Caterpillar-Induced Rice Volatile (E)-β-Farnesene Impairs the Development and Survival of Chilo suppressalis Larvae by Disrupting Insect Hormone Balance

Abstract

Significant research progress has recently been made on establishing the roles of tps46 in rice defense. (E)-β-farnesene (Eβf) is a major product of tps46 activity but its physiological functions and potential mechanisms against Chilo suppressalis have not yet been clarified. In the present study, C. suppressalis larvae were artificially fed a diet containing 0.8 g/kg Eβf and the physiological performance of the larvae was evaluated. In response to Eβf treatment, the average 2nd instar duration significantly increased from 4.78 d to 6.31 d while that of the 3rd instar significantly increased from 5.70 d to 8.00 d compared with the control. There were no significant differences between the control and Eβf-fed 4th and 5th instars in terms of their durations. The mortalities of the 2nd and 3rd Eβf-fed instars were 21.00-fold and 6.39-fold higher, respectively, than that of the control. A comparative transcriptome analysis revealed that multiple differentially expressed genes are involved in insect hormone biosynthesis. An insect hormone assay on the 3rd instars disclosed that Eβf disrupted the balance between the juvenile hormone and ecdysteroid levels. Eβf treatment increased the juvenile hormones titers but not those of the ecdysteroids. The qPCR results were consistent with those of the RNA-Seq. The foregoing findings suggested that Eβf impairs development and survival in C. suppressalis larvae by disrupting their hormone balance. Moreover, Eβf altered the pathways associated with carbohydrate and xenobiotic metabolism as well as those related to cofactors and vitamins in C. suppressalis larvae. The discoveries of this study may contribute to the development and implementation of an integrated control system for C. suppressalis infestations in rice.

The main component of the aphid alarm pheromone (E)-β-farnesene affects the growth and development of Spodoptera exigua by mediating juvenile hormone-related genes

“…By overexpressing tps 46, eight kinds of metabolites were produced, and the dose ratio of these eight metabolites to the total metabolites was close to 1:10 4 ( Sun et al, 2017 ). Therefore, standard samples of the secondary metabolites were added to the artificial diet at a ratio of 1:10 4 to determine the effects of tps 46 metabolites on pests, such as C. suppressalis ( Yang et al, 2022 ) and S. exigua (pre-experiment of this study). Our results also indicated that 0.8 g/kg of EβF has a strong inhibitory effect on C. suppressalis larvae, at which concentration of EβF treatment was also reported that the larvae of C. suppressalis were almost all died and were unable to complete their life cycle ( Yang et al, 2022 ).…”

“…Because EβF and juvenile hormone are terpenes and have a similar structure ( Noriega, 2014 ; Li et al, 2021 ), EβF might affect the normal metabolism of juvenile hormone and disrupt the balance between juvenile hormone and ecdysone, which is essential for normal growth, metamorphosis, and reproduction, eventually causing the death of the S. exigua larvae ( Xu et al, 2021 ). EβF impairs the development and survival of C. suppressalis larvae by disrupting the normal metabolism of juvenile hormone and interfering with the normal hormone balance ( Yang et al, 2022 ). Based on the differential RNA-seq technique, the S. exigua juvenile hormone epoxide hydrolase-related genes (Unigene026066, Unigene025818, and Unigene025841) and the hormone ester-like enzyme-related genes (Unigene024849 and Unigene021363) were found to be significantly upregulated ( p < 0.05).…”

“…The EβF was added to the artificial diet of the larvae ( Yang et al, 2022 ). Based on our previous study ( Sun et al, 2017 ), the five concentration gradients of EβF (18794–84–8, Sigma-Aldrich), including 0.032, 0.16, 0.8, 4, and 20 g/kg (EβF/artificial diet, standard compound of EβF/uncured liquid feed), were set for initial testing.…”

“…Therefore, EβF and the TPSs associated with it might be applied as substitutes for chemical pesticides to protect plants. In our previous study, EβF showed a strong lethal effect on the larvae of the Chilo suppressalis , and consequently, C. suppressalis failed to complete its life cycle ( Yang et al, 2022 ). However, S. exigua could complete its life cycle when treated with the same concentration of EβF as used for controlling C. suppressalis .…”

Defence and nutrition synergistically contribute to the distinct tolerance of rice subspecies to the stem borer, Chilo suppressalis

“…Samples from five individual rice plants of the same treatment were pooled to form a biological replicate, and three replicates were collected for each treatment. RNA-seq analysis was performed as described previously (Yang et al, 2022) with minor modification. Library preparation and RNAseq were performed by Metware Biotechnology using an Illumina Hiseq platform and 125/150 bp paired-end reads were generated.…”