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| Expression of Endogenous Signal Molecules and Gene in Wound Response of Brassica rapa subsp. pekinensis |
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Abstract Chinese cabbage (Brassica rapa subsp. pekinensis) will be subjected to mechanical damage during growing, cultivation, processing and transportation. In this study, Chinese cabbage was processed by injury treatment, then the production of jasmonic acid (JA), ethylene (ET) and salicylic acid (SA) were detected using gas chromatography-mass spectrometry (GC-MS), GC and high performance liquid chromatography (HPLC), respectively. The transcripts of genes involved in wounding response were detected by cDNA microarray analysis. The expression level of the marker genes were measured by cDNA microarray analysis and semiquantitative RT-PCR. The results of cDNA microarray analysis showed that a large number of genes were up-regulated after wounding, which included transcription factor, small GTP-binding protein, receptor-like protein kinase, protein kinase, the genes for JA/ET biosynthesis, defence-related genes, the genes involved in glucosinolates degradation, the genes for tryptophan biosynthesis, the genes for modifying cell wall, the genes invovled in alkaloid and phenylpropanoid metabolic pathways and several molecular chaperones. The analysis of JA content showed that the production of JA was significantly higher in the wounding leaves than that in the non-wounding leaves at 6, 12, 24 and 48 h. Gene expression analysis showed that the key genes for JA biosynthesis which included allene oxide synthase (AOS), allene oxide cyclase (AOC), lipoxygenase (LOX), the phospholipase D (PLD) which occur in the upstream of JA biosynthesis and the JA-responsive marker gene, myrosinase-associated protein (MYAP) were up-regulated after wounding. The results indicated that JA signaling pathway might play an important role in the wounding response. The result of ET generation indicated that ET rapidly produced at 2 and 6 h after wounding treatment. Gene expression analysis for ET signal pathway showed that the key genes for ET biosynthesis, 1-aminocyclopropane-1- carboxylicacid (ACC) synthase 6 (ACS6) and ACC oxidase (ACO) were up-regulated at the early stage during wounding response process, and the ethylene-responsive transcription factor 4 (ERF4) was up-regulated at 0.17, 0.5, 2, 6, 12 and 24 h after wounding. These results indicated that ET signaling pathway participated in early wounding response. Both JA and ET required β-1,3 glucanase (BGL), and the expression of BGL was up-regulated at all time points which indicated that JA and ET coordinately regulated the wounding response. The contents of free and total SA were significantly decreased after wounding. The marker genes of SA signaling pathway, pathogenesis-related protein 1a (PR1a) and PR5, were down-regulated or unchanged at the early stages of wounding response, and up-regulated at the late stages during wounding response. It indicated that SA signaling pathway was suppressed at the early stage and activitied at the late stage, and involved in the defence response at the late stages of wounding response. This study clarified that some genes in the transcriptome were involved in the wounding response, and the production of JA, ET and SA and the expression level of the genes for JA, ET and SA signaling pathway were after wounding treatment. This finding is helpful to reveal the defense mechanism of the wounding response in Chinese cabbage.
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Received: 15 December 2015
Published: 06 May 2016
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