Preface

RNA interference (RNAi), a noble prize‐winning discovery made in the nematode, Caenorhabditis elegans , has been widely used in insect studies during the past 15 years. With its functionality in most eukaryotes, RNAi operates by downregulation of gene expression using double‐stranded RNA (dsRNA) intermediates in a cell. This evolutionary conserved post‐transcriptional gene silencing mechanism had been predominantly used as a powerful reverse genetic tool to understand insect gene functions at the beginning of the last decade. Until an Agriculture Biotech Company took a further step in exploiting RNAi technology for agricultural pest control by developing transgenic crop plants that can express dsRNA, thereby protecting the plants from herbivore attack. This breakthrough research created a lot of attention to RNAi technology as a potential next‐generation insect pest control method. Insect RNAi technology remains in the spotlight as evidenced by umpteen number of research/review articles, international symposia/meeting topics, and the birth of dozens of agri‐startup companies in recent years.

Though we have come a long way in using RNAi technology for insect control, there has not been a major breakthrough in the recent time, except for the cost‐efficient large‐scale production of dsRNA molecules. Because of its high specificity, RNAi offers great promise on pest control. However, RNAi efficiency depends on the sensitivity of insect orders, dsRNA treatment, or delivery methods, and these vary dramatically due to many factors. To exploit the full potential of this technology for insect pest control more research on the following topics are needed: (a) identification of potent target genes, (b) expansion of the technology to new or emerging insect pests, (c) better knowledge of RNAi mechanisms and efficiency across insect species, (d) development of suitable delivery platforms and formulations for improving stability, (e) effects on nontarget organisms, (f) safety and sustainability of this technology in the long run for insect pest control. With this in mind, we are presenting this special issue of Archives of Insect Biochemistry and Physiology on various aspects of RNAi research findings for insect control. It includes 10 diverse research articles from a pioneering insect RNAi research lab that could be of broader interest to the research community.

Rapidly expanding insect genomics and the availability of datasets publicly provide the opportunity to identify potential gene targets for RNAi. The choice of a target gene of interest is crucial for the success of RNAi in an insect species. Several considerations in the design of target gene like its abundance, tissue specificity, protein half‐life, noncross‐silencing, and more important, the ability to achieve a distinct phenotype are required for desirable RNAi efficiency. In this issue, Eid et al. studied the effect of E93, an ecdysone response transcription factor, on the female reproduction of red flour beetle. It is interesting to note that the orthologue of E93 in the fruit fly, Drosophila melanogaster , identified as a regulator of cell death, causes a decrease in vitellogenin synthesis and off‐spring production in the red flour beetle. In‐depth analyses on the inhibitor of apoptosis (IAP) genes and its potential as RNAi‐mediated control of red flour beetle, Tribolium castaneum was done by Yoon et al. This paper describes the need for studying the effects of different orthologues of the same gene as their RNAi efficiency differs. Besides red flour beetle, the IAP gene seems to work better as an RNAi target in non‐model but agriculturally important insect species, Colorado potato beetle, Leptinotarsa decemlineata . Maximo et al. evaluated four different RNAi target genes of interest and found that IAP and Actin combinatorial RNAi perform better than single RNAi effect in this beetle. These papers highlight screening of potential target genes, identifying and testing orthologues of the same gene, combinatorial RNAi effect, and conserved RNAi efficiency of the same gene in different insect species.

RNAi efficiency varies among insect orders and even within insect species of the same order. RNAi works well for control of coleopteran insects, but the outcome of RNAi response is variable in other insect orders. With new insect species are emerging as economically important pest and development of insecticide resistance is widespread in insects, it is critical to find alternate ways of control. In this special issue, six papers address this on agriculture, forestry, and storage pest belonging to Hemipteran, Coleopteran, and Lepidopteran insect orders. RNAi is quite challenging in Hemipteran insects, and stink bugs are emerging as notorious pests. A detailed understanding of RNAi mechanisms in these insects could help in developing a method of control. Research work by Gurusamy et al. outlines the obstacle of transport of orally derived dsRNA and the importance of the length of dsRNA in achieving the desired RNAi response in Southern Green Stinkbug, Nezara viridula . Howell et al. conducted a detailed study on RNAi response in cabbage Harlequin bug, Murgantia histrionica . Several RNAi targets and delivery methods were attempted, and it shows the promise of RNAi as a viable approach for managing this pest.

