Cassava is a starchy root crop for food and industrial applications in many countries around the world.
Among the factors that affect cassava production, diseases remain the major cause of yield loss. Cassava
anthracnose disease is caused by the fungus Colletotrichum gloeosporioides. Severe anthracnose attacks
can cause tip die-backs and stem cankers, which can affect the availability of planting materials especially
in large-scale production systems. Recent studies indicate that plants over- or under-express certain
microRNAs (miRNAs) to cope with various stresses. Understanding how a disease-resistant plant protects
itself from pathogens should help to uncover the role of miRNAs in the plant immune system. In this
study, the disease severity assay revealed different response to C. gloeosporioides infection in two cassava
cultivars. Quantitative RT-PCR analysis uncovered the differential expression of the two miRNAs and
their target genes in the two cassava cultivars that were subjected to fungal infection. The more resistant
cultivar revealed the up-regulation of miR160 and miR393, and consequently led to low transcript levels in
their targets, ARF10 and TIR1, respectively. The more susceptible cultivar exhibited the opposite pattern.
The cis-regulatory elements relevant to defense and stress responsiveness, fungal elicitor responsiveness
and hormonal responses were the most prevalent present in the miRNAs gene promoter regions. The
possible dual role of these specific miRNAs and their target genes associated with cassava responses to
C. gloeosporioides is discussed. This is the first study to address the molecular events by which miRNAs
which might play a role in fungal-infected cassava. A better understanding of the functions of miRNAs
target genes should greatly increase our knowledge of the mechanism underlying susceptibility and lead
to new strategies to enhance disease tolerance in this economically important crop.