Insect Pheromone Biochemistry and Molecular Biology

Gary Blomquist, Richard Vogt

• Publisher: Academic Press
• Year: 2020
• eBook ISBN: 9780128196298
• Edition: 2
• Topic: Biological Sciences
• Subtopic: Biochemistry
• Index: Biological Sciences

Insect Pheromone Biochemistry and Molecular Biology, Second Edition, provides an updated and comprehensive review of the biochemistry and molecular biology of insect pheromone biosynthesis and reception. The book ties together historical information with recent discoveries, provides the reader with the current state of the field, and suggests where future research is headed. Written by international experts, many of whom pioneered studies on insect pheromone production and reception, this release updates the 2003 first edition with an emphasis on recent advances in the field. This book will be an important resource for entomologists and molecular biologists studying all areas of insect communication.- Offers a historical and contemporary perspective, with a focus on advances over the last 15 years- Discusses the molecular and regulatory mechanisms underlying pheromone production/detection, as well as the evolution of these processes across the insects- Led by editors with broad expertise in the metabolic pathways of pheromone production and the biochemical and genetic processes of pheromone detection

1

Production and reception of insect pheromones – Introduction and overview

Gary J. Blomquist¹ and Richard G. Vogt², ¹1Department of Biochemistry and Molecular Biology, University of Nevada, Reno, NV, United States, ²2Department of Biological Sciences, University of South Carolina, Columbia, SC, United States

Abstract

Pheromone regulate and the behavior, physiology and development of insects. Since Butenandt and colleagues identified the Bombyx mori sex attractant pheromone bombykol in 1959, considerable research has focused on the identification of pheromones across the insects, and how these molecules are synthesized by one sex and detected by the other. Advances in research have often been driven by advances in technology. The previous edition of this book appeared shortly after the first successfully sequencing of an insect genome, that of the fly Drosophila melanogaster; this, and the subsequently increased availability of insect genomic sequences, allowed for rapid identification of chemosensory relevant genes and gene products and the resulting characterizations using traditional and novel techniques. This chapter provides an introduction to the book’s chapters, which were written by experts working at the frontiers of pheromone physiology, biochemistry and molecular biology.

Keywords

Pheromone production; Biosynthesis; Reception; Detection

1.1 Introduction

While insects make use of many chemical cues to assess their environment, pheromones have profound roles in the regulation of behavior throughout this most numerous animal phylum. Karlson and Luscher (1959) proposed the term ‘pheromone’ as “substances which are secreted to the outside by an individual and received by a second individual, in which they release a specific reaction”. In that same year, the chemical structure of the first insect pheromone, bombykol (E, Z)-10,12-hexadecadien-1-ol, from the silkworm moth was elucidated (Butenandt et al., 1959). This first identified pheromone was a sex attractant, but since then, semiochemicals have been shown to serve in a variety of behavioral roles, including sex attraction, aggregation, caste recognition, species recognition, dispersal (spacing or epidiectic), alarm, recruitment (trail), task specific cues and colony integrity (group odor). Since 1959, pheromone molecules have been identified for well over 3000 insect species. And throughout this period, there has been keen interest in how these molecules are synthesized and their synthesis and release regulated, and how these molecules are detected and subsequently modify behavior. This book focuses on these processes, and especially on research that has occurred since the previous edition was (Vogt, 2003), research which has been dominated by advances in nucleotide and genome sequencing and gene manipulation.

This book is organized into two sections: (1) the production of pheromones, primarily in female insects, and (2) the reception of pheromones, primarily in males. While the focus is on recent work, earlier work is mentioned for the sake of context and completeness. Clearly the field has undergone tremendous advances in the last three plus decades. The tools used to understand biochemical processes in pheromone production and reception have mirrored the rapid advances made in how we study biological processes, and the application of molecular and genomic techniques has allowed new and more in depth understanding of the processes of how insects produce and receive chemical signals. Our understanding of pheromone production has evolved from identifying the pheromone biosynthetic pathways in a few insects in 1987 to where, in some cases, essentially all of the genes involved in coding for the enzymes to produce some pheromones are now known. Indeed, it is now possible to import the genes used to make insect pheromones into yeasts and plants and obtain products that can be used to attract insects (Ding et al., 2014) (Chapter 3). And while the basic players of pheromone detection were known in 2003, including the full genomic repertoire known for one insect, Drosophila melanogaster, subsequent research utilizing gene manipulation techniques has greatly enhanced our understanding of the underlying molecular mechanisms and interactions, and genomic sequences of multiple species has increased our understanding of the evolutionary depth of these processes.

1.2 Pheromone production

After Butenandt et al. (1959) identified the first insect pheromone, the chemical identity of the pheromones of thousands of insect species have been determined, and most are comprised of two or more related molecules. Certain insect groups use closely related structures as their pheromones, and they produce the unique pheromone blends by modifying the products of normal metabolism with pheromone gland specific enzymes to produce the myriad of pheromone molecules. Because of their economic impact, lepidopterans have received more attention than any other Order regarding pheromone production.

Lepidopterans often use highly specific desaturases, chain shortening of fatty acids along with specific modifications of the functional group to produce the alcohols, aldehydes, esters and hydrocarbons that comprise many of their pheromones, and this is covered in depth in Chapter 2. Transcriptomic studies of the pheromone glands of a number of insects are available, which has led in some cases to their cloning and functional expression.

