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HGT ID 1
-
34
(Figs S1.1
-
S1.30)

GenBank
Acc.

/
JGI
d
atabase
protein ID

Reported
in Richards
et al 2006

Annotation

Evidence of
Signal peptide
and
Secret
ion

1 (S1.1)

EEY57756

Yes (named
AraJ)

Annotation by similarity search
(1
-
3)

suggest
s

that
this HGT
encodes

a
major
facilitator s
uperfamily (MFS)

transporter
.
The MFS transporters are single
-
polypeptide secondary carriers capable of transporting small solutes in response
to chemi
-
osmotic ion gradients
. T
he MFS is a la
rge and diverse group of
secondary transporters and can facilitate the transport across cytoplasmic or
internal membranes of a variety of substrates including ions, sugar phosphates,
drugs, neurotransmitters, nucleosides, amino acids, and peptides
(1, 2)
.
KASS
analysis suggests this protein sequence has the highest affinity with saccharide
monomer transporters
.

N

2
(S1.2)

82760
(
P.ramorum
)

Yes (named
esterase/lipa
se



see Fig.
S3B
(4)
)

T
his HGT

candidate

encodes

an extracellular pr
otein with a putative

esterase/lipase domain. The functional role of esterases and lipase enzymes is
difficult to decipher based on homology searches because substrate specificity
often depends upon small changes in amino acid sequences and these enzyme
fa
milies have relatively few functional studies compared to the complexity of th
e
protein families
(5, 6)
. However, the amino acid sequence has strong sequence
similarity to
carotenoid ester lipase enzymes of the fung
us
Pleurotus sapidus
which have been shown to perform
efficient hydrolysis of xanthophyll esters
(7)

and

are

therefore

potentially

important for processing

xanthophyll
caretenoids

found in plant tissues.


KASS data
base analysis
also
demonstrated that this gene has strong similarity
to enzymes that function in sterol and lipid degradation. Interestingly
,

many
oomycetes depend on extr
acellular sources of sterol and fatty acids, and the
supply of these metabolites play

a role in determining

the transition

of oomycetes

through
different

lifecycle
stages
(8, 9)
.

Although these putative extracellular
enzymes may have a number of roles in releasing long chain fatty acids and
terpeno
ids from a range of
plant derived
substrates (e.g. carotenoids
, suberin,
cutin
).


This is one of
four separate putative HGTs
of
esterase/lipase domain
-
containing
extracellular proteins. It is difficult to predict the function of these proteins
,

but
extrace
llular lipases have been shown to be important pathogenic phenotypes
Y

involved in the detection and breakdown of plant waxy cuticle
(10
-
12)

which may
represent an important metabolic resource for sterol and long chai
n fatty acids

for oomycete plant pathogens
.

3
(S1.3)

AAM48174.
1

Yes (named
GalM)

This
HGT
putatively encodes

an
aldose 1
-
epimerase
(EC 5.1.3.3)
.
This enzyme
catalyses conversion of


-
D
-
glucose to


-
D
-
glucose and

-
D
-
galactose to

-
D
-
galactose
(13)

which can both be fed into glycolysis. Both

-
D
-
glucose and

-
D
-
galactose are major components of the plant cell wall with

-
D
-
galactose (

-
D
-
galactan) being a major component of pectin.
The
enzyme
may therefore be

involved in
plant cel
l wall degradation by oomycete pathogens.


This
HGT
gene was recovered in a gene dense
10.8 kb BamHI fragment of the
P
.

sojae
genome project
tightly linked to

three gene copies of a n
ecrosis inducing
protein
-
encoding gene

which is also a fungal derived HGT

(see
HGT 20

below)
(14)
.

