The oral secretions of insect herbivores are complex mixtures of organic and inorganic solutes and enzymes that are deposited onto plant tissues during the feeding process. Some specific components of insect oral secretions have been shown to confer important functions in mediating plant–insect interactions at the molecular level. In this review, we examined the biochemical studies of insect oral secretions to summarize the current knowledge of their compositions. We then moved beyond the functional studies of components of oral secretions, and focused on the literature that pinpointed specific molecular targets of these compounds. Finally, we highlighted the investigations of oral secretion components in the context of insect physiology, which shed light on the potential evolutionary trajectory of these multi-functional molecules.

Transient receptor potential (TRP) channels are a class of ion channel proteins that are closely related to thermosensation in insects. They are involved in detecting the ambient temperature and play vital roles in insect survival and reproduction. In this study, we identified and cloned two variants of the TRPA subfamily gene in Myzus persicae, MperTRPA1(A) and MperTRPA1(B), and analyzed their tissue expression by real-time quantitative PCR. Subsequently, these two variants of MperTRPA1 were expressed in the Xenopus oocyte system, and their functions were investigated using the two-electrode voltage clamp technique. The role of the MperTRPA1 gene in temperature adaptation of M. persicae was further determined by RNA interference and a behavioral choice assay to evaluate responses to temperature gradients. The results showed that the MperTRPA1 gene is widely expressed in tissues of M. persicae, with MperTRPA1(A) highly expressed in the mouthparts and MperTRPA1(B) mainly expressed in the antennae. The functional characterization results showed that both variants of MperTRPA1 could be activated and were not desensitized when the temperature increased from 20 to 45°C. The current value and thermal sensitivity (coefficient Q₁₀ value) of MperTRPA1(B) were significantly higher than those of MperTRPA1(A). When the MperTRPA1 gene was knocked down, the behavioral preference of M. persicae for the optimal temperature was reduced and tended to be at a higher temperature, showing a shift in the temperature adaptation range compared to both the wild type and dsGFP-treated M. persicae. In summary, our results elucidated the molecular mechanism of adaptive temperature perception in M. persicae mediated by the thermal sensor MperTRPA1.

Only few glufosinate-tolerant genes, such as phosphinothricin acetyltransferase (PAT) and bialaphos resistance (bar) identified from Streptomyces, are currently available for developing genetically modified rice in agricultural application. Following the rapid development of genome editing technology, generation of novel glufosinate-tolerant gene resources through artificial evolution of endogenous genes is more promising and highly desirable in rice molecular breeding program. In this study, the endogenous Glutamine synthetase1 (OsGS1) was artificially evolved by base-editing-mediated gene evolution (BEMGE) in rice cells to create novel alleles conferring glufosinate tolerance in rice germplasms. Two novel glufosinate-tolerant OsGS1 alleles (OsGS1-AVPS and OsGS1-+AF) and one reported tolerant allele (OsGS1-SGTA) were successfully identified from approximately 4200 independent hygromycin-tolerant calli. Germination assays and spray tests revealed that these three OsGS1 alleles confer glufosinate tolerance in rice. Furthermore, OsGS1-AVPS and OsGS1-SGTA were quickly deployed into the elite rice cultivar Nangeng 46 through precise base editing. Overall, our results demonstrate the feasibility of developing glufosinate-tolerant rice by editing an endogenous rice gene in molecular breeding programs.