|ZHANG, CHUNNI - Northwest Agriculture And Forestry University|
|WONG, ANDREW - University Of Arizona|
|ZHANG, YALIN - Northwest Agriculture And Forestry University|
|LI, XIANCHUN - University Of Arizona|
Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/26/2014
Publication Date: 9/29/2014
Citation: Zhang, C., Wong, A., Zhang, Y., Ni, X., Li, X. 2014. Common and unique cis-acting elements mediate xanthotoxin and flavone induction of the generalist P450 CYP321A1. Scientific Reports. 4:6490.
Interpretive Summary: How plant-feeding insects increase production of their detoxification capabilities (or enzymes) in response to diverse plant toxins present in their host plants remains largely unknown. We choose an important agricultural pest - corn earworm (also known as cotton bollworm) to answer a basic question of whether an insect uses different set of toxin-responsive regulatory elements or the same set of functionally more diverse regulatory elements to increase production of their detoxification capabilities (or enzymes) in response to structurally different plant toxins. Two structurally different plant toxins with very different encounter rate —xanthotoxin and flavone—were found to be capable of increasing production of a plant toxin degradation gene (CYP321A1) in the corn earworm. Seven xanthotoxin-responsive regulatory elements were defined or localized by analyzing promoter activities in corn earworm fatbody cells. Compared with the five flavone-responsive regulatory elements defined previously, there are four common regulatory elements that facilitate the induction of CYP321A1 by both of the two plant-derived toxins. These results indicate that xanthotoxin- and flavone-induced expressions of CYP321A1 are mediated mainly by the functionally more diverse common regulatory elements, although the plant toxin-specific regulatory elements are also important.
Technical Abstract: How polyphagous herbivores up-regulate their counterdefense genes in response to a broad range of structurally different allelochemicals remains largely unknown. To test whether this is accomplished by having more allelochemical-response elements or the similar number of functionally more diverse elements, we mapped out and compared the cis-acting elements mediating the induction of the allelochemical-metabolizing CYP321A1 from the generalist Helicoverpa zea by xanthotoxin and flavone, two structurally distinct allelochemicals with very different encounter rate by this species. Seven xanthotoxin-responsive elements were defined or localized by analyzing promoter activities of varying length of CYP321A1 promoter in H. zea fatbody cells. Compared with the 5 flavone-responsive elements mapped out previously, there are four common elements (1 essential element, 2 enhancers, and 1 negative element) mediating induction of CYP321A1 by both of the two allelochemicals. The remaining four elements (3 enhancers and 1 negative element), however, only regulate induction of CYP321A1 by either of the two allelochemicals. Co-administration of the two allelochemicals resulted in an induction fold that is significantly lower than the expected additive value of the two allelochemicals. These results indicate that xanthotoxin- and flavone-induced expressions of CYP321A1 are mediated mainly by the functionally more diverse common elements although the allelochemical-unique elements also play a role.