N

4 (S1.4)

71178

(
P.ramorum
)


This
HGT
putatively encodes

an
α
-
ketoglutarate dependent xanthine
dioxygenase (XanA
),

an enzyme function only previously known from fungi and
involved in hydr
oxylation of xanthine to uric acid
(15)
). The fungi
and oomycete
genes form
a
discrete clade
,

distantly related to the prokaryotic homologues (Fig.
S1.4) which are of the TauD protein family.
TauD from
E. coli

is an

α
-
ketoglutarate
-
dependent

taurine dioxygenase (
EC

1.14.11.17)
. This enzyme
catalyses the oxygenolytic release of sulfite from taurine. In fungi
,

XanA knock
-
out experiments in different fung
al species

have demonstrated that this gene
encodes a protein impor
tant for
xanthine utilization because these knock
-
out
strains
fail to convert xanthine to uric acid when xanthine

dehydro
genase activity
is also deleted or

inhibited
(15, 16)

and when these fungi are grown on xanthi
ne
as a sole source of nitrogen.
No alternative purines effectively substitute for
xanthine as a substrate for this enzyme reaction
,

suggesting
that the

enzyme is
highly substrate
-
specific
(17)
.
X
anthine is present
in plant and animal cells and is
a
product o
f

purine degradation
.

Interestingly this represents an alternative
pathway
for xanthine breakdown

to that commonly found in other taxa
,
where
xanthin
e is broken down by a pathway composed of unrelated protein families
contain
ing

the molybdopterin cofactor Moco
(15)
.
The

predicted

function and
taxon distribution
of this HGT candidate family
suggest
s

that th
e
enzy
me
may

represent an important
adaptation for

nitrogen

scavenging
in fungal and
oomycete

osmotrophs
.


N

5 (S1.5)

EEY56552


Our a
nnotation suggests this HGT
candidate encodes a

dehydrogenase/reductase (MDR)/zinc
-
dependent alcohol dehydrogenase
-
like
N

family p
rotein.

This group is a member of the medium chain
dehydrogenases/reductase (MDR)/zinc
-
dependent alcohol dehydrogenase
-
like
family, but lacks the zinc
-
binding sites of the zinc
-
dependent alcohol
dehydrogenases. This is a diverse group of proteins related t
o the first identified
member, class I mammalian ADH. MDRs display a broad range of activities and
are distinguished from the smaller short chain dehydrogenases (~ 250 amino
acids vs. the ~ 350 amino acids of the MDR)
(1)
. Phylogenetic
a
nalysis of other
alcohol dehydrogenase
-
encoding

genes has demonstrated multiple HGT events,
suggesting that other alcohol dehydrogenase enzymes have replaceable
functional roles and have undergone numerous replacements by HGT
(18, 19)
.

6 (S1.6)

72257

(
P.ramor
um
)


Annotation
suggests this
HGT
candidate
protein
has strong similarity to the
extracellular quercetin 2,3
-
dioxygenase (
EC 1.13.11.24) identified from
filamentous ascomycetes (e.g.
(20, 21)
).
Quercetin 2,3
-
dioxyge
nase is a type 2
copper
-
dependent enzyme
,

which
is able to disrupt the O
-
heteroaromatic ring of
flavonols, yielding the corresponding depside (phenolic carboxylic acid ester


i.e.
2
-
p
rotocatechuoyl
-
phlorogucinol carboxylic acid
) and carbon monoxide
(22)
.
Quercetin is a naturally occurring flavonoid compound found in most plant
tissues and also a product of rutin breakdown.

Quercetin 2,3
-
dioxygenase is
produced by various filamentous fungi when grown on the
complex a
romatic
compound

rutin

as sole carbon and energy source
(20, 21, 23)

suggesting this
enzyme is part of an important pathway for
breakdown of
plant tissues.

Y

7 (S1.7)

EEY52979


Annotation by similarity search
(1
-
3)

suggests this
HGT
candidate encodes
an
extracellular
α
-
L
-
rhamnosidase (EC 3.2.1.40


glycosyl hydrolase
family
78
(24)
).
This putative enzyme catalyses the
hydrolysis of terminal

non
-
reducing α
-
L
-
rhamnose
i.e. hydrolyzing
α
-
1,2 and
α
-
1,6 linkages
(25, 26)
.
L
-
r
hamnose is an
abundant monosaccharide, a common constituent of glycolipids

(e.g.
rhamnolipids found in some bacteria)

and glycosides,

such as plant pigments,
pectin, gums or biosurfactants.
Pectin from plant cell walls, contains
rhamnogalacturonan, consisting of rhamnose and galacturonate as the main
-
chain and therefore this
enzyme is important to many plant
-

associated fungi for
modify
ing and/or degrading rhamnose
-
related compounds
,

including the plant
cell wall
(25, 26)
.
Metabolic reconstruction based on the
published
oomycete
genomes demonstrates that there
i
s no identifiable rhamnose utilizati
on pathway
,

suggesting
that

oomycetes do not
normally
metaboli
z
e rhamnose for energy
.

