Studies on histone chaperones and protein kinases involved in nutrient-responsive growth regulation in Arabidopsis thaliana [an abstract of entire text]

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Studies on histone chaperones and protein kinases involved in nutrient-responsive growth regulation in Arabidopsis
thaliana [an abstract of entire text]

ジェ, 琳南

北海道大学. 博士(生命科学) 甲第15308号

2023-03-23

http://hdl.handle.net/2115/89657

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theses (doctoral - abstract of entire text)

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Summary of Doctoral Dissertation
Degree requested Doctor of Life Science / Pharmaceutical Science / Soft Matter Science / Clinical Pharmacy Applicant’s name Linnan Jie

Title of Doctoral Dissertation
Studies on histone chaperones and protein kinases involved in nutrient-responsive growth regulation in
Arabidopsis thaliana
（栄養環境に応じた植物の成長制御に関与するヒストンシャペロンとタンパク質リン酸化酵素の
研究）
Since plants are non-motile organisms, they have evolved sophisticated sensing and signaling systems
that enable them to vigilantly monitor and appropriately react to the dynamic changes in their environment.
Carbon (C) and nitrogen (N), among lots of environmental elements, are essential for plants to carry out routine
and fundamental cellular functions. Both of C and N function as signaling molecules to reprograms global
gene expression levels to optimize nutrient uptake and metabolism. Recently, several studies highlighted that
histone chaperones and protein kinases play important roles in nutrient-responsive regulation, however, the
detailed mechanism still largely unknown. In this study, I investigated the function of histone chaperones
NUCLEOSOME ASSEMBLY PROTEIN1 (NAP1) proteins and protein kinases SNF1-related protein kinase
1 (SnRK1) in different C and N conditions, and aim to provide new insights into regulatory mechanisms of
nutrient-responsive growth regulations in Arabidopsis thaliana.
1. Histone chaperone NAP1 proteins affect plant growth under nitrogen deficient conditions
N availability is one of the most important factors regulating plant metabolism and growth as it affects
global gene expression profiles. Dynamic changes in chromatin structure, including histone modifications and
nucleosome assembly/disassembly, have been extensively shown to regulate gene expression under various
environmental stresses in plants. However, the involvement of chromatin related changes in plant nutrient
responses has been demonstrated only in a few studies to date. In this study, I investigated the function of
histone chaperone NAP1 proteins under N deficient conditions in Arabidopsis. In the nap1;1 nap1;2 nap1;3
triple mutant (m123-1), the expression of N-responsive marker genes and growth of lateral roots were
decreased under N deficient conditions. In addition, the m123-1 plants showed a delay in N deficiency-induced
leaf senescence. Taken together, these results suggest that NAP1s affect plant growth under N deficient
conditions in Arabidopsis.
2. Plant fuel sensor SnRK1 functions in sugar responsive modulation of immunity in Arabidopsis thaliana
For plants, sugar does not only serve as an energy source and carbon skeleton, but also functions as
signaling molecules to optimize plant growth and resistance to multiple environmental challenges. Plants often
encounter pathogen challenge in nature, and thus available sugar resources need to be balanced between
defense and growth. Recent studies claimed the crosslink between sugar and immune signals in plants,
however the underlying molecular mechanisms are still largely unknown. In this study, I found that expression
of several defense marker genes was enhanced when sugar availability is increased in Arabidopsis thaliana.
In addition, I revealed that the plant fuel sensor SNF1-related protein kinase 1 (SnRK1) is involved in sugar
responsive immune responses partly dependent on a phytohormone salicylic acid pathway. In the
dexamethasone -induced snrk1α1isnrk1α2 knockdown mutant (snrk1) plants, the expression levels of sugarresponsive defense marker genes were increased whereas the increasement was suppressed by mutation on
SA-related genes. Besides, snrk1 plants displayed a higher resistance against Pseudomonas syringae pv.
tomato DC3000. Taken together, these results suggest that SnRK1 functions in sugar responsive modulation
of defense marker genes’ expression and is a negative regulator of plants defense response to pathogen attack
in Arabidopsis thaliana. ...

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