| Host plants can protect against pests through induced resistance,which is an important factor for ecological management of pests.Poplar is one of the most important cultivated tree species in China,while Micromelalopha sieversi(Staudinger)cause great damage on their economic and ecological benefit.Populus clones are abundant in variety,and the difference between clones and their induced resistance is the basis of ecological control of pests.At present,researches on the prevention and control of M.sieversi mainly focus on the chemical and biological control after the occurrence of insect pests,there is a few studies on pest prevention through trees’ own resistance.There are more studies on the resistance induced by feeding and fewer studies on the resistance induced by oviposition.The induced resistance of egg deposition of M.sieversi on clones of section Aigeiros were explored to provide the theoretical basis for induced resistance utilization.The study on the induced resistance of oviposition of M.sieversi was conducted with two clones of section Aigeiros,with ‘108’(P.× euramericana ‘Guariento’)being more attractive to M.sieversi than ‘111’(P.× euramericana ‘Bellotto’).Three treatment(oviposited plants,neighboring plants,and control plants)were set up.The oviposition amount of the three treatment plants was counted and the volatiles at 24 h,48 h and 72 h after oviposition were collected for GC-MS analysis.In electroantennogram test of five volatile compounds on the males,females and mating females,the maximum response dose was dropped on the plants leaves to statistics the number of eggs.At the same time,the survival rate of the larva feeding with the leaves of the three treatments plants were observed,and the contents of soluble sugar,total nitrogen,free amino acid,tannin and total phenol in the leaves of the three treatments were measured.In addition,Illumina Hi Seq 2000 high-throughput sequencing technology was used to analyze the transcriptome sequencing and gene expression differences in the leaves of the three treatment plants.The main research results were as follows:(1)Significantly fewer eggs were oviposited on neighboring plants compared to control plants for ‘108’ and ‘111’ after oviposition of M.sieversi,with more eggs being laid on oviposited and control plants of ‘108’ compared to ‘111’.In addition,once egg masses appeared on ‘108’ and ‘111’,the number of eggs basically remained unchanged until the end of the egg incubation period.(2)GC-MS was used to qualitatively and quantitatively analyze the oviposited plants,neighboring plants,and control plants after oviposition of M.sieversi.The relative contents of methyl palmitate,2-ethylhexyl acrylate,β-pinene,3-carene,and styrene were changed.β-Pinene was detected in oviposited and neighboring plants,but not control plants for either clone.The relative content of 3-carene in oviposited and neighboring plants of ‘108’ and ‘111’was significantly higher than that of control plants at 24 h,48 h,and 72 h after oviposition.Males,females,and mated females had the highest response to methyl palmitate and2-ethylhexyl acrylate at 50 ng/μL,and to 3-carene and β-pinene at 5 ng/μL,and to styrene at 10ng/μL in electroantennogram(EAG)assays.When using these concentrations on the plants leaves,3-carene,β-pinene,and styrene significantly reduced the number of eggs laid on ‘108’,while 3-carene and β-pinene were effective for ‘111’.(3)There was no significant difference in the survival rate of larval between three treatments plants of ‘108’ and ‘111’,respectively.The content of soluble total sugar in the oviposited and neighboring plants of ‘108’ was significantly lower than that of the control plants.The content of disaccharide and total nitrogen in the oviposited and neighboring plants of ‘111’ was significantly lower than that of the control plants,and the content of free amino acids in the oviposited plants was significantly lower than that of the control plants.At the same time,the total amount of free amino acids in the neighboring plants of ‘108’ was significantly higher than that of the oviposited and the control plants.The ratio of total sugar to total nitrogen in the oviposited and neighboring plants of ‘111’ were significantly higher than those of the control plants.The content of tannin and total phenol in the oviposited plants of‘108’ were significantly higher than that of the control plants,while there was no significant difference between the neighboring plants and the control plants.The content of tannins andtotal phenol in the oviposited plants of ‘111’ was significantly higher than that in the control plants,and the content of tannins in the neighboring plants was significantly higher than that of the control plants.(4)We obtained a total of 304,526,107 reads with an average length of 300 bp and a total of 40.77 Gb size.After filtering,we aligned the clean reads to the reference genome of P.trichocarpa and 63.60 % of the clean reads could be aligned to the reference genome.There were 571(408 up-regulated and 163 down-regulated)and 48(16 up-regulated and 32down-regulated)significantly differentially expressed genes in the oviposited leaves and neighboring leaves of ‘108’,respectively.There were 1234(433 up-regulated and 801down-regulated)and 1784(173 up-regulated and 1611 down-regulated)significant differentially expressed genes in the oviposited leaves and neighboring leaves of ‘111’,respectively.There were 2830,276,6310 and 9338 genes with significant differences according to the functional annotated and pathway analysis between the four control groups(108-O vs 108-C,108-N vs 108-C,111-O vs 111-C,111-N vs 111-C),and which mainly involved 42,30,44,and 46 biological function respectively,functional subclasses of biological process,cell component and molecular function.The differentially expressed genes were mainly involved in such functions as “cell part”,“catalytic” and “metabolic process”.The genes were enriched in the metabolic pathways of plant pathogenic bacteria,linolenic acid and cyano-amino acids in oviposited leaves of ‘108’,and there was no significant enrichment pathway in neighboring leaves.The differentially expressed genes in oviposited leaves of ‘111’were enriched in metabolic pathway,photosynthesis,photosynthetic-antenna protein,nitrogen metabolism and linolenic acid metabolism pathway,and the differentially expressed genes in the neighboring leaves ‘111’ were enriched in the metabolic pathway and the secondary metabolic material synthesis pathway.The defense genes related to PR protein,innate immune regulation and biological stress response in the oviposited and neighboring leaves of ‘108’ and‘111’ were up-regulated respectively,but the specific genes were different,and the genes related to photosynthetic activity were all significantly down-regulated.In the studies on induced resistance of oviposition of M.sieversi,the oviposited plants and neighboring plants of P.× euramericana ‘Guariento’ and P.× euramericana ‘Bellotto’exhibited defense responses.3-Carene and β-pinene were used as chemical signals between plants to effectively reduce the number of eggs.At the same time,the content of nutrients in the oviposited and neighboring plants changed and the content of secondary metabolites increased to different degrees,which improved their chemical defense ability.At the molecular level,the differentially expressed genes of oviposited and neighboring plants involve functional genes such as “cell parts”,“catalytic” and “metabolic processes”,and defense genes related to resistance,as well as resistance mechanisms such as decreased photosynthesis and nutrient accumulation,and increased synthesis of secondary metabolites.The oviposition of M.sieversi induced the oviposited plants and neighboring plants of the two clones the resistance responses at the physiological,biochemical and molecular levels. |
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