Page 15 - Volume 5, Issue 2, July 2012

Phytobacterial type III secretion systems in the era of biotechnology

43

cially among distant plant families, some of

which are highlighted in Table 1. This might

reveal new potential in genetic engineering

towards phytoprotection, as exploitation of

a certain effector function in a specific crop

could lead to priming of defense respons-

es upon challenge with a pathogen. More-

over, the genomics era for plant pathogens,

which began with the sequencing of

Xylella

fastidiosa

genome in year 2000 (Simpson

et

al.

, 2000) and the new comparative analysis

of genomes (Hamilton

et al.

, 2011), which al-

lows for identification of conserved and di-

vergent features, thus leading to species,

pathovar and isolate-specific genes, sup-

ports diagnostics research towards new

molecular kits based on such targets, where

both

hrp

genes and T3SS effectors might be

in the centerfold.

With regard to applications, it is per-

haps significant that various uses of bacte-

rial effectors have been the subject of sev-

eral patents, to enable possible applications

in a number of areas, including plant disease

and pest control. In addition, new frontier

areas are likely to emerge from the develop-

ments in high-throughput DNA sequencing

(next-generation sequencing technologies).

Very high-throughput DNA sequencing

platforms are commercially available at af-

fordable costs and new more cost effective

techniques are under development. Rapid

genome-wide characterization and targeted

capture of genomic subsets and polymor-

phisms from many phytopathogen strains

at a time, and public access to genome, tran-

scriptome and metagenome data will likely

reshape many areas of “phytopathogenics”

and will enable applications in disease di-

agnosis, epidemiology, effectoromics and

comparative pathogenomics and the de-

velopment of resistance strategies in the fu-

ture. Characteristic of this trend are two re-

cent publications (Baltrus

et al.,

2012; Bart

et

al.,

2012), which concern the sequencing of

new 14 and 65 phytobacterial genomes, re-

spectively.

Research on antibacterial compounds

for phytoprotection could follow the mam-

malian research initiatives. Specificity of

T3SS virulence inhibitors could render field

application feasible, in contrast to conven-

tional antibiotics. However, development of

such molecules would face drawbacks sim-

ilar to those of the mammalian pathogens:

post-infection usage, broad range activi-

ty, targeting of infected tissue and non-tar-

get organism safety issues. In addition, the

lack of an adaptive immune system would

render T3SS therapeutics more complicat-

ed and disqualify methods such as usage of

secreted effectors as vaccines and T3SS mu-

tants as live vaccines, which are under inves-

tigation for mammalian bacterial pathogens

(see Coburn

et al.

, 2007).

Disclaimer:

Mention of commercial product

or manufacturer does not imply endorse-

ment by the authors

.

Literature cited

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