The
HGT acquisition

may

function as
a plant cell wall degrading enzyme
.


A
nalysis of
P. infestans
microarray data
(27)

suggests

that one gene from this
Y

HGT family showed up
-
regulation
after five days
infection of plant tissue

(
t
-
test; P
value

at <0.1

-

borderline
).

8 (S1.8)

EEY63463


This HGT candidate family encodes a member of
l
actonohydrolase/
gluconolactonase.
L
actonohydrolas
es are intramolecular ester
bond
-
hydrolyzing enzymes.

Lactone compounds are cyclic compounds
possessing intra
-
molecular ester bonds and are widely distributed in nature
(28)
.

Lactonohydrolases have been implicated in ascorbate biosynthesis and also the
breakdown of dihydrocoumarin and other plant
-
associated aromatic lactones
(20)
.

N

9 (S1.9)

EEY64355



Annotation suggests this HGT
candidate encodes

an

extracellular
glucooligosaccharide oxidase (
EC 1.1.99.B3)

which
putatively
catalyse
s

carbohydrate oxidation to the corresponding lactones. A similar gluco
-
oligosaccharide oxida
se (GOOX) from the fungus
Acremonium strictum

has
been shown to perform
oxidization of a variety of carbohydrates with the
concomitant reduction of molecular oxygen to hydrogen peroxide. This enzyme
was shown
to use
D
-
glucose, maltose, lactose, malto
-

and
cello
-
oligosaccharides, cellobiose
as

substrates. Demonstrating a broad substrate
specificity of GOOX, particularly toward oligosaccharides
(29, 30)
.

Y

10 (S1.10)

EEY59160


Our a
nnotation
s

suggests this HGT
candida
te encodes

an extracellular
unsaturated rhamnogalacturonyl hydrolase
(g
lycosyl
hydrolase f
amily 88
-

EC:3.2.1.
-
). This enzyme catalyses the
random hydrolysis of (1

4)
-
α
-
D
-
galactosiduronic linkages in pectate and other galacturonans e.g.

hydrolysis of
unsat
urated rhamnogalacturonan disaccharide to yield unsaturated D
-
galacturonic acid and L
-
rhamnose
.

Potentially

an important component of pectin
and plant cell wall degradation.
Metabolic reconstruction based on the three
Phytophthora

genome projects demonstra
tes that a standard galactouronide
utilisation pathway was absent. Further searches identified a partial alternative
(fungal) galact
o
uronide metabolic pathway, a four enzyme pathway found in
some fungi utilized to break

down plant
cell wall
s

(31, 32)
,


Analysis of
P. infestans
microarray data
(27)

suggests

that one gene from this
HGT family showed up

-
regulation after
five days
infection of plant tissue

(
t
-
test
,
P value

at <0
.1

-

borderline
).

Y

11 (S1.11)

83543

(
P.ramorum
)


Annotation by similarity search
(1
-
3)

suggests this HGT
encodes

a putative
transcription factor (
pfam04299). In
Bacillus subtilis
, family member PAI 2/ORF
-
2
was fou
nd to be essential for growth
encoding

a novel transcriptional
-
regulat
or

involved in glucose repression
(33)
.

N

12 (S1.12)

85044

(
P.ramorum
)


Our a
nnotation
s

suggests this HGT
candidate

is a
member of a large prot
ein
family including: 1) 3
-
octaprenyl
-
4
-
hydroxybenzoate carboxy
-
lyase
which

catalyzes the third step in the biosynthesis of ubiquinone, and 2)
Phenylphosphate

carboxylase
,

a carbon
-
carbon l
yase which eliminates or adds
carboxy
-
group
s

to
phenols

(34)
.