Asian long‐horned beetle, Anoplophora glabripennis , is a serious invasive forest pest hard to control. Studies by Kumar et al. showed that orally delivered dsRNA caused mortality in this beetle and RNAi could be used for its control. In another study, Koo et al. evaluated orthologues of red flour beetle genes as RNAi targets identified from cigarette beetle, Lasioderma serricorne transcriptome. Two of the five RNAi targets showed mortality by oral feeding of dsRNA. It is interesting to note that RNAi susceptibility is conserved in less evolved coleopteran insects from these studies and several RNAi delivery platforms can be developed for multiple coleopteran insect pests.

Lepidopteran insects are on the top of the list causing economic damage to crop plants and yet they are refractory to RNAi. Global expansion and damage caused by Fall armyworm (FAW) in recent years warrant alternate methods to control this notorious pest. Studies in the past have shown several factors attributing to poor RNAi efficiency in Lepidopteran insects and the need for developing carriers for dsRNA to achieve desire output in this order of insects. Similar to the studies in mosquito RNAi, Gurusamy et al. showed that Chitosan conjugated dsRNA promotes endosomal escape and improves RNAi efficacy in FAW, Spodoptera frugiperda . In another study, the same team showed the use of a lipid transfecting reagent to improve RNAi efficiency in FAW. It is promising to notice ways to improve RNAi response in refractory Lepidopteran insect species and, at the same time, a need for acceleration of research in this area. Not but not the least, a study by Chereddy et al. outlines the importance of evaluating the nontarget effects of RNAi that are critical for the commercialization of this technology for insect control.

Finally, I would like to thank all the reviewers for their timely review and comments that helped to improve the quality of research articles. I hope this special issue helps in furthering insect RNAi research to land on several milestones in the commercial application of this technology for insect control in the near future.

中文翻译：

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昆虫中的RNAi：Palli实验室的贡献。

前言

RNA干扰（RNAi）是在线虫秀丽隐杆线虫中获得的一项屡获殊荣的发现在过去的15年中已广泛用于昆虫研究。凭借其在大多数真核生物中的功能，RNAi通过在细胞中使用双链RNA（dsRNA）中间体下调基因表达来发挥作用。在过去的十年初期，这种进化保守的转录后基因沉默机制被主要用作了解昆虫基因功能的强大反向遗传工具。在农业生物技术公司采取进一步措施之前，通过开发可表达dsRNA的转基因农作物，从而利用RNAi技术控制农业害虫，从而保护植物免受草食动物的攻击。这项突破性的研究引起了人们对RNAi技术作为潜在的下一代害虫防治方法的广泛关注。

尽管我们在利用RNAi技术进行昆虫控制方面已经走了很长一段路，但除了具有成本效益的dsRNA分子大规模生产外，最近没有重大突破。由于其高特异性，RNAi为害虫防治提供了广阔前景。但是，RNAi效率取决于昆虫命令，dsRNA处理或递送方法的敏感性，并且由于许多因素，它们的差异很大。为了充分利用该技术在虫害防治方面的潜力，需要对以下主题进行更多研究：（a）鉴定有效的靶基因，（b）将技术扩展到新的或新兴的害虫，（c）更好地了解RNAi机制和昆虫种类的效率，（d）开发合适的递送平台和制剂以提高稳定性，（e）对非目标生物的影响，（f）从长远来看，该技术在控制虫害方面的安全性和可持续性。考虑到这一点，我们提出了本期特刊昆虫生物化学和生理学方面的文献，涉及有关昆虫防治的RNAi研究发现的各个方面。它包括来自一个开创性昆虫RNAi研究实验室的10篇不同研究文章，这些文章可能会引起研究界的广泛兴趣。

