fungai nutrient acquisition.pdf

University of Agricultural Sciences, GKVK,
Bengaluru
Department of Plant Pathology
Seminar-1
Siddu Lakshmi Prasanna
PALB 7314
Sr. M.Sc (Agri)
Title: Mechanisms of nutrient acquisition and utilization
during fungal infections of leaves
9/12/2022 1
Siddu lakshmi Prasanna, PALB 7314

INTRODUCTION
• Nutrient - Any chemical substance required for metabolism or
development.
• Nutrient Acquisition - uptaking of nutrients from its own
host.
•
• + =
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• Biotrophs - need living tissue to survive.
Ex: Rusts, Powdery mildews, Downy mildews.
• Necrotrophs - kill the host to acquire nutrients.
Ex: Leaf spots etc.,
• Hemibiotrophs - both biotrophic and
necrotrophic phase.
Ex: Magnaporthe oryzae,
Colletotrichum sps etc.,
General Feeding Strategies
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Divon et.al., 2006
Divon et al., 2007
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Biotroph??
Necrotroph??
Hemibiotroph??
What
makes it to
be a
Genome, genetic regulators will determine the
metabolic regulation of the fungi.
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• Genomes of the obligate biotrophs are reduced for genes encoding
proteins involved in primary metabolism, nitrogen assimilation,
carbohydrate active enzymes (CAZys), cell wall degrading enzymes
(CWDEs) etc.,
whereas, necrotrophs carry genes for assimilating nitrate and also
encode for putative plant cell wall degrading enzymes.

Divon et al., 2007
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Metabolic regulation at genetic
level
• All pathogenic lifestyles involve in nitrogen and carbon
acquisition and assimilation from the host.
• Global regulators – Ensure the preferential utilization of
nutrients rather than less preferable sources.
• Pathway-specific regulators – Ensure that genes of a required
catabolic pathway are only expressed in the presence of the
appropriate inducer.
• Ex: For M. oryzae the preferred carbon and nitrogen sources
are glucose and ammonia respectively.
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Fernandez et al., 2014

• Different genetic regulators of foliar pathogens are as
follows:
➢ Global nitrogen regulators
➢ Pathway-specific nitrogen regulators
➢ Global carbon regulators
➢ Pathway-specific carbon regulators
9/12/2022 Siddu lakshmi Prasanna, PALB 7314 8
Glucose
CCR
Alternative
carbon source
NH4
+
Nut1
Alternative
nitrogen source

Global nitrogen regulators
• Global nitrogen metabolism is regulated by wide domain,
positive acting GATA-family transcription factors like
AreA of Aspergillus nidulans and
Nit2 of Neurospora crassa
which ensure the utilization
of NH4
+ & L-glutamine over
less favourable nitrogen
compounds.
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• AreA / Nit2 is required for the expression of genes required for
alternative nitrogen source utilization.
• A. nidulans areA mutant strains can use only ammonium or L-
glutamine as sole nitrogen sources.
• Orthologous AreA/Nit2 encoding genes have been identiﬁed in
the genomes of biotrophic, necrotrophic, and hemibiotrophic
fungal groups.
• Ex: Cladosporium fulvum - Nrf1
Ustilago maydis - Nit2
Colletotrichum lindemuthianum - Clnr1
Magnaporthe oryzae - Nut1
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Pathway specific nitrogen regulators
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• Ex:
In M. oryzae the NIRA/NIT4
ortholog NIR1, encodes a
pathway specific activator
required for growth on
nitrate and nitrite which is
dispensable for pathogenicity.

The Target of Rapamycin (TOR)
Pathway
• TOR pathway activated mainly during sufficient nutrient
conditions.
• Inhibition of TOR by rapamycin or nutrient starvation causes
a nutrient stress response resulting
in translation initiation inhibition,
cell cycle arrest, autophagy.
• Hence, TOR is a master
regulator of the switch from
catabolism to anabolism.