Metabolic modeling in the three
Phytophthora

genomes

suggests that ubiquinone pathway is performed by the alternative
eukaryotic synthesis pathways


suggesting this prokaryote
-
like UbiD protein
seems to be redundant in
relation to ‘prokaryote’ ubiquinone synthesis as the
other pathway enzyme steps are missing. The enzyme may participate in
production of precursors and scavenging intermediates for ubiquinone synthesis
and may therefore
be involved in degradation of phenyl
propanoids (lignino
-
stilbene)
which are

bi
-
products of lignin and suberin breakdown

from plant cell
walls
.

N

13 (S1.13)

EEY53137


Annotation by similarity search
(1
-
3)

suggests this HGT
candidate encodes

a
phosphat
idylinositol transfer protein
,

involved in transport of
phospholipids

from
their site of synthesis in the
endoplasmic reticulum

and
Golgi

to other
cell
membranes

(35)
.

N

14 (S1.14)

133521

(
P. sojae
)


Annotation suggests this HGT
candidate encodes

an extracellular
hypothetical
protein
with sequence similarity to prokaryote secretory lipases.

It is difficult to
predict the function of this protein, as the esterase/lipase family is a highly
complex gene family.
Interestingly
,

many oomycetes depend on extr
acellular
sou
rces of sterol and fatty acids, and the supply of these metabolites plays a role
in determining

the transition

of oomycetes

through
different

lifecycle
stages
(8,
9)
. Although these putative extracellular enzymes ma
y have a number of roles in
releasing long chain fatty acids and terpenoids from a range of substrates (e.g.
carotenoids
, suberin, cutin
).


This is one of
four separate transfers
of
esterase/lipase domain containing
extracellular proteins. It is difficult
to predict the function of these proteins but
extracellular lipases have been shown to be important pathogenic phenotypes
involved in the detection and breakdown of plant waxy cuticle
(10
-
12)
, which may
represent an

important metabolic resource for sterol and long chain fatty acids

for oomycete plant pathogens
.

Y

15 (S1.15)

142730

(
P.sojae
)


Our annotations

suggests this HGT
candidate encodes a

conserved hypothetical
protein
with sequence similarity to the esterase/
lipase protein domain family
.
A
putative gene family

that may play roles in

releasing long chain fatty acids and
terpenoids from a range of

plant derived

substrates (e.g. carotenoids
, suberin,
N

cutin
).


One

of
four separate transfers
of
esterase/lipase doma
in containing proteins

16 (S1.16)

EEY68514


Annotation

suggests this HG
T encodes a xylitol dehydrogenase / s
orbitol
dehydrogenase (EC 1.1.1.9/ EC 1.1.1.14)
. T
his gene family includes
broad
-
spectrum reversible oxidoreductases of sugar alcohols e.g. sorbi
tol to fructose,
with NAD reduction
(36, 37)
. Interestingly in fungi, sugar alcohols, such as
mannitol, arabitol, and glycerol, accumulate and have a number of different
cellular functions. These include maintaining

osmotic balance, generating turgor
in appressoria, and quenching reactive oxygen species

(38)
. Sugar alcohols
may form in plant
-
pathogenic fungi when

-
fructosidases
convert

plant
-
derived
sucrose to fructose, whic
h is converted to sorbitol by sorbitol dehydrogenase. It
is unclear what function this enzyme plays in
Phytophthora

because

oomycetes
are thought
not
to accumulate sugar alcohols
,

such as sorbitol
(39)
,
and
therefore a number of alternative roles are suggested
(38)
.
Oomycete g
ene
expression

patterns

and
enzyme
activity
have
been shown to

be associated with
sporulation. Furthermore,

the enzyme displayed similar activities when sorbitol,
xylitol, sorbitol,

or glycerol was used as a su
bstrate
(38)

suggesting that this HGT
represents a useful enzyme for reconfiguring a range of sugars which can then
ultimately be fed into glycolysis.

N

17 (S1.17)

EEY55544


Annotation suggests th
at this

HGT
candid
ate encodes

a
n

extracellular arabinan
-
endo
-
1,5
-
α
-
L
-
arabinosidase (g
lycosyl hydrolases family 43)
, w
hich catalyses
endohydrolysis of (1

5)
-
α
-
arabinofuranosidic linkages
. Arabinans are found in
hemicellulose and

consist of a backbone of
-
1,5
-
linked L
-
arabinofuranosyl
residues,

some of which are substitut
ed with
-
1,2
-

and
-
1,3
-
linked side

chains.
This enzyme catalyses breakdown of the arabinan backbone
(40, 41)

and
therefore is a critical acquisition for digestion of plant cell wall
because

it acts
synergistically w
ith a number of other plant cell wall
degrading
enzymes.


