TOR Signaling Pathway In Cotton And The Molecular Mechanism Of Its Crosstalk With JA Signaling Pathway

Cotton especially upland cotton(Gossypium hirsutum)provides the major resource of textile fiber worldwide,is one of the most important cash crops and plays a key role in the development of national economies.Environmental stress significantly influences cotton yield.To deal with environmental stresses,crops like cotton frequently encounter yield penalties resulting from effects of environmental stresses on development.Target of rapamycin(TOR)signaling pathway functions as a key regulator of growth and development,and is highly conserved in in eukaryotes.Jasmonic acid(JA)signaling pathway,as an important plant hormone,extensively involves in response to stresses.Dissecting the underlying genetic components and the mechanistic insights linking TOR and JA signaling pathways in plants may provide a strategy to improve resistance against environmental stress and reduce production losses,which has a great significance to the crop production.This study makes a preliminary study of the crosstalk between TOR and JA signaling pathways in cotton and Arabidopsis.Results are shown below:1.By the bioinformatics analysis in the recently sequenced Gossypium hirsutum genome database,for the first time,we found that TOR signaling pathway also existed in cotton.We found the key proteins of TOR complex 1(TORC1)was highly conserved;however,no putative homologs of TORC2-specific proteins,such as RICTOR and SIN1,were present in the cotton genome.There were two TOR genes in cotton,which showed high similarities with homologs of Arabidopsis,humans and yeasts.Besides,compared with other components in TOR signaling pathway,RAPTOR,S6 K,and RPS6 extensively expanded,suggestting that TOR/RAPTOR-S6K-RPS6 signaling cascade may act as the mainstay of TOR signaling pathway and play highly conserved roles in controlling cell growth and proliferation in cotton.2.The pharmacological analysis revealed that cotton seedlings were insensitive to the first generation TOR inhibitor rapamycin,whereas the second generation TOR inhibitor AZD8055 can significantly inhibit the growth of cotton seedlings in a dose dependent manner.To further dissect cotton TOR function,analysis of transcriptome of TOR inhibited cotton seedlings was preformed.A total of 6419 differentially expressed unigenes(DEG)were identified between control and TOR inhibited seedlings;3767 were up-regulated and 2652 were down-regulated.The results of RNA-seq data revealed that the transcript levels of plant hormones JA,auxin and abscisic acid related genes were significantly changed.3.The crosstalk between TOR and JA signaling pathways.This study revealed that TOR inihibitors and methyl jasmonate(Me JA)could synergistically inhibit plant growth;TOR inhibition result in a dramatic increase in the amount of endogenous JA content;quantitative realtime PCR analysis suggested that TOR inhibition could significantly alter the transcript levels of JA synthesis and signal transduction related genes;JA biosynthetic and signaling mutants displayed TOR inhibitor-resistant phenotypes compared with wildtype plants;we cloned 21 cotton TIFY genes and transformed them intoyeast FKBP12-based Arabidopsis transgenic plants(BP12-2),and found that cotton TIFY overexpression can partially rescue TOR-suppressed phenotypes in Arabidopsis.The results above indicated that the crosstalk between TOR and JA pathway exists in cotton and Arabidopsis,which may play an important role in improving crop yield and their ability of tolerating stress.