硫黄不足時のグルコシノレート分解に働くβ-グルコシダーゼの同定と植物の生長における意義

概要

九州大学学術情報リポジトリ
Kyushu University Institutional Repository

Identification of β-glucosidases responsible
for glucosinolate catabolism under sulfur
deficiency and the significance of this process
in plant growth
張, 柳

https://hdl.handle.net/2324/7157400
出版情報：Kyushu University, 2023, 博士（農学）, 課程博士
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Name

：張

柳 (ZHANG LIU) チョウ リュウ

Title

： Identification of β-glucosidases responsible for glucosinolate catabolism
under sulfur deficiency and the significance of this process in plant growth
(硫黄不足時のグルコシノレート分解に働くβ-グルコシダーゼの同定と植
物の生長における意義)

Category： Kou
Thesis Summary
Sulfur (S) is one of the macronutrients necessary for plant growth and development. The primary source of S
in the environment is inorganic sulfate. Sulfate can be absorbed into plants and assimilated into organic S
compounds. This assimilatory process is defined as primary S metabolism, via which the primary
S-containing metabolites, such as cysteine and glutathione, are produced. The plants belonging to the
Brassicales order can produce a group of specialized S-containing metabolites named glucosinolates (GSL).
Previous studies revealed that when plants face S deficiency (−S), they stimulate the primary S metabolism
closely related to their survival. Instead, plants repress the GSL biosynthesis and would stimulate their
catabolism. GSL catabolism is the famous “mustard oil bomb” in plant defense response against insect attack.
However, the roles of this catabolic process under nutrient stress have not been elucidated yet.
GSL catabolism is catalyzed by ß-glucosidases (BGLUs). The increased expression level of BGLU28
and BGLU30 under −S indicated their roles in triggering GSL catabolism under this nutrient stress. To verify
their function, we generated the double disruption lines of BGLU28/30 (bglu28/30) using Arabidopsis as
material. We observed that bglu28/30 accumulated a higher level of GSL but reduced cysteine and
glutathione levels under −S. Furthermore, bglu28/30 displayed obvious growth retardation under −S. These
results confirmed that BGLU28 and BGLU30 were responsible for GSL catabolism under −S. And very
possibly, GSL can function as S storage compounds. Namely, upon their catabolism under −S, S in GSL is
released and recycled to synthesize primary S-containing compounds essential for plant growth.
Motivated by these observations, as GSL profiles in plants vary among growth stages and organs, we
further

verified

the

potential

contribution

of

BGLU28/30-dependent

GSL

catabolism

at

the

reproductive-growth-stage plants. In this study, we further assessed the growth, metabolic, and
transcriptional phenotypes of mature bglu28/30 double mutants grown under different S conditions. Our
results showed that compared to wild-type plants grown under −S, mature bglu28/30 mutants impaired their
growth and increased GSL levels in their reproductive organs and rosette leaves of the before-bolting plants.
In contrast, the levels of primary S-containing metabolites, glutathione, and cysteine decreased in mature
seeds. Furthermore, the transport of GSL from rosette leaves to the reproductive organs was stimulated in the
bglu28/30 mutants under −S. Transcriptome analysis revealed that genes related to other biological processes,
such as ethylene response, defense response, and plant response to heat, responded differentially to −S in the
bglu28/30

mutants.

Altogether,

these

findings

broadened

our

understanding

BGLU28/30-dependent GSL catabolism in plant adaptation to nutrient stress.

of

the

roles

of