Exploring the role of CYP6AB328 in spinetoram resistance and growth and development of Phthorimaea absoluta.

Phthorimaea absoluta is a major agricultural pest, affecting tomatoes and other solanaceous crops. Insect cytochrome P450 is a key enzyme that metabolizes xenobiotics (insecticides and plant toxins) and regulates endogenous compounds, but the functions of specific CYP genes in P. absoluta remain unclear. This study analyzed the expression pattern of 97 CYP genes in two regional populations of P. absoluta from Xinjiang, China. CYP6AB328 was identified as the most significantly overexpressed in the strain from Yining city (YN) compared to the strain from Alaer city (Ala), its expression level exhibited a positively correlated with the accumulating resistance of spinetoram. Following the cloning and sequence analysis of the target gene, it was named CYP6AB328. Additionally, a leaflet delivery system demonstrated the relatively stable presence of dsCYP6AB328 in the leaves from 12 to 24 h. The expression level of CYP6AB328 was significantly reduced by 68.9 % in 2nd instar larvae treated with 7.5 μg/200 μL dsCYP6AB328 at 48 h. Knockdown CYP6AB328 significantly increased susceptibility to spinetoram in the SPI-S strain (belongs to YN strain) and markedly decreased the spinetoram resistance ratio in the resistant strain (SPI-R: 250.57-fold). Notably, silencing CYP6AB328 inhibited nearly all 1st instar larvae fully mining the leaves, resulting in mortality up to 95.3 %, while in 2nd instar larvae, it prolonged leaf-mining time, reduced leaf damage, extended the development time of 2nd to 4th instar, caused 18 % larval abnormality and achieved an 84.4 % mortality on the 6th day of treatment. In summary, our findings indicate that CYP6AB328 plays an important role in promoting development of spinetoram resistance and growth and development of P. absoluta.