迅速扩展的昆虫基因组学和公开提供的数据集为确定RNAi潜在的基因靶标提供了机会。目的靶基因的选择对于昆虫中RNAi的成功至关重要。设计目标基因时需要考虑多个因素，例如其丰度，组织特异性，蛋白质半衰期，非交叉沉默，更重要的是，要获得理想的RNAi效率，需要具有独特的表型。在本期中，Eid等人。研究了蜕皮激素反应转录因子E93对红色甲虫雌性繁殖的影响。有趣的是，果蝇中的E93直向同源物是果蝇（Drosophila melanogaster）被认为是细胞死亡的调节剂，导致红色面粉甲虫中卵黄蛋白原合成的减少和后代的产生。在深入研究的细胞凋亡（IAP）基因的抑制剂和其作为赤拟谷盗的RNAi介导的控制电位分析，赤拟谷盗用Yoon等完成。本文描述了研究相同基因的不同直向同源物影响的需求，因为它们的RNAi效率不同。除了红粉甲虫，IAP基因在非模式但对农业有重要意义的昆虫物种（科罗拉多马铃薯甲虫，Leptinotarsa decemlineata）中作为RNAi靶标似乎更有效。Maximo等。我们评估了四种不同的感兴趣的RNAi靶基因，发现IAP和肌动蛋白组合RNAi在该甲虫中的表现优于单个RNAi效应。这些论文重点介绍了潜在靶基因的筛选，鉴定和测试同一基因的直向同源物，组合RNAi效应以及在不同昆虫物种中同一基因的保守RNAi效率。

RNAi效率在昆虫纲之间甚至在同一纲的昆虫物种内都不同。RNAi可以很好地控制鞘翅目昆虫，但是RNAi响应的结果在其他昆虫种群中是可变的。随着新的昆虫物种作为具有重要经济意义的害虫而出现，并且对昆虫的杀虫剂抗性发展十分普遍，寻找替代的控制方法至关重要。在本期特刊中，有六篇论文专门针对半球虫，鞘翅目和鳞翅目昆虫的农业，林业和储藏害虫。RNAi在半翅目昆虫中颇具挑战性，臭臭虫正逐渐成为臭名昭著的害虫。对这些昆虫中RNAi机制的详细了解可能有助于开发控制方法。Gurusamy等人的研究工作。内扎拉绿毛虫。Howell等。进行了关于白菜丑角臭虫（Murgantia histrionica） RNAi反应的详细研究。尝试了几种RNAi的靶标和传递方法，它显示了RNAi有望成为控制这种有害生物的可行方法。

亚洲长角甲虫Anoplophora glabripennis是一种严重的难以控制的入侵森林害虫。Kumar等人的研究。结果表明，口服递送的dsRNA导致该甲虫死亡，RNAi可用于控制它。在另一项研究中，Koo等人。我们评估了红色面粉甲虫基因的直向同源物作为从香烟甲虫Lasioderma serricorne转录组中鉴定出的RNAi靶标。五个RNAi靶标中的两个通过口服dsRNA表现出死亡率。有趣的是，根据这些研究，在进化较慢的鞘翅目昆虫中，RNAi的敏感性得以保留，并且可以为多种鞘翅目害虫开发几种RNAi传递平台。

鳞翅目昆虫排在首位，对农作物造成经济损失，但它们对RNAi不利。近年来，由秋天粘虫（FAW）引起的全球扩张和破坏为控制这种臭名昭著的害虫提供了替代方法。过去的研究表明，有几种因素可归因于鳞翅目昆虫的RNAi效率低下，以及需要开发dsRNA载体以按这种昆虫的顺序获得所需的产量。与对蚊子RNAi的研究相似，Gurusamy等人。结果表明，壳聚糖偶联的dsRNA促进了内体逃逸并提高了一汽小夜蛾（Spodoptera frugiperda）的RNAi功效。在另一项研究中，同一团队展示了使用脂质转染试剂来提高一汽中RNAi的效率。有望发现改善难治性鳞翅目昆虫物种中RNAi反应的方法，与此同时，需要加快这一领域的研究。同样重要的是，Chereddy等人的一项研究。概述了评估RNAi的非目标效应的重要性，这对于该技术用于昆虫控制的商业化至关重要。

最后，我要感谢所有评论者的及时评论和评论，这些评论和评论有助于提高研究文章的质量。我希望这个特别的问题有助于昆虫RNAi研究的进一步发展，并在不久的将来将该技术用于昆虫控制的商业应用中取得一些里程碑。