Metabolic reconstruction based on the oomycete genomes demonstrates that no
identifiable arabinose utilization pathway suggesting the oomycetes analysed
here do not metabolise arabinose for energy a
nd classical culture
-
based studies
have demonstrated that arabinose is a poor sugar source for
Phytophthora
species
(39)
. We therefore hypothesise that this HGT acquisition functions as
a
secreted
enzyme for the breakdown of plant cell walls.

Y

18 (S1.18)

EEY59913

Yes (na
med
CodB)

Our a
nnotation
s

suggests this HGT
encodes
a

transporter protein. This
family
consists of bacterial and fungal transporters for purines and pyrimidines.
In
N

filamentous fungi, apart from their direct use in nucleic acid or nucleotide
biosynthesis,
purines can also be used
(
through their oxidation to ureides and
eventually to urea and ammonium
)

as nitrogen sources. The expression of
fungal genes encoding purine
-
specific transporters or enzymes involved in
purine catabolism is usually induced by purin
es and repressed when a primary
nitrogen source
,

such as ammonium or glutamine
,

is available
(42, 43)
. This
result is intriguing because

Phytophthora
metabolic network analysis
demonstrated that all three oomycetes
have retained a
functional
purine and
pyrimidine biosynthesis pathway, suggesting that these parasit
ic oomycetes

do
not need to acquire nucleobases from the environment. This suggests that th
e

transporter has additional transport functions or is used to ac
quire purines

from
plant breakdown

to provide nitrogen.



Interestingly
,
BLASTp (ref_seq database) suggest that this transporter also has
homology
to a
pyridoxine transport protein in Saccharomycotina yeast species
.
Metabolic network analysis demonstrated
that
the
Phytophthora
species
analysed

lack
pyridoxal 5'
-
phosphate synthase (EC
1.4.3.5)
,
an integral step in
the synthesis of sterols
,

suggesting th
at this

sub
-
set of the oomycetes are sterol
auxotrophs, consistent with previous reports which argue that
o
omycetes
belonging to the peronosporales
,

such as
Phytophthora

sp. cannot synthesise
their own sterols

(44)
.
F
ungi in anaerobic conditions or when the function of
pyridoxal 5'
-
phosphate synthase (EC
1.4.3.5) has been perturbed, also become
sterol auxotrophs and must

obtain
sterols

from the environment using a
transportation mechanism
(45)
. This HGT deriv
ed oomycete gene has a 3e
-
61
BLAST similarity score to the
vitamin

B6
p
yridoxal phosphate transporter of
Saccharomyces cerevisiae

(46)
. These
observations lead us to suggest
(tentatively) that this transporter may a
lso be used to scavenge
Pyridoxine

(pyridoxal or pyridoxamine) in order to obtain vitamin precursors and sterols in
addition

to transporting nucleobases as a source of nitrogen
.

19 (S1.19)

141189

(
P. sojae
)


Annotation by similarity search
(1
-
3)

suggests this HGT

candidate

encodes

an
extracellular protein with an

esterase/lipase domain. The functional role of
esterases and lipase enzymes is difficult to decipher based on homology
searches because substrate specifi
city often depends upon small changes in the
amino acid sequences and these enzyme families have relatively few functional
studies compared to the complexity of the protein families
(5, 6)
.
The

amino acid
sequence h
as strong sequence similarity to
carotenoid ester lipase enzymes of
the fungus
Pleurotus sapidus
which have been shown to perform
efficient
Y

hydrolysis of xanthophyll esters
(7)

and therefore important for processing

xanthophyll metabolites found in plant tissues.


This is one of
four separate transfers
of
esterase/lipase domain containing
extracellular proteins. It is difficult to predict the function of these proteins but
extracellular lipases have been shown to be

important pathogenic phenotypes
involved in the detection and breakdown of plant waxy cuticle
(10
-
12)

which may
represent an important metabolic resource for sterol and long chain fatty acids

for oomycete plant pat
hogens
.


