The Physiological Response To Autotoxicity In Melon Root And Analysis Of Gene Expression Profiles Associated With Autotoxicity

Toxicity is the key reason for melon continuous cropping obstacles.Using melon cultivated variety "New Silverlit" as the research material,we analyse the allelopathic of melon and its mechanism by studying melon's seeds and plants after the treatment by melon plant aqueous extracts.Differential expression genes in melon allelopathic autotoxicity induced by plant aqueous extracts were analyzed by Digital Gene Expression Profiling in this study.Some crucial genes related to melon autotoxicity were cloned and tested.R2R3-MYB transcription factor were transformed into melon by Agrobacterium tumefaciens-mediated transformation.The main results are as follows:1.The physiological response to autoxicity in melon rootWe study the effct of autotoxicity in melon by observing melon's primary roots formation and physiological and biochemical changes after the treatment by melon plant aqueous extracts.The results showed that plant extracts had some inhibiting effects on the growth of melon's primary root,and the root in morphology was changed dramatically under different stress treatments.The taproot became shorter and wider,the root tip was roted slightly,and the number of lateral roots increased.The change of physiological and biochemical indexes present a certain regularity.The effect of SOD activity and the content of MDA in root increased with the extension of stress time,the effect of CAT activity and the content of soluble protent rised firstly and then decreased,and the effect of POD activity first decreased and then rised.2.Sequencing and analysis of Digital Gene Expression Profiling associated autotoxicity in melonMelon seedlings after treatment of plant aqueous extracts were digitally sequenced by Solexa sequencing technology.And large amounts of stress-related gene were found.The expression pattern of differentially expressed genes in melon can be divided into 4 categories:upward adjustment,downward adjustment,sustained and instantaneous expression.The numbers of differentially expressed genes were 1323 in sample 2d,and were 331 in sample 4d.The former was about 4 times of the latter.The most of differential expression genes were up-regulated.These differences are mainly concentrated in the ribosomal genes,photosynthetic pathway,the metabolic pathways of phenylpropanoid pathway,and the flavonoids synthesis pathway etc.3.The expression of genes associated flavonoid pathway in melonRelative expression level of 6 structural genes and 3 regulatory factors in melon allelopathic autotoxicity induced by plant aqueous extracts were analyzed by real time fluorescent quantitative PCR technology in this study.It was found that different genes had its own expression pattern.Relative expression level of PAL gene and CHI gene in leaf increased with the extension of stress time.The expression of C4H gene and CHS gene had some volatility in stress process.Relative expression level of 4CL gene,bHLH gene and R2R3-MYB transcription factor rised first and then decreased.And reached the maximum value in 2d.The expression of 4CL gene was regulated by bHLH gene and R2R3-MYB transcription factor.4.Cloning and genetic transformation of one related autotoxicity MYB transcription factor were transformed in melonR2R3-MYB transcription factor of melon were introduced into the melon by using Agrobacterium mediated method,and transformed callus identified by PCR.The results showed that R2R3-MYB transcription factor has been successfully integrated into the genome of muskmelon.