Biology Reference
In-Depth Information
that application of exogenous NO inhibits synthesis of a proteinase inhibitor
protein implicated in wounding in leaves (
Orozco-Cardenas & Ryan,
2002
). However, we are unaware of evidence for a role of the
C. fulvum
FHb in moderating NO availability in the plant.
In contrast to the obligate biotrophs, among the hemibiotrophs in Sup-
plementary Table S2 at
http://www.elsevierdirect.com/companions/
9780124076938
,
that is, those that have an initial biotrophic phase but kill
the host plant at a later stage of the association, are several that do contain
complete FHb sequences. A filamentous fungal FHb was first purified from
Fusarium oxysporum
(
Takaya, Suzuki, Matsuo, & Shoun, 1997
). This is a cos-
mopolitan species comprising both pathogenic and non-pathogenic isolates.
The pathogenic isolates of
F. oxysporum
cause wilt of several agricultural
crops; one of the economically more important and destructive forms is
the causal agent of fusarium wilt (Panama disease) of banana (
Musa s
pp.).
Several other examples can be seen in the Dothideomycetes, including
Dothistoma
spp.,
Mycosphaerella
spp. and
Septria musiva
. A variety of globins
are also found in
Phytophthora
spp., a hemibiotroph (Supplementary Table S1
at
http://www.elsevierdirect.com/companions/9780124076938
).
P. capsicis
is a pathogenic oomycete (water mold) infecting pepper plants. Oomycetes
are heterokonts (i.e. protists having two flagella of unequal length) whose
life cycle resembles that of the true fungi, with which they were formerly
classified. This relationship shows a high level of genetic diversity in host
resistance and pathogen avirulence proteins. Two varieties of pepper generate
NO as a defence and one variety is able to overcome the infection, apparently
correlated with the higher levels of NO detected (
Requena, Egea-Gilabert,
& Candela, 2005
). It is interesting, therefore, that
P. capsici
has several
globins—an SDgb, another missing the A helix, two FHbs and a TrHb3
(Supplementary Table S1 at
http://www.elsevierdirect.com/companions/
The necrotrophs, in contrast to the strict biotrophs, commonly contain
globin genes and FHb-encoding genes appear widespread, for example, in
the Glomerellales, such as
Colletotrichum
sp. and
Glomerella graminicola
(Supplementary Table S2 at
http://www.elsevierdirect.com/companions/
fungus that thrives in alkaline conditions and can be readily cultivated in
the laboratory. FHb genes are widespread in these sequences, as in the
sequences of Hypocreales, which are important plant pathogens.
B. cinerea
is a necrotrophic fungus with a broad host range. It colonizes not only senes-
cent tissues but also healthy plants and is presumably exposed to NO and