20 (1.20)

EEY58144


Annotation suggests this HGT
candidate encodes

an extracellular protein
that is

a member of the
NPP1 like necrosis inducing protein also known as
necrosis and
ethylene
-
inducing peptide 1 (Nep1)
-
like proteins (NLPs). This pro
tein family is
found exclusively
in oomycetes, fungi and some bacteria. Infiltration of NPP1 into
leaves of
Arabidopsis thaliana

plants results in transcript accumulation of
pathogenesis
-
related genes, production of ROS and ethylene, callose
apposition, an
d hypersentative response (localized cell death in plant cells to
evade invasion)
(47)
. Furthermore,
NLPs trigger leaf necrosis that is genetically
distinct from immunity
-
associated programmed cell death and stimula
te
immunity
-
associated defenses. Hence, NLPs were proposed to have dual
functions in plant pathogen interactions, acting both as triggers of immun
ity

responses and as toxin
-
like virulence factors
(47)
.
NLP protein a
nalyses
revealed that identical structural properties were required to cause plasma
membrane permeabilization and cytolysis in plant cells, as well as to restore
bacterial virulence
(48)
. Interestingly, this protein

family
demonstrates
a
large
expansion in oomycetes genomes by gene duplication compared to fungi from
where th
e

gene family originate
d
.


Analysis of
P. infestans
microarray data
(27)

demonstrated that one gene fro
m
this HGT family showed significant up
-
regulation after five days
infection of plant
tissue (t
-
test
;

P value
at <0.01).

Y

21 (1.21)

EEY64154


Annotation suggests this
putative
HGT
candidate encodes

a c
onserved
hypothetical protein
with weak sequence simi
larity to
a
prokaryot
ic

a
ntibiotic
biosynthesis monooxygenase.

A
nalysis of
P. infestans
microarray data
(27)

demonstrated that one gene from this HGT family showed significant up
regulation after five d
ays infection

of plant tissue (t
-
test;

P value
at <0.01).

Y

22 (1.22)

EEY62062


Annotation by similarity search
(1
-
3)

suggest
s

this HGT is a
putative
pectate
lyase (
EC 4.2.2.2
).
Pectate lyase is known plant virulence factor
(49)

and is an
Y

enzyme involved in the maceration and soft rotting of plant tissue
. It
functions by
cleavage of (1
-
>4)
-
α
-
D
-
galacturonan polysaccharides to give oligosaccharides
with 4
-
deoxy
-
α
-
D
-
galact
-
4
-
enuronosyl groups at their non
-
reducing ends
(50)
.
Pectin is a major structural component of the plant cell wall and abundant source
of sugars in terrestrial

environments.


A
nalysis of
P. infestans
microarray data
(27)

demonstrated that one gene from
this HGT family showed significant up regulation after five days infection of plant
tissue
(t
-
test;

P value
at <0.05).

23 (1.23)

EEY67135

Yes (named
PcaH)

T
his HGT
candidate putatively encodes

an extracellular
intradiol dioxygenase.
These enzymes catalyze the critical ring
-
cleavage step in conversion of
catecholate derivatives (breaking the catechol C1
-
C2 bond


ring clea
vage) to
citric acid cycle intermediates. The family contains catechol 1,2
-
dioxygenases
and protocatechuate 3,4
-
dioxygenases
(EC
1.13.1.3)
and are predicted
to be
important in breakdown of aromatic compounds including lignin
(51)
.
Lignin is an
important structural molecule reinforcing plant tissues, is the

second most
abundant biopolymer
in nature
and is a significant source of aromatic groups in
natural environments.

Y

24 (1.24)

ABB22031


Annotation by similarity search
(1
-
3)

suggests this HGT
candidate encodes

an

extracellular
member of
endoglucanase family classified as glycosyl hydrolase
family 12,
formerly known as cellulase family H
(24)

and
responsible for
endohydrolysis of (1

4)
-
β
-
D
-
glucosidic linkages in cellulose, lichenin and cereal
β
-
D
-
glucans
. It
has been shown to be an import
ant enzyme in breakdown and
remodeling of
the
plant cell wall
(52)
.

