Regulation Of Flavonoids Degraded By Lactase-phlorizin Hydrolase On The Development Of Oedaleus Asiaticus

Oedaleus asiaticus Bey-Bienko,one of important pests in northern China,causes serious damage to the grassland ecosystem.We studied the feeding characteristics on three species of gramineous plants in the Inner Mongolia grassland to clarify the feeding preferences and the adaptation mechanism to host plants in O.asiaticus.Previous studies have found that different plant treatments cause significantly differential expressions of the lactase-phlorizin hydrolase(LPH) gene,suggesting that LPH mediates plant secondary metabolite flavonoids to jointly regulate the growth and development of O.asiaticus.Therefore,the ecological and molecular studies were conducted to clarify the feeding characteristics of O.asiaticus,and the mechanism of LPH and plant secondary metabolite-mediated insulin-like pathway(ILP) affecting the growth and development of O.asiaticus.The main results are as follows:1.Compared with Leymus chinensis,Stipa krylovii and Cleistogenes squarrosa had the largest effect on the development of O.asiaticus.O.asiaticus prefered to feed on S.krylovii and C.squarrosa.The feeding position had nothing to do with the height of gramineous plants,but mainly fed on the lower middle part of plants(9?10 cm above the ground),and the upper middle part of plants dropped,which often caused leaf drop and damage,and affected the growth and development of plants,resulting in the loss of animal husbandry and herbage yield.Compared with the typical steppe with L.chinensis as the dominant plant,the typical steppe with S.krylovii and C.squarrosa as the dominant vegetation is likely more suitable to the occurrence of O.asiaticus.2.LPH could play an important role in the growth and development of O.asiaticus.Lph dsRNA and LPH inhibitor treatments inhibited LPH at the transcription level and protein level,respectively,which inhibited the relative expression of key genes and the phosphorylation level of key proteins in the insulin-like signaling pathway IGF?FOXO cascade,thus delaying the growth and development of O.asiaticus.3.Plant producing secondary metabolites is an important way that plants have evolved to resist insect pests.When quercetin,a flavonoid secondary substance,was used to rear O.asiaticus,it was found that high concentration of quercetin delayed its growth and development.Molecular biological experiments showed that quercetin,as a plant secondary metabolite,could inhibit the insulin-like signaling pathway,and significantly down-regulated the relative expression of key genes and the phosphorylation level of key proteins in the IGF?FOXO cascade pathway,meanwhile reactive oxygen explode in vivo.On the other hand,the activity of protective enzymes such as MFO,POD,SOD and CAT in O.asiaticus was significantly increased but the activity of PO was inhibited.