• Ex: In yeast Mig1 is a phosphorylation target of Snf1 & a
DNA binding protein which
negatively regulates glucose
repressed genes.
• In filamentous fungi, CreA shares
some sequence similarity with
Mig1.
Global carbon regulators

Pathway-specific carbon regulators
• Ex: In M.oryzae Xlr1 is a Zn(2)-Cys(6) zinc ﬁnger
transcription factor which controls the expression of xylose
catabolizing genes during growth on D-xylose.
• Loss of Xlr1 function restricted growth on xylose-containing
media, but the utilization of xylan, a sugar present in plant cell
walls, was not affected.
• This suggests that, unlike some other fungi, M. oryzae has
separate control systems for xylose and xylan degradation.
• As a consequence, Xlr1 strains were not affected in
pathogenicity on rice or barley, and xylose metabolism is not
an important metabolic pathway in the host.
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Integrating Carbon & Nitrogen
Metabolism
• Ex: Both carbon and nitrogen metabolism in TPS1 dependent
manner in M. oryzae.
• Two pathogenicity genes SPM1- serine protease,
PTH11 –plasma membrane protein
which are under the control of
Nut1 and expressed in response
to glucose regardless of
nitrogen source.
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Hypothesis: Nitrogen regulated processes might also contribute to the
colonization of rice cells by M. oryzae.
Objective: To determine the effect of NMO2 gene for tolerating
against nitrooxidative stress response, nitrate utilization, development
of rice blast disease and to suppress the cell defences.
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9/12/2022 18
Guzman et al., 2017
Nitroalkanes Carbonyl + Nitrite
compounds

9/12/2022 19
Guzman et al., 2017
Expression of NMO2 was Nut1-dependent
during early biotrophy.

Guzman et al., 2017

9/12/2022 21
Guzman et al., 2017
NMO2 is reguired for
nitrate and nitrite
utilization

Guzman et al., 2017

NMO2 is required for tolerating nitrooxidative stress
Guzman et al., 2017

Guzman et al., 2017

Guzman et al., 2017
NMO2 gene is dispensable
for pathogenecity

Guzman et al., 2017
NMO2 gene required to suppress plant cellular defences

Objective: To examine the effect of nitrogen availability
on fungal morphogenesis and pathogenecity.
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Spray inoculation
Drop inoculation
M3s rich medium
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Horowitz et al., 2006
Wild type Ca5 mutant

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Ca5 mutant
Wild type
Growth of conidia
on minimal media
lacking nitrogen
source
When provided an
external nitrogen
source

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Wild type Ca5 mutant

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Predicted NIR1 protein of C. acutatum belongs to
Zinc cluster domain or not???

Growth on minimal media as sole nitrogen sources
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Primers used for qRT-PCR
analysis

Expression analysis of genes through qRT-PCR

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Expression profile of nitrogen
metabolism related genes
Pathogenecity of different
C. acutatum strains

h
Objective: To examine the role of SNF1 from M. oryzae in
catabolite repression, regulation of CWDE expression and
cellular development related to pathogenesis.
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Clustal W alignment of
aminoacid sequences of
different fungi
Yi et al., 2008

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Yi et al., 2008
Phylogenetic analysis
of snf1

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Yi et al., 2008
Mutants produced through gene knock-out strategies

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Yi et al., 2008
Growth of ∆mosnf1 mutant and complementation
transformant (CP16) on different carbon source media

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Yi et al., 2008
Expression of genes encoding
cell wall degrading enzymes
Pathogenecity of mosnf1 and
∆mosnf1 mutants

Yi et al., 2008

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Yi et al., 2008
Sporulation defects of conidiophore and conidia
Conidiophore
Conidia

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Yi et al., 2008
Reintroduction of the MoSNF1 gene into ∆mosnf1 mutant :

9/12/2022 45

fungai nutrient acquisition.pdf

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fungai nutrient acquisition.pdf