Plants and animals alike fall sick
when infected by something pathogenic: viruses, bacteria, oomycetes, and more.
Thankfully, higher-order eukaryotes have evolved multiple ways to stop many of
these bugs from “taking over”. However, these mini critters don’t give up quite
so easily, and have a few clever tricks of their own to combat the host immune
system. This paper investigates the strategy of RNA silencing suppressors, a
counter defense utilized by the Phytophthora
microbial plant pathogens.
Before
discussing the paper, however, why bother to study this topic? First of all,
humans rely on plants for everyday life. If one understands the ways this group
of notorious crop pathogens causes plant sickness, we will have an edge in
curbing the economical and physical damage caused by these microbes to the
supply of food worldwide. For example, in Ireland, the potato famine was caused
by
Phytophthora infestans; since 1845, the pest causes endemic loss
of crop of up to 50% seven out of ten years (1). More importantly,
however, we will have a model that may be extrapolated to other critical plant
species and even animals when trying to tailor specific cures for diseases in
the future. As with all science, understanding a little piece of the puzzle has
multifaceted usefulness, because often this piece can help us solve the puzzles
in other plants and animals. This paper successfully characterizes factors in Phytophthora plant pathogens that
contribute to its successful virulence in the hopes of demonstrating that
further characterizations of factors in relevant organisms will help in finding
effective cures.
One method
by which a host may prevent, or at least lessen, the infection of pathogens,
especially against RNA viruses, is to encode for miRNAs or siRNAs; small-RNAs
that work to degrade the genetic material of the invading species (2). But what
happens when Phytophthora creates
something called an effector, a factor boosting virus fitness (3) where the
small-RNA defense mechanism is actually disabled? You get successful infection
of the invading species, or at least enhanced succeptibility. In a series of
clever experiments, Qiao et al. characterized PSR1 and PSR2, miRNA/siRNA
interfering proteins of pathogens belonging to the Phytophthora genus.
