Regulation of host plant defenses against pathogens and herbivores by
miRNA: Balancing resistance and productivity trade-offs
Abstract
Rice (Oryza sativa L.) is continuously challenged by various biotic
stresses including fungal, bacterial, viral, parasites, and insect
pests. These stresses threaten global rice productivity each year.
Numerous resistance (R) genes have been identified, but only a few of
them have been deployed in rice improvement programs due to the rapid
breakdown of resistance, pleiotropic effects, and negative associations
with important agronomic traits. Modern varieties are being developed by
pyramiding multiple R-genes from diverse germplasm. However, unregulated
expression of R-genes often comes with unexpected yield trade-offs and
poor plant fitness. MicroRNAs (miRNAs) are endogenous, short,
single-stranded, non-coding RNA molecules that function as master
regulators for balancing immunity and yield. Defense-related miRNAs such
as Osa-miR156, Osa-miR162, Osa-miR396, and Osa-miR1873 have been
identified in rice that fine-tunes immunity and yield under various
biotic stresses. Recent advances showed that many immune-responsive
miRNAs also regulate many complex traits of agronomic importance. This
allows researchers to assemble the appropriate combinations of
agriculturally important traits to be targeted using genetic engineering
approaches that involved miRNAs.