Flavonoids are known to contribute to plant defense against herbivorous insects in a variety of systems, but their specific role in cassava (Manihot esculenta) resistance to the cassava mealybug (Phenacoccus manihoti) has remained unclear. Through expression profiling of nine flavonoid biosynthesis genes in high-resistance and high-susceptibility cassava varieties, chalcone synthase (CHS) was identified as the most differentially expressed candidate. Virus-induced gene silencing (VIGS) of CHS in the high-resistance variety C1115 led to a 67.5% reduction in CHS transcript levels, a 60.6% decrease in enzyme content, and a 29.7% decline in total flavonoid content. This was accompanied by the suppressed expression of downstream genes CHI and LAR. Silenced plants showed increased leaf damage and a higher pest index, effectively rendering the resistant phenotype susceptible. Furthermore, mealybugs feeding on these plants exhibited a 1.3-fold increase in their net reproductive rate. These results indicate that CHS-dependent flavonoid accumulation is one of the components required for resistance to P. manihoti in the high-resistance variety C1115, and identify CHS as a promising candidate target for marker-assisted breeding.

MicroRNAs (miRNAs) are a class of small non-coding RNAs, which function as regulators of gene expression and contribute in numerous physiological processes. However, little is known referring to miRNAs function in insect chemosensation. In the current study, nine small RNA libraries were constructed and sequenced from the antennae of nymphs, adult males and females of Apolygus lucorum. In total, 399 miRNAs were identified including 275 known and 124 novel miRNAs. Known miRNAs were classified into 71 families, amongst which, 23 families were insect-specific. Expression profile analysis showed that miR-7-5p_1 was the most abundant miRNAs in the antennae of A. lucorum. Altogether, 69708 target genes related to biogenesis, membrane and binding activities were predicted for 399 miRNAs. Particularly, 15 miRNAs were found to target 16 olfactory genes. These miRNAs could be involved in regulation of olfactory-associated genes ex-pression. Comparing the antennae of nymphs, adult males and females, 94 miRNAs were found to be differentially expressed. The expression levels of some differentially expressed miRNAs measured by qPCR were consistent with sequencing results. This study provides a global miRNAs transcriptome in the antennae of A. lucorum and valuable information for further investigation on miRNA-mRNA interactions, especially the functions of miRNAs in regulating chemosensation.