OsMYB Regulates Weed Control In Allelopathy Rice

Allelopathic rice regulates the allelochemicals synthesis by regulating theexpression of transcription factors and genes involved in the synthesis of secondarymetabolites. The allelopathy process is contigent upon these genes and theirinteractions. In this thesis, allelopathic rice PI312777was used as the material toobtain the OsMYB (CT829537) TF overexpression(OE) and silent transgenic rice bygene overexpression and RNAi techniques. qRT-PCR was utilized to analyze theexpression of seven key genes in benzene propane metabolic pathways, i.e.,Phenylalanine ammonia-lyase(PAL), Cinnamate-4-hydroxylase(C4H), Hydroxylase,CoA-ligases(CAL), O-Methyltransferases(4CL), Cinnamoyl-CoA(CCA), Cinnamoylalcohol dehydrogenases and six key genes in isoprene metabolic pathways, i.e.,Mevalonate kinase(T1), Monoterpenes synthase(T2), Sesquiterpene synthase(T3),Diterpene synthase(T4), Phytoene synthase(T5), Squalene synthase(T6) in wild-typeand transgenic rice root. The content of total phenols in transgenic rice roots and rootexudates were determined by Folin-Ciocalteu colorimetric method. Meanwhile, thesix kinds of major phenolic acids (Catechuic acid, Caffeic acid,4-Hydroxybenzoicacid, Chlorogenic acid, Ferulic acid, Cinnamic acid) were detected by HPLC. Thecontent of terprnoids in the transgenic rice roots and root exudates was detected byGC-MS. Further, the allelopathy of transgenic rice was evaluated by bioassay. Basedon this, this thesis analyzed the CT829537TF by phylogenetic tree and subcellularlocalization, screened the interaction protein by His-pulldown and CO-IP andscreened the target genes of the OsMYB CT829537TF by immunoprecipitation.The results could be summarized as follows:(1) After co-cultured with BYG for7days, the7key genes in the phenylpropanoid pathway in OsMYB-RNAi transgenicrice PI312777were all downregulated (PAL,4CL, CCA, HYL, downregulated1.5fold,6.68fold,4.2fold and4.08fold, respectely) except the C4H gene showedupregulation. The6key genes in the isoprene metabolic pathway were alldownregulated except the Diterpene synthase gene, which showed a5.27foldupregulation. In the OsMYB-OE transgenic rice PI312777, the7key genes in the phenylpropanoid pathway were all upregulated (PAL3fold, CAD7.26fold, HYL4fold, OMT3.73fold),6key genes in the isoprene metabolic pathway were allupregulated (T19.85fold, T28fold, T34.62fold, T41.07fold, T51.55fold, T66.32fold).(2) The results of Folin-Ciocalteu colorimetric method showed that the content oftotal phenol acids in the rice root and root exudates had the same tendence, i.e.,OsMYB-OE>WT>OsMYB-RNAi and OsMYB-OE+BYG>WT+BYG>OsMYB-RNAi+BYG. The results of HPLC showed that the release of phenolic acids in theRNAi transgenic rice were lower than WT about0.64fold, and the OsMYB-OEtransgenic rice was1.35times than the WT rice. The results of the GC-MS alsoshowed that the terpenoids content in RNAi transgenic rice root exudates was lowerthan WT rice about0.77fold, and the OsMYB-OE transgenic rice showed1.31foldcompared to the WT rice. The bioassay results showed that the inhibition rate(IR) ofOsMYB-OE transgenic rice was36.7%, which was higher compared to WT30.8%IRand OsMYB-RNAi transgenic rice was16.4%of IR.(3)Gene homology analysis suggested that the OsMYB CT829537had a lowhomology with the other reported R2R3-MYB TFs. Phylogenic trees analysis showedthe OsMYB CT829537has its own branch, implying a low homology with the otherR2R3-MYB TFs. The subcellular localization assay showed the OsMYB CT829537TF was located in the nucleus, which might be relevant to its functions within theorganism.(4)His-pulldown and Co-IP were employed to screen interactive proteins. The resultsshowed that under co-culture with BYG, the OsMYB CT829537TF interacted withGAPDH, Heat shock protein, NBS-LRR-like protein, Resistance proteins; screeningthe target genes of the OsMYB CT829537TF suggested that the CT829537TF mightparticipate in photosynthesis, secondary metabolites synthesis and plant stressresisitance regulation other TFs.In conclusion, with the silence of CT829537gene in the allelopathic rice, theexpression levels of allelochemicals synthesis related genes was downregulated, thesynthesis of allelochemicals decreased and the potential of allelopathy declined; on the other hand, overexpression of the CT829537gene increased the allelochemicalssynthesis related genes, the synthesis of allelochemicals and the allelopathic potential.The OSMYB CT829537TF might activate a comprehensive response toenvironmental stress to improve the chemical defense capability of allelopathic rice.