Transgenic microRNA‐14 rice shows high resistance to rice stem borer

Abstract

Rice stem borer (RSB, Chilo suppressalis) is an insect pest that causes huge economic losses every year. Control efforts rely heavily on chemical insecticides, which leads to serious problems such as insecticide resistance, environment pollution, and food safety issues. Therefore, developing alternative pest control methods is an important task. Here, we identified an insect-specific microRNA, miR-14, in RSB, which was predicted to target Spook (Spo) and Ecdysone receptor (EcR) in the ecdysone signalling network. In-vitro dual luciferase assays using HEK293T cells confirmed the interactions of Csu-miR-14 with CsSpo and with CsEcR. Csu-miR-14 exhibited high levels of expression at the end of each larval instar stage, and its expression was negatively correlated with the expression of its two target genes. Overexpression of Csu-miR-14 at the third day of the fifth instar stage led to high mortality and developmental defects in RSB individuals. We produced 35 rice transformants to express miR-14 and found that three lines had a single copy with highly abundant miR-14 mature transcripts. Feeding bioassays using both T and T generations of transgenic miR-14 rice indicated that at least one line (C#24) showed high resistance to RSB. These results indicated that the approach of miRNAs as targets has potential for improving pest control methods. Moreover, using insect-specific miRNAs rather than protein-encoding genes for pest control may prove benign to non-insect species, and thus is worthy of further exploration.

RNA Interference in the Tobacco Hornworm, Manduca sexta, Using Plastid-Encoded Long Double-Stranded RNA

“…Previously, a study comparing the effectiveness of in vitro synthesized long dsRNA and an artificial microRNA (miRNA) targeting chitin synthase gene A in the brown planthopper revealed that long dsRNA was more effective in gene silencing, resulting in more significant effects on fecundity and ovary development compared to miRNA ( Li et al, 2017 ). Also, although several other studies using in planta expressed miRNA-based approaches showed positive results ( Agrawal et al, 2015 ; Jiang et al, 2017 ; He et al, 2019 ), complete plant resistance to insect herbivory was not accomplished in most cases. With regard to molecule sequence, the range of insect species affected by a single dsRNA product depends on the gene target.…”

miRNA-Mediated Interactions in and between Plants and Insects

“…The enzyme cytochrome P 450 307a1 (Cyp307a1) is involved in the biosynthesis of insect steroidal ecdysteroids that bind to the ecdysone receptor (EcR) to initiate and regulate the developmental process of molting [ 107 ]. In the rice stem borer, Chilo suppressalis , miR-14 post-transcriptionally targets the genes that encode both Cyp307a1 and EcR [ 108 ]. Rice plants that constitutively express miR-14 show enhanced resistance against the rice stem borer.…”

Contribution of Small RNA Pathway to Interactions of Rice with Pathogens and Insect Pests

“…Overexpression of Csu-miR-14 in RSB leads to abnormal development. Consistently, overexpression of Csu-miR-14 (OX-14) in rice leads to enhanced resistance to RSB (He et al 2019). Feeding RSB with OX-14 transgenic plants causes developmental defects and high mortality.…”