Y

25 (1.25)

EEY67552


Annotation by similarity search
(1
-
3)

suggests this
HGT
candidate encodes

an
extracellular protein containing a
histidine phosphatase domain

found in

phytase
proteins.
The GenBank sequences with the highest sequence similarity and
which ha
s

been investigated with functional
experiments
is the phytase B family
of ascomycetes. Phytase

(inositol hexakisphosphate phosph
ohydrolase


E.C.
3.1.3.8) is capable of hydrolyzing phytic acid (
myo
-
inositol hexakisphosphate) as
well as other organophosphate substrates
(53)
.
Phytic acid (
myo
-
inositol
1,2,3,4,5,6
-
hexakis dihydrogen phosphate) is the primary storage form of
phosphate and inositol in plants and const
itutes 3

5% of the dry weight of seeds
in cereal grains and legumes
(54)
.
Phytases catalyze phosphate monoester
hydrolysis of phytic acid (
myo
-
inositol hexakisphosphate), which results in the
stepwise formation of
myo
-
inositol pentakis
-
, tetrakis
-
, tris
-
, bis
-
, and
monophosphates, as well as the libera
tion of inorganic phosphate
(55, 56)
.

Y


Analysis of
P. infestans
microarray data
(27)

demonstrated that one gene from
this HGT family showed significant up regulation after f
ive d
ays infection of plant
tissue (t
-
test;

P value
at <0.05).

26 (1.26)

EEY65395


This putative
HGT
candidate encodes

an extracellular endo
-
1,4
-

-
xylanase of
the glycosyl hydrolase family 10
,

formerly known as cellulase family F
(24)
.

The

enzyme is

an

endo
-

-
1, 4
-
xylanase (EC

3.2.1.8), which catalyzes the
endohydrolysis of 1,4
-

-
D
-
xylosidic linkages in xylan to short xylo
-
oligosaccharides of varying length
(24, 57)

from starch and hemicellulose
.
Hemicellulose is the second most abundant

natural polysaccharide

after
cellulose and is also an integral structural component of the plant cell wall.
Hemicellulose is made up of a number of different monomers with xylan as the
majority sugar.
Extracellular endo
-
1,4
-

-
xylanase
s

have been shown to
be
efficient degraders of plant derived xylan
(58)

suggesting that this enzyme family
is important
breakdown of

plant tissues.

Y

27 (1.27)

75147

(
P.ramorum
)


Our a
nnotation
suggests this
HGT encodes a member of Zin
c metalloprotease
proteins which include archaemetzincin
,

a
family of metalloproteases
characterized by a conserved motif (HEXXHXXGX
3
CX
4
CXMX
17
CXXC) that
contains an archetypal zinc
-
binding site and four Cys residues.

Enzymatic
assays performed with human r
ecombinant AMZs have demonstrated evidence
that these proteins are catalytically active metalloproteases that exhibit substrate
specificity and sensitivity to inhibitors and act predominantly as aminopeptidases
(59)
. Previous phylogenetic analysis
,

which
did

not include gene sampling from
the oomycetes
,

suggest
s

that HGT has played a role in the evolution of this gene
family
(59)
.

N

28 (1.28)

EEY56384


Annotation by similarit
y search
(1
-
3)

suggests this
HGT
candidate encodes

an
extracellular arabinogalactan endo
-
1,4
-
β
-
galactosidase (g
lycosyl hydrolase
family 53, GalA,
-

EC:3.2.1.89
). Enzymes from this protein family encode
endohydrolysi
s of (1

4)
-
β
-
D
-
galactosidic linkages in arabinogalactans

a
polymer of
arabinose

and
galactose

monosaccharides. Two classes of
arabinogalactans are f
ound in nature: plant arabinogalactan and microbial
arabinogalactan.
Pectin consists of “smooth” regions of α
-
1,4
-
linked galacturonic
acid and “hairy” regions of rhamnogalacturonan.
E
ndo
-
1,4
-

-
galactosidase
hydrolyze the galactan side chains that are part
of “hairy” region of pectin
(60,
61)
. Members of protein family has been linked to fungal pathogenesis of plants
(e.g.
(61)
).

