Fitness and Glucosinolate Catabolism-related Gene Expression Upon Feeding on Natural Host Plant of Plutella xylostella Raised from Artificial Diet

Glucosinolate sulfatase (GSS) and sulfatase modifying factor 1 (SUMF1) are crucial for the catabolism of Plutella xylostella on the defensive glucosinolates in the cruciferous host plants. However, little information is available on their roles in the adaptation of the strain of P. xylostella raised from an artificial diet when changed to be fed on its natural host plant. The expression patterns of GSSs and SUMF1s at different developmental stages of two artificial diet strains of P. xylostella (i.e., AD and G88) were determined. It was found that the expressions of GSSs were similar between the two strains, with abundant GSS1 and GSS2 expressions at the 3^rd and 4^th-instar stages, but no apparent patterns observed for SUMF1s. After the newly hatched larvae of AD and G88 were transferred onto the cotyledons of radish plants, the larval survival rates became lower, with longer larval developmental time and lower pupal weight, than their counterparts fed on the original artificial diet. The expression levels of GSS1 and GSS2 in the larval midguts grown on the radish cotyledons decreased significantly; but, that of SUMF1a, only in the midguts of AD strain. It suggested that the expressions of glucosinolate catabolism-related genes in P. xylostella were possibly regulated by the factor(s) in the host plant and closely associated with the adaptability of the insects upon a shifted feeding from a formulated diet to a natural host plant.