Many lepidopterans use a pheromone biosynthesis activating neuropeptide (PBAN) that regulates pheromone production by activating specific enzymes required for pheromone biosynthesis. At the time of publication of the first edition of this book (2003), the PBAN receptor was being cloned and functionally expressed from Heliothis zea by the Jurenka lab (Choi et al., 2003) and from Bombyx mori (Hull et al., 2004). There is a high degree of sequence similarity among the PBAN receptors studied to date, and the signal transduction leading to increased pheromone production has been determined in a few cases (Chapter 2). Other insect groups use the same hormone that controls vitellogenesis and egg development, juvenile hormone, to induce pheromone production, thus coordinating mating and egg production.

The depth of our understanding of pheromone production in lepidopterans is illustrated in Chapter 3, where some of the unique genes of lepidopteran pheromone production have been incorporated into plants and yeast in order to produce specific pheromone components.

Some beetle species have evolved specific enzymes to modify the products of the isoprenoid pathway to produce monoterpenoid pheromone products and this is reviewed in Chapter 4. Among bark beetles, the long-standing question of whether they use host tree precursors or synthesize the carbon skeleton of aggregation pheromones de novo has been more completely answered, with the answer different in different species. The Dendroctonus genera appear to use host tree precursors extensively, especially α-pinene, which they modify to produce some pheromone components. Very recent studies show that female D. ponderosae hydroxylate host tree derived α-pinene to form trans-verbenol throughout development and then store trans-verbenol as esters of fatty acids. The females then release trans-verbenol as they enter a new host tree where it is part of the aggregation pheromone that leads to the mass attacks that overcome a tree’s defenses (Chiu et al., 2018). Those Dendroctonus species that use frontalin and exo-brevicomin synthesize these pheromone components de novo, with frontalin arising from the terpenoid pathway and exo-brevicomin from a fatty acid pathway. The Ips genera have evolved the enzymes to produce the monoterpenoid pheromones ipdienol and ipsenol de novo and it appears that very little of these aggregation pheromones arise from host tree precursors. An RNA-seq study in Ips confusus showed that all of the gene products involved in ipsenol production are upregulated 30–2000-fold, and the pheromone specific enzymes have been expressed and assayed (Fisher, MacLean, Tittiger and Blomquist, unpublished data) (Chapter 4).

In the model organism Drosophila melanogaster a number of very powerful molecular genetic tools have been applied to the study of pheromone production. Chapter 5 describes these studies which have answered some fundamental questions and confirmed the complexity of pheromone production and its regulation in this species.

The honey bee represents a highly complex social and reproductive organization which is regulated by signals from the mandibular, tergal and Dufour’s gland. The production and regulation of these signals is reviewed in Chapter 6.

Many insect species use specific hydrocarbon components in chemical communication, and these arise from specific fatty acid synthases, desaturases, elongases, fatty acyl-CoA reductases and a novel cytochrome P450 that has both alcohol oxidase and aldehyde decarbonylase activity (Chapter 7). At the time the first edition of this book was published (2003), none of the genes involved in hydrocarbon production were known. In the last decade many of the specific genes involved in producing the fatty acid precursors, elongation reactions, fatty acyl-CoA reductases and final steps catalyzed by a unique cytochrome P450 (CYP4G) that is an alcohol oxidase/aldehyde decarbonylase have been identified, and in some cases expressed and assayed (Qiu et al., 2012; MacLean et al., 2018). Many different groups of insects use hydrocarbons in chemical communication, and this chapter does not concentrate on a specific group of insects, but brings studies from many species together to better understand hydrocarbon pheromone production.

The Nasonia have become a frequently used model for the study of parasitoid wasp biology. Males produce fatty acid derived chiral lactones that arrest and attract virgin females. These lactones are derived from de novo produced fatty acids that undergo specific desaturation, epoxidation, chain shortening, lactone formation and then epimerization, with many of the steps characterized (Chapter 8).

Very recent work demonstrated that stink bugs bios...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• List of contributors
• Acknowledgments
• 1. Production and reception of insect pheromones – Introduction and overview
• 2. Lepidoptera: Female sex pheromone biosynthesis and its hormonal regulation
• 3. Biological production of insect pheromones in cell and plant factories
• 4. Pheromone production in bark beetles
• 5. Drosophila pheromone production
• 6. Pheromone communication in honey bees (Apis mellifera)
• 7. Hydrocarbon pheromone production in insects
• 8. Pheromone biosynthesis in Nasonia
• 9. Biosynthesis of terpene pheromones in hemiptera/stink bugs
• 10. The neuroethology of labeled lines in insect olfactory systems
• 11. Pheromone detection and processing in the silkmoth Bombyx mori
• 12. Molecular mechanisms of pheromone detection
• 13. Insect odorant receptors: Function and regulation
• 14. Multiscale timing of pheromone transduction in hawkmoth olfactory receptor neurons
• 15. Olfactory genomics within the Lepidoptera
• 16. Olfactory genomics of eusociality within the Hymenoptera
• 17. Olfactory genomics of the Coleoptera
• 18. Mechanism and dynamics of insect odorant-binding proteins
• 19. Odor degrading enzymes and signal termination
• 20. Olfactory genomics and biotechnology in insect control
• 21. Reflections on antennal proteins: The evolution of pheromone binding proteins; diversity of pheromone degrading enzymes; and the distribution and behavioral roles of SNMPs
• Index