The ABCs of CRISPR in Tephritidae: developing methods for inducing heritable mutations in the genera Anastrepha, Bactrocera and Ceratitis.

Tephritid fruit flies are destructive agricultural pests that are the targets of expensive population eradication and suppression efforts. Genetic pest management is one of the strategies for reducing or eliminating tephritid populations, relying upon the genetic manipulation of insects to render them sterile or capable of transmitting deleterious traits through gene drive. Currently, radiation, chemical mutagenesis, and transgenic techniques are employed to generate agents for genetic pest management, but new methods must be explored and developed for all tephritid pest species. Targeted mutagenesis induced by nonhomologous end join repair of clustered regularly interspaced short palindromic repeats and the CRISPR associated protein 9 (Cas9) (commonly known as CRISPR/Cas9) has been demonstrated to be an efficient method for creating knock-out mutants and can be utilized to create germline mutations in Tephritidae. In this paper, we describe detailed methods to knockout the white gene in three tephritid species in the genera Anastrepha, Bactrocera and Ceratitis, including the first demonstration of CRISPR/Cas9 induced mutations in the genus Anastrepha. Lastly, we discuss the variables in tephritid systems that directed method development as well as recommendations for performing injections in remote containment facilities with little molecular biology capabilities. These methods and recommendations combined can serve as a guide for others to use in pursuit of developing CRISPR/Cas9 methods in tephritid systems.

A field test for host fruit odour discrimination and avoidance behaviour for Rhagoletis pomonella flies in the western United States.

Prezygotic isolation due to habitat choice is important to many models of speciation-with-gene-flow. Habitat choice is usually thought to occur through positive preferences of organisms for particular environments. However, avoidance of non-natal environments may also play a role in choice and have repercussions for post-zygotic isolation that preference does not. The recent host shift of Rhagoletis pomonella (Diptera: Tephritidae) from downy hawthorn, Crataegus mollis, to introduced apple, Malus domestica, in the eastern United States is a model for speciation-with-gene-flow. However, the fly is also present in the western United States where it was likely introduced via infested apples ≤ 60 years ago. R. pomonella now attacks two additional hawthorns in the west, the native C. douglasii (black hawthorn) and the introduced C. monogyna (English ornamental hawthorn). Flight tunnel tests have shown that western apple-, C. douglasii- and C. monogyna-origin flies all positively orient to fruit volatile blends of their respective natal hosts in flight tunnel assays. Here, we show that these laboratory differences translate to nature through field-trapping studies of flies in the state of Washington. Moreover, western R. pomonella display both positive orientation to their respective natal fruit volatiles and avoidance behaviour (negative orientation) to non-natal volatiles. Our results are consistent with the existence of behaviourally differentiated host races of R. pomonella in the west. In addition, the rapid evolution of avoidance behaviour appears to be a general phenomenon for R. pomonella during host shifts, as the eastern apple and downy hawthorn host races also are antagonized by non-natal fruit volatiles.

Pharyngo-enteral anastomosis for esophageal reconstruction in diffuse corrosive esophageal stricture.

BACKGROUND: Diseases involving the entire esophagus usually require extensive surgical procedures to accomplish functional reconstruction. These procedures are extremely stressful for undernourished patients. We have utilized a simpler procedure for total esophageal reconstruction. METHODS: This retrospective report reviews the experience in 8 patients who underwent esophageal reconstruction by pharyngo-colo-gastrostomy or jejunostomy without any resection of bony structures. RESULTS: There was no operative or hospital death. Complications included anastomotic stenosis, transient leak from the ileal stump, and late enterocutaneous fistula, each in 1 patient. Laryngeal function was maintained without special treatments. After swallowing training for approximately 1 week, oral feeding was resumed. All patients have gained 7 to 21 kg at 35 to 67 months after surgery. CONCLUSIONS: Our surgical procedure is shown to be safe and effective in undernourished patients with diffuse esophageal stricture.