating hormones
in plants. As a result, rice crop productivity can be improved and
high-biomass plants can be produced in the event of food shortage or an environmental crisis." Of course, this study is only a stepping stone
for now, and much remains to be done to see how the findings of this
study can be applied practically in agricultural lands. However, these
findings certainly are encouraging, and they signal the coming of a new
era of sustainable development fueled by biotechnological advancements.


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


========================================================================== Journal Reference:
1. Sayaka Takehara, Shun Sakuraba, Bunzo Mikami, Hideki Yoshida, Hisako
Yoshimura, Aya Itoh, Masaki Endo, Nobuhisa Watanabe, Takayuki
Nagae, Makoto Matsuoka, Miyako Ueguchi-Tanaka. A common
allosteric mechanism regulates homeostatic inactivation of
auxin and gibberellin. Nature Communications, 2020; 11 (1) DOI:
10.1038/s41467-020-16068-0 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200715095452.htm

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