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Little is known about the process of sex determination at the molecular level in species belonging to the subclass Acari, a taxon of arachnids that contains mites and ticks. The recent sequencing of the transcriptome and genome of the western orchard predatory mite Metaseiulus occidentalis allows investigation of molecular mechanisms underlying the biological processes of sex determination in this predator of phytophagous pest mites. We identified four doublesex-and-mab-3-related transcription factor (dmrt) genes, one transformer-2 gene, one intersex gene, and two fruitless-like genes in M. occidentalis. Phylogenetic analyses were conducted to infer the molecular relationships to sequences from species of arthropods, including insects, crustaceans, acarines, and a centipede, using available genomic data. Comparative analyses revealed high sequence identity within functional domains and confirmed that the architecture for certain sex-determination genes is conserved in arthropods. This study provides a framework for identifying potential target genes that could be implicated in the process of sex determination in M. occidentalis and provides insight into the conservation and change of the molecular components of sex determination in arthropods.

AN APPRECIATION OF WHATmolecular biology can do for studies of insects has been slow in coming to many parts of the entomological community. I vividly recall the day a few years ago when an entomologist friend said tome: “You know,Dave, I Þnally understand how molecular biology can help us to answer some questions that we just couldnOt answer before.” The book Insect Molecular Genetics (2nd edition) by Marjorie Hoy represents a step in the right direction toward hearing this kind of statement more often. Having said that, I will add that there is room for improvement here along some of the lines described below. However, none of this should be construed as taking away frommy appreciation of the scale of the effort involved in writing this kind of book, and the help it will provide in bridging these two very diverse disciplines. This is the second edition of this book, and it is interesting to note that neither of the two other Molecular Entomology type books (Molecular Approaches to Fundamental and Applied Entomology, edited by J. Oakeshott and M. J. Whitten, and Insect Molecular Science, edited by J. Crampton and P. Eggleston) that came out about the same time as HoyOs Þrst edition has been revised for a second edition. The book is described as both a textbook for a course in Molecular Genetics/Entomology and as a source book for entomologists beginning their research careers with no background in molecular biology. Much of the material is drawn from the vast array of literature on Drosophila melanogaster. This is understandable, of course, because of the central role that this organism has had in the history of genetics, but in many cases the emphasis on Drosophila is overdone. In strictly molecular terms, the work on economically important insects such as the mosquito Anopheles gambiae and the silkmoth Bombyx moryi may soon equal or surpass this body of knowledge. The Þrst part entitled “Genes and genome organization in eukaryotes” begins with material (Chapters 1 and 2) that can be found in virtually any contemporary textbook on Genetics. Chapters 3 and 4 in this section begin the task of focusing more directly on what is known about insect genes and genomes. Part II is on techniques in molecular genetics, and here again much of this material is like that found in any number of other books currently available. Chapters 5-8 in this section deal with general molecular techniques, and it is only in Chapter 9 that the focus shifts to insect-speciÞc material. This chapter is entitled “Transposable-element vectors to transformDrosophila and other insects,” and the nature of this chapter resects some of both the strengths and weaknesses of this book. Almost two-thirds of this chapter is devoted to a review of the P-element system of transformation in Drosophila. This might be of interest as a system to introduce the concept of gene transfer in eukaryotes, but it will not be useful tomost entomologists actually trying to do this kind of work. Despite intensive efforts, it has been abundantly clear for some time now that P-elements are not going to be useful for insects outside of this genus (Handler et al. 1998). The latter part of this chapter does, however, do a good job of introducing some of the vectors such as piggyBac, Hermes, and Minos that are useful in the transformation of other insects and should be of interest to entomologists. However, here I was disappointed in the lack of information aboutmarkers to be used to detect transformation events. As the book points out, these transformation methods are still relatively inefÞcient, and for this reasongoodmarkers areessential. Theone section dealing with “How are transformed insects identiÞed” (section 14.10) is less than one page long, and gives only scant mention of markers such as GFP that have for some time now (see, for example, Pinkerton et al. 2000) played a key role in the ability to transform a wide range of insects. The third part of the book deals more speciÞcally with molecular applications in entomology, and it is here that the work on non-Drosopholid insects most clearly comes to the forefront. The fascinating array of sex determination systems in insects is described in Chapter 10, although here again much space is devoted to Drosophila as an implied “model” system. The same pattern is seen in Chapter 11 (behavior), but the Þnal treatments of systematics and evolution (Chapter 12), molecular ecology (Chapter 13), and transgenic applications (Chapter 14) contain some great information and are refreshingly free of the heavy Drosophila emphasis. A good index is also important for any book, but this one needs some work. For example, the index listing for “B chromosomes” says “see Chromosome.” Under “Chromosome,” the sublisting for “B” says “see Chromosome, accessory.” The “Chromosome, accessory” subheading, though, doesnOt provide any direction to help you Þnd material speciÞc to B chromosomes. Likewise, the index listing for “constitutive heterochromatin” says “seeHeterochromatin.” The index listing for “Heterochromatin” lists six different sets of pages, but none of these indicates whether they are speciÞc to constitutive heterochromatin. Also, directions to information on some concepts such as base composition(sometimes listed asA-TorG-Ccontent) that represent topics of fundamental interest in insects and that are mentioned in the text cannot be found at all in the index. Again though, overall, this book is a great contribution toward the development of molecular ento