Sirex noctilio eggs and emerging larvae, The black scale bar at the bottom of the picture represents 1mm.Credit: Elmarie van der Merwe
Researchers at the University of Pretoria have discovered a new way to speed up genetic studies of Sirex woodwasp, an invasive species that attacks pine plantations and threatens the South African forestry industry.
A study published in Insects shows how researchers found a way to activate wasp eggs by squeezing them by hand to produce larger numbers to study their genes. The method opens avenues for research on Sirex noctilio's physiology, ecology, symbioses, and genetics, providing potential insights for new pest management strategies.
Lead researcher, Gudrun Dittrich-Schroder and her team made the breakthrough by activating Sirex noctilio eggs mechanically, by squeezing the eggs to get them ready to hatch. Dittrich-Schroder's journey into Sirex noctilio research stems from a broader mission to develop genetic pest control management strategies.
“In order to create these transformed individuals you inject the CRISPR-Cas9 with the guide RNA into the eggs to target the gene that you want,” Dittrich-Schroder says.
“We need to access lots of eggs because the success rate of micro-injected eggs is less than 10%.”
CRISPR/Cas-9 gene editing is adopted from acquired immunity in prokaryotes and consists of two elements: guide RNA used to locate (bind) the target DNA to be edited and Cas-9, a protein that essentially cuts the DNA at the location identified by guide RNA.
They used a double-slide compression technique, a quick and efficient method requiring no specialised equipment. This approach proved instrumental in activating Sirex noctilio eggs, marking the first successful attempt to dissect and activate the eggs ex vivo.
The team collected logs containing woodwasps from the Western Cape and Mpumalanga, waited for the females to emerge, removed the eggs, and activated them using their new technique.
“We were like mothers. Watching these eggs to see their development, checking them under the microscope each day, and it was really very exciting because this had never been done before and it just seemed like such an almost too simple way for it to work.”
