Table 20.2 (continued)
Genes involved in endosymbiosis and function Implications and findings
leguminosarum biovar viciae 3841 on the root
hairs
– Hsero_1294 and fhaB: Filamentous
hemagglutinin proteins.
In Triticum aestivum, upregulation of two
genes of Hsero_1294 and fhaB of
H. seropedicae SmR1 suggests involvement of
root attachment.
Lipopolysaccharide, membrane proteins
– rfbB (Hsero_4410): dTDP-D-glucose
4,6-dehydratase, biosynthesis of rhamnose.
In Zea mays, 100-fold lower attachment to root
surface, reduced efficiency in endophytic colonization of H. seropedicae SmR1
– rfbC (Hsero_4411): dTDP-4-keto-6deoxy-D-glucose 3,5-epimeras, biosynthesis of
rhamnose.
In Z. mays, 100-fold lower attachment to root
surface, reduced efficacy in endophytic colonization of H. seropedicae SmR1
– ampG (YP_003773531.1): Muropeptide
permease of the major facilitator superfamily,
recycling of the cell wall peptidoglycan.
In Z. mays, ten-fold reduction in endophytic
population in roots at one and 3 days after
inoculation of H. seropedicae SmR1
Detoxification
Endophyte survival requires the ability to
detoxify or manage movement of xenobiotics
using efflux pumps. G. diazotrophicus has
poor survival in the rhizosphere (Saravanan
et al. 2008; Baladani and Baldani 2005; Matiru
and Thomson 1998).
– gor (GDI_2216): Glutathione reductase
(EC 1.8.1.7)
Reduction in number of tightly root-associated
endophytic colonization of G. diazotrophicus
PAL5 in O. sativa subsp. Indica cv. IR42
(Alqueres et al. 2013)
– sodB (GDI_2168): SOD
Reduction of number of tightly root-associated
endophytic colonization of G. diazotrophicus
PAL5 in O. sativa subsp. Indica cv. IR42
(Alqueres et al. 2013)
– smeE (SMD_3657): RND efflux system,
inner membrane transporter, part of the
SmeDEF efflux pump involved in quinolone
resistance
Impaired colonization of roots of
Stenotrophomonas maltophilia D457 in Brassica napus cv. Californium (Garcia-Leon et al.
2014)
Fe uptake
– Dicitrate ton-B dependent receptors
– Siderophore biosynthesis
Biologically available Fe is limited in plants
and endophytes. Uptake of ferric siderophore
complexes is achieved via TonB dependent
receptors (Galperin 2005). Endophytes with
large numbers of these receptors may compete
with plants or fungi for iron acquisition (Miter
et al. 2013)
Degradation of organic compounds
G. diazotrophicus is at the extreme low end of
the ability to degrade complex plant metabolites (Dent 2018).
– alkB (Bphyt_5401): Alkane
monooxygenase
– alkane hydroxylase (Bphyt_1856)
– dioxygenases
In Burkhoderia phytofirmans PsJN, alkane
monooxygenase (alkB, Bphyt_5401) and
cytochrome P450 alkane hydroxylase
(Bphyt_1856). AlkB enzymes are required for
break-down of aliphatic hydrocarbons.
(continued)
20 The Diazotroph as an Endophyte and How a Diazotroph Interacts with Its. . .
397
Genes involved in endosymbiosis and function Implications and findings
leguminosarum biovar viciae 3841 on the root
hairs
– Hsero_1294 and fhaB: Filamentous
hemagglutinin proteins.
In Triticum aestivum, upregulation of two
genes of Hsero_1294 and fhaB of
H. seropedicae SmR1 suggests involvement of
root attachment.
Lipopolysaccharide, membrane proteins
– rfbB (Hsero_4410): dTDP-D-glucose
4,6-dehydratase, biosynthesis of rhamnose.
In Zea mays, 100-fold lower attachment to root
surface, reduced efficiency in endophytic colonization of H. seropedicae SmR1
– rfbC (Hsero_4411): dTDP-4-keto-6deoxy-D-glucose 3,5-epimeras, biosynthesis of
rhamnose.
In Z. mays, 100-fold lower attachment to root
surface, reduced efficacy in endophytic colonization of H. seropedicae SmR1
– ampG (YP_003773531.1): Muropeptide
permease of the major facilitator superfamily,
recycling of the cell wall peptidoglycan.
In Z. mays, ten-fold reduction in endophytic
population in roots at one and 3 days after
inoculation of H. seropedicae SmR1
Detoxification
Endophyte survival requires the ability to
detoxify or manage movement of xenobiotics
using efflux pumps. G. diazotrophicus has
poor survival in the rhizosphere (Saravanan
et al. 2008; Baladani and Baldani 2005; Matiru
and Thomson 1998).
– gor (GDI_2216): Glutathione reductase
(EC 1.8.1.7)
Reduction in number of tightly root-associated
endophytic colonization of G. diazotrophicus
PAL5 in O. sativa subsp. Indica cv. IR42
(Alqueres et al. 2013)
– sodB (GDI_2168): SOD
Reduction of number of tightly root-associated
endophytic colonization of G. diazotrophicus
PAL5 in O. sativa subsp. Indica cv. IR42
(Alqueres et al. 2013)
– smeE (SMD_3657): RND efflux system,
inner membrane transporter, part of the
SmeDEF efflux pump involved in quinolone
resistance
Impaired colonization of roots of
Stenotrophomonas maltophilia D457 in Brassica napus cv. Californium (Garcia-Leon et al.
2014)
Fe uptake
– Dicitrate ton-B dependent receptors
– Siderophore biosynthesis
Biologically available Fe is limited in plants
and endophytes. Uptake of ferric siderophore
complexes is achieved via TonB dependent
receptors (Galperin 2005). Endophytes with
large numbers of these receptors may compete
with plants or fungi for iron acquisition (Miter
et al. 2013)
Degradation of organic compounds
G. diazotrophicus is at the extreme low end of
the ability to degrade complex plant metabolites (Dent 2018).
– alkB (Bphyt_5401): Alkane
monooxygenase
– alkane hydroxylase (Bphyt_1856)
– dioxygenases
In Burkhoderia phytofirmans PsJN, alkane
monooxygenase (alkB, Bphyt_5401) and
cytochrome P450 alkane hydroxylase
(Bphyt_1856). AlkB enzymes are required for
break-down of aliphatic hydrocarbons.
(continued)
20 The Diazotroph as an Endophyte and How a Diazotroph Interacts with Its. . .
397