A Preliminary Study On The Systematic Response Of Plant Root To Insect Herbivory

In the long-term evolution of plants,in order to adapt to the stimulations brought by different environmental factors in nature,plants have equipped themselves with a series of defense responses,including systemic responses.How the systemic response occurs in plants,as well as the physiological changes and signal factors in plants during the process of systemic response,is one of the hot topics for researchers domestic and abroad.Some plant species of the genus Nicotiana are important models in studying plant-insect interactions,especially the wild tobacco(Nicotiana attenuata).Nicotine produced in the Nicotiana plants are important anti-insect metabolites.After leaves are attacked by insects,nicotine is produced in roots and transported to leaves.How insect feeding induces systemic responses to control nicotine biosynthesis remains unclear.In this thesis,the Nicotiana attenuata was treated with exogenous jasmonic acid methyl ester(MeJA)and simulated insect herbivory(WOS),and secondary metabolites,hormones,and transcriptomes,were analyzed,in order to gain insight into the systemic response in the underground plant part after the aboveground part is challenged with different external environment stimulation.After supplementation of Me JAfor 4 8 h.root nicotine content highly increased.After 2 h of treatment,the root JA,JA-Ile and IAA content significantly reduced,but their contents recovered 8 h after treatment,suggests that 2 h after applying MeJA roots systemically responded to stimuli,and continue even after 8 h.After the leaves were treated with simulated insect herbivory(WOS),after 48 ha marked increase in root nicotine content was detected.In root after 2 h and 8 h,JA and JA-Ile contents were significantly decreased,but the roots showed significantly increased IAA content.The root hormone levels almost returned to become control levels after 8 h.These data indicate that WOS treatment can induce systemic responses in plant hormones and secondary metabolites related to insect resistance.By transcriptome analysis,it was found that after treatment on leaves,in roots,the significantly responsive pathways were mainly concentrated in the metabolic pathway and the secondary metabolite pathway.In addition to the systemic signaling within plants,systemic signals also move between parasitic plants and host plants.Orobanche and Phelipanche are typical root parasites.They use haustoria to attach to host roots and extract water and nutrients and transport macromolecules,such as proteins and RNAs.In addition,very likely systemic signals are transferred between host plants and these root parasites.In this thesis,the cultivation system composed of host plants and Phelipanche plants was established and optimized,and the changes of nicotine content in Phelipanche and host plants after insect feeding on Phelipanche were preliminarily explored,which provide a basis for us to understand the interaction between root parasites and host plants and the systemic communication between above-and underground parts of plants.