| Grafting is a widely used ancient gardening technique which can improve plant resistance to biotic and abiotic stresses and maintain excellent traits.After grafting,the plants first activate wounding response due to cutting accompanied by asymmetric expressing of sugar-responsive genes in the upper and lower sides of the incision.Then goes into a continuous wound healing process,with the genes expressed symmetrically.Symmetrical gene expressing between rootstock and scion is the basis of grafting compatible.Whether Jasmonic acid(JA),which is the first stressresponsive hormone in plants,expressed symmetrically or not after wounding remains largely unclear.To address this question,we take advantage of hypocotyl micro-grafting,UPLC-MS and q PCR to analyze the dynamics changes of JA and its active product Jasmonate Isoleucine(JA-Ile),as well as the transcription levels of 30 JA-related genes,in the early stage of micro-grafting(within 12 hours)in grafted and un-grafted tomato.The results are as follows:First of all,the abundance of JA and JA-Ile are significantly different between the upper and lower side of the incision before micro-grafting,while getting equal after micro-grafting.The abundance of JA-Ile began to recover at 2 h after grafting and became normal at 6 h in treatment group,while that in the control group showed no recovery even after 12 h.Furthermore,we found the expression pattern of 11 genes were changed after micro-grafting.The expression pattern of 5 genes among them,that is SlLOX11 and SlAOS(JA biosynthesis related genes),SlCOI1(JA signaling related gene),SlJA2 L and SlLAPA(JA defense related genes),changes from un-related to significant related at both ends of the incision.The expression pattern of another 5 genes,including one JA signal transaction gene(SlJAZ1),four JA signal controlling genes(Solyc01g090560 SlERF?Solyc06g075510 SlERF?Solyc02g070040 SlERF and SlHD-Zip),presented more correlation between upper and lower side at the incision after grafting.The expression pattern of Solyc01g090320 SlERF,however,turns from related to un-related between upper and lower side at the incision after grafting.Subsequently,we compared the peak expression levels of 30 JA-related genes in tomato rootstock and scion within 12 h.The results showed that the peak expression of most genes in rootstock was higher than that in scion after micro-grafting treatment,and the gene expressions were induced by micro-grafting after 2 h both in tomato rootstock and scion.However,the gene expressions in scion at 12 h were repressed significantly compared to control groups as time went by,while that in rootstock still keep elevating.Besides,we also found the response of MYC2-JAZ2L-TD cascade changes at incision both in tomato rootstock and scion after micro-grafting.In summary,we found that the micro-grafting induced wound healing alleviates the asymmetric accumulation of JA and JA-Ile and the decreasing trend of JA-Ile in tomato scions and stocks caused by wounding.Screen out 11 genes whose expression patterns changed significantly in scions and stocks before and after grafting,which indicated that micro-grafting alleviated the asymmetric response of JA-related genes caused by wounding in the early stage in tomato scions and stocks,and it is worth noting that the JA-related genes were changed more significantly in the scion after micro-grafting within 12 h.The SlMYC2-SlJA2L-SlTD cascade response was enhanced in the rootstock after grafting,but it was significantly reduced in the scion.The above results uncovered the effect of micro-grafting on the JA response and the asymmetric mechanism of JArelated genes expression caused by wounding,and screened out the genes with significant changes in expression patterns before and after micro-grafting,which laid the foundation for further investigation of key factors of grafting compatibility in plants. |
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