A piggyBac route to transgenic honeybees.

The honeybee Apis mellifera is one of the most recognized and revered insect species throughout human history. The economic impact of the honeybee as an essential pollinator of key crops is estimated to be in the range of billions of dollars per year. The honeybee also serves as a powerful animal model for studies of the evolution and regulation of social behaviors at the endocrine, cellular, genomic, and molecular levels (1). However, until recently, studies of molecular processes that underlie behavior in the honeybee have mainly relied on correlative genomic studies of brain gene expression patterns (2). Nevertheless, establishing a causal relationship between specific genetic loci and phenotypes has been hindered by the lack of robust and reliable methods to manipulate honeybee gene expression, the generation of transgenes, and genome editing. In PNAS, Schulte et al. (3) provide, to my knowledge, the first evidence that heritable germ-line manipulations of the honeybee genome are feasible by using engineered transposable elements. These welcome technical advances are likely to transform the fields of sociobiology and apiculture (commercial beekeeping) by helping investigators to establish causal relationships between genes and behavioral, developmental, and diseaserelated phenotypes. The development of transgenic insects is not new to biology. In fact, one of the first successful transgenic germ-line transformations of any animal genome was published in a series of groundbreaking studies in the fruit fly Drosophila melanogaster by Rubin and Spradling in the early 1980s (4). These studies were the first to show that engineered natural transposable elements, viral-like DNA sequences called “P-elements,” can be used as efficient molecular shuttles for the stable introduction of foreign DNA fragments into the fly genome. Consequently, the P-element became the workhorse of fly molecular genetics and genomics by allowing the rapid identification of affected genes in forward genetic screens of Drosophila lines that harbor P-elements inserted in protein-coding genes throughout the fly genome (5). The main discovery that allowed the adoption of natural transposons for use in molecular biology and genetics was that active transposons require just two elements to enable them to “jump” across chromosomal loci. First, the DNA sequences of most transposons harbor terminal inverted repeat (IR) sequences, which define their chromosomal boundaries. Second, all active transposons code for a transposase, an enzymes that catalyzes the cutting and pasting of the transposon from one location to another. Thus, in the presence of a transposase, any DNA sequences between the two IRs will be cut out of the present location and pasted to a new random location in the genome.