Studies On The Molecular Mechanism Of Red Light-induced Resistance Against Meloidogyne Incognita In Citrullus Lanatus

Watermelon（Citrullus lanatus）is an important economic crop in the world,but south root-knot nematodes（Meloidogyne incognita）seriously affect the yield and quality of watermelon production.In this study,our result indicated that red light could reduce the damage by root knot nematode in watermelon,which revealed that red light could induced watermelon defense resistance against nematodes.Based on the whole genome sequencing data of watermelon,the molecular mechanism of red light stimulating watermelon resistance against south root-knot nematodes was studied by using RKN-seq and metabonomics to analyze the molecular mechanism.The main results obtained were as follows:1.Watermelon（Xinong 8）was used as experimental material.Red light（RL）200mol·m^-2·s^-1（photosynthetic photon flux density）was irradiated to four-leaf watermelon seedlings with light emitting diode（LED）for 21 days.Red light reduced the watermelon damage by root knot nematode,increased whole plant and root fresh weight and dry weight.After red light&RKN treatment 7 days,PR1 and WRKY 70 gene was highly increased,the activity of antioxidant enzymes in leaves and roots,redox,content of resistant substances and hormones were all significantly changed for enhanced resistance against RKN.2.The difference of gene expression after red light and root knot nematode treatment in watermelon were analyzed by high-throughput RNA-seq technique.four（control/RL/RKN/RL+RKN）cDNA libraries were sequenced using Illumina HiSeq high-throughput sequencing platform,92.40Gb clean Data was obtained,and617,364,140 total reads were obtained.540,035,389 mapped reads from were annotated functionality.With a comparison of COG,KOG,GO,KEGG,NR,Swiss-Prot,and Pfam databases,2,188 genes were functional annotations.A total of 355 differentially expressed genes were obtained and 811 new genes were excavated,of which 547 were annotated.We screened out the anti-TIFY gene family and ethylene related gene,and WRKY gene family.Highly expressed differentially expressed genes associated with ERF family genes was also detected.3.Watermelon seeding（Xinong 8）was used as experimental material.The whole spectrum of the samples was analyzed by HILIC UHPLC-Q-TOF MS technique and data dependent collection method.The peak extraction and metabolite identification of the first and second order mass spectrometry data were carried out by XCMS.After XCMS pretreatment,4,596 peaks were detected by positive ion mode.4,732 peaks were detected in anion mode.The differences between different treatments were compared in the positive and negative ion models of metabolic products,the results showed that the contents of cottonseed sugar,sucrose,honey disaccharide,threonose and fructose,mannose and dextrose were decreased,malic acid content in the differential metabolites of tricarboxylic acid cycle increased,and the contents of fructose,mannose and dextrose increased in the different metabolites of carboxylic acid cycle.Phenylalanine,isoleucine,cytosine nucleoside,guanine nucleoside,deoxyguanosine succinic acid,palmitic acid in amino acids and organic acids were all increased.The KEGG pathway is mainly concentrated in the biosynthesis of plant hormones,phenylalanine metabolism,ubiquinone and other terpenoids biosynthesis.