Y

29 (1.29)

77558

(
P.ramorum
)


T
his HGT
putatively encodes

an aliphatic nitrilase (CN hydrolase family
-

EC
3.5.5.1
)
. N
itrilases belong to a

subfamily of the carbon
-
nitrogen hydrolase

enzyme superfamily and
catalyze the conversion of nitriles to the corresponding
carboxylic acids and ammonia, and are represents a highly diverse protein family
with many distinct sub
-
families discovered from unc
ultured microbes
(62)
.

Within
the protein family and with strong sequ
ence similarity to the oomycete

HGT
gene
s,

are the
cyanide hydratases
. These enzymes are

encoded by many plant
pathogenic fung
i and the acquisitio
n of thi
s

gene family

would
theoretically allow
oomycet
e
s to infect plants that synthesize

large amounts of defensive alkenyl
glucosinates, which break down into isothiocyanates and nitriles.

Isothiocyanates
and nitriles, including
hydrogen cyanide,
are of
ten present in plant tissues and
are toxic to fungi
(63)
. In the
ascomycete
plant pathogenic fungus
Leptosphaeria
maculans

t
his enzyme catalyses the breakdown of hydrogen cyanide to a less
toxic compound, formamide which can be used as
a
nitrogen source.

N

30 (1.30)

EEY68947


Annotation by similarity search
(1
-
3)

suggests thi
s HGT
candidate encodes

an
extracellular
α
-
L
-
rhamnosidase (EC 3.2.1.40


glycosyl hydrolase 78
(24)
). This
putative enzyme catalyses
hydrol
ysis of terminal non
-
reducing α
-
L
-
rhamnose
i.e.
hydrolyzing
α
-
1,2 and
α
-
1,6 linkages
(25, 26)
.
L
-
Rhamnose is an abundant
monosaccharide, a common constituent of glycolipids and glycosides, such as
plant pigments, pe
ctin, gums or biosurfactants.
Pectin from plant cell walls,
contains rhamnogalacturonan, consisting of rhamnose and galacturonate as the
main
-
chain and therefore this enzyme is important to many plant associated
fungi for modifying and/or degrading rhamnos
e
-
related compounds including the
plant cell wall
(25, 26)
. This represents a separate
extracellular
α
-
L
-
rhamnosidase

transfer to HGT

number 7

discussed
above
.


Y

31

76863

(
P.ramorum
)


Annotation suggests this HGT
encodes

an extracellular protein containing
sequence similarity to LysM domains. LysM domains are
found in a variety of
enzymes involved in b
acterial cell wall degradation and may have a general
peptidoglycan binding function
(64)
.
Recently, the first characterization of an
interaction of a LysM domain with its ligand was published and demonstrated
these protein domains binding of oligomers of
N
-
acetylglucosamine a
monosaccharide derivative of glucose that is a bui
lding block for bacterial
peptidoglycan and fungal chitin
(65)
.
During
Colletotrichum lindemuthianum
infection on bean
,

members of this protein family have been shown
to
accumulate in the walls of intracellular hyph
ae and the interfacial matrix, which
separates the hyphae from the invaginated host plasma membrane
(66)
. While in
Cladosporium fulvum
, the causal agent of
leaf mold of tomato,

this gene family
Y

has an expression pat
tern consistent with other secreted
C. fulvum
effector

proteins while RNAi knockdown experiments demonstrate
significant reduction in
growth of the fungus on host plants
(67)
.
LysM proteins are implicated in evasion

of chitin triggered plant immunity by fungal pathogens
(68)
.

The
data suggest
that thi
s HGT
may act as

an
effector.

32

EEY55495


Our annotations suggest that this HGT is an extracellular
conserved hypothetical
protein.

Y

33

134308

(
P.sojae
)


Annotation by similarity search
(1
-
3)

suggests this HGT

has strong similarity to a
fun
gal transcriptio
n factor
NmrA.
NmrA is a negative transcriptional regulator
involved in the post
-
translational modification controlling nitrogen metabolite
repression in fungi
(69)
.

Nm
r1 is implicated in fungal pathogenicity by its
interaction with fungal Tps1 in
Magnaporthe oryzae

(70)
.

N

34

EEY58177


Annotation by similarity search
(1
-
3)

suggests this HGT
encodes

a c
onserved
hypothetical protein
with sequence similarity to
Melampsora laricis
-
populin

and
Puccinia graminis

encoded proteins
.

Y



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