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BACKGROUND: The striped stem borer (SSB, Chilo suppressalis) is one of the most destructive insect pests on rice. As a chewing insect, SSB larval feeding causes a dramatic increase in rice defense responses. However, the effects of oral secretions (OSs) during SSB feeding on rice defense remain largely unexplored. RESULTS: In this study, based on transcriptome analysis results, treatment with SSB OSs regulated the expression of genes involved in the plant defense‐related pathways of calcium, mitogen‐activated protein kinases, reactive oxygen species, jasmonic acid (JA), herbivore‐induced plant volatiles (HIPVs), and protease inhibitors. Unsurprisingly, treatment with SSB OSs elicited the accumulation of JA and JA‐isoleucine in rice. The defense mechanisms activated by the cascade not only induced the expression of trypsin inhibitors, inhibiting the normal growth of SSB larvae but also induced HIPVs emission, rendering rice attractive to a common larval parasitoid. High‐throughput proteome sequencing of SSB OSs led to 534 proteins being identified and 343 proteins with two or more unique peptides being detected. CONCLUSION: The study demonstrates that SSB OSs trigger both direct and indirect defense mechanisms in rice, akin to the effects of SSB feeding. It identifies specific proteins in SSB OSs that may influence the interactions between SSB and rice during feeding, providing valuable insights for effectors research. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Damage caused by the rice striped stem borer (SSB), Chilo suppressalis (Walker) (Lepidoptera: Pyralidae), is much more severe on indica/xian rice than on japonica/geng rice (Oryza sativa) which matches pest outbreak data in cropping regions of China. The mechanistic basis of this difference among rice subspecies remains unclear. Using transcriptomic, metabolomic and genetic analyses in combination with insect bioassay experiments, we showed that japonica and indica rice utilise different defence responses to repel SSB, and that SSB exploited plant nutrition deficiencies in different ways in the subspecies. The more resistant japonica rice induced patterns of accumulation of methyl jasmonate (MeJA—part of a defensive pathway) and vitamin B1 (VB1—a nutrition pathway) distinct from indica cultivars. Using gene‐edited rice plants and SSB bioassays, we found that MeJA and VB1 jointly affected the performance of SSB by disrupting juvenile hormone levels. In addition, genetic variants of key biosynthesis genes in the MeJA and VB1 pathways (OsJMT and OsTH1, respectively) differed between japonica and indica rice and contributed to performance differences; in indica rice, SSB avoided the MeJA defence pathway and hijacked the VB1 nutrition‐related pathway to promote development. The findings highlight important genetic and mechanistic differences between rice subspecies affecting SSB damage which could be exploited in plant breeding for resistance. Summary Statement: This manuscript demonstrates that striped stem borer (SSB) avoided one defence pathway and hijacked another nutrition‐related pathway to promote development. The findings highlight important genetic and mechanistic differences between rice subspecies affecting SSB damage which could be exploited in plant breeding for resistance. [ABSTRACT FROM AUTHOR]

Fatty acid synthase (FAS) is a multifunctional enzyme that plays an important role in the formation of fatty acids. The fatty acids take part in many processes, such as cell signaling and energy metabolism, and in insects they are important in both cuticular hydrocarbon (CHC) formation and reproduction. Here we characterized the sequence structure and function of an FAS from the small brown planthopper (SBPH), Laodelphax striatellus. The full‐length open reading frame (ORF) sequence of LsFAS1 was 7122 bp, encoding a predicted protein of 2373 amino acid residues. There were 7 functional domains in the LsFAS1 protein sequence. Gene expression screening by real‐time quantitative polymerase chain reaction (RT‐qPCR) showed that LsFAS1 was expressed in all developmental stages. Relative expression was highest at the 4th‐instar and female adult stages. Among different tissues, the expression level of LsFAS1 in the ovary was the highest. Phylogenetic analysis showed that LsFAS1 clustered in a clade with 2 FASs from Nilaparvata lugens. Furthermore, these 3 FASs are related to cockroach BgFAS and locust LmFAS. After RNA interference‐mediated knock‐down, most treated insects died at eclosion. In addition, the lifespan of dsFAS1‐treated female adults was shorter than that of the dsGFP‐injected control, and offspring production decreased. Also, the expression of vitellogenin (Vg) and vitellogenin receptor (VgR) genes decreased. Virgin females dissected at days 2 and 4 post‐eclosion showed many matured oocytes in planthoppers treated with dsGFP but not with dsFAS1. These data highlight the importance of LsFAS1 in SBPH, including a role in reproduction. [ABSTRACT FROM AUTHOR]

Nine piggyBac-like elements (PLEs) were identified from the cotton aphid Aphis gossypii Glover. All the PLEs shared high sequence similarity with each other. However, eight of the nine PLEs were unlikely to encode functional transposase due to the existence of disruptive mutations within the coding regions. The other one PLE contained major characteristics of members in the piggyBac family, including TTAA target site duplications, inverted terminal repeats (ITRs), and an open reading frame (ORF) coding for a transposase with a putative DDD domain. This one with an intact transposase ORF was named AgoPLE1.1. The predicted transposase shared 47% similarity with that of Trichoplusia ni piggyBac IFP2. Phylogenetic analyses showed that AgoPLE1.1 was most related to the Heliothis virescens PLE1.1 ( HvPLE1.1) element, with 45% and 60% similarity at the nucleotide and amino acid levels, respectively. A functional assay demonstrated that AgoPLE1.1 encoded a functional transposase and was able to cause precise excision in cell cultures. On the other hand, few genomic insertion polymorphisms of AgoPLE1 were observed in the genome of the cotton aphid. These observations suggested that AgoPLE1.1 was a PLE that invaded the cotton aphid genome in recent periods and retained its activity. [ABSTRACT FROM AUTHOR]

N6‐methyladenosine (m6A) is the most prevalent modification in cellular RNA which orchestrates diverse physiological and pathological processes during stress response. However, the differential m6A modifications that cope with herbivore stress in resistant and susceptible crop varieties remain unclear. Here, we found that rice stem borer (RSB) larvae grew better on indica rice (e.g., MH63, IR64, Nanjing 11) than on japonica rice varieties (e.g., Nipponbare, Zhonghua 11, Xiushui 11). Then, transcriptome‐wide m6A profiling of representative resistant (Nipponbare) and susceptible (MH63) rice varieties were performed using a nanopore direct RNA sequencing approach, to reveal variety‐specific m6A modifications against RSB. Upon RSB infestation, m6A methylation occurred in actively expressed genes in Nipponbare and MH63, but the number of methylation sites decreased across rice chromosomes. Integrative analysis showed that m6A methylation levels were closely associated with transcriptional regulation. Genes involved in herbivorous resistance related to mitogen‐activated protein kinase, jasmonic acid (JA), and terpenoid biosynthesis pathways, as well as JA‐mediated trypsin protease inhibitors, were heavily methylated by m6A, and their expression was more pronounced in RSB‐infested Nipponbare than in RSB‐infested MH63, which may have contributed to RSB resistance in Nipponbare. Therefore, dynamics of m6A modifications act as the main regulatory strategy for expression of genes involved in plant–insect interactions, which is attributed to differential responses of resistant and susceptible rice varieties to RSB infestation. These findings could contribute to developing molecular breeding strategies for controlling herbivorous pests. [ABSTRACT FROM AUTHOR]