sGrafting is a highly useful technique, and its success largely depends on graft union formation. In this study, we found that root-specific expression of the auxin biosynthetic gene iaaM in tobacco, when used as rootstock, resulted in more rapid callus formation and faster graft healing. However, overexpression of the auxin-inactivating iaaL gene in rootstocks delayed graft healing. We observed increased endogenous auxin levels and auxin-responsive DR5::GUS expression in scions of WT/iaaM grafts compared with those found in WT/WT grafts, which suggested that auxin is transported upward from rootstock to scion tissues. A transcriptome analysis showed that auxin enhanced graft union formation through increases in the expression of genes involved in graft healing in both rootstock and scion tissues. We also observed that the ethylene biosynthetic gene ACS1 and the ethylene-responsive gene ERF5 were upregulated in both scions and rootstocks of the WT/iaaM grafts. Furthermore, exogenous applications of the ethylene precursor ACC to the junction of WT/WT grafts promoted graft union formation, whereas application of the ethylene biosynthesis inhibitor AVG delayed graft healing in WT/WT grafts, and the observed delay was less pronounced in the WT/iaaM grafts. These results demonstrated that elevated auxin levels in the iaaM rootstock in combination with the increased auxin levels in scions caused by upward transport/diffusion enhanced graft union formation and that ethylene was partially responsible for the effects of auxin on grafting. Our findings showed that grafting success can be enhanced by increasing the auxin levels in rootstocks using transgenic or gene-editing techniques.

中文翻译：

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富含生长素的砧木对嫁接影响的分子和生理特征

sGrafting 是一种非常有用的技术，其成功很大程度上取决于移植物结合的形成。在这项研究中，我们发现生长素生物合成基因的根特异性表达国际原子能机构在烟草中，当用作砧木时，会导致更快的愈伤组织形成和更快的移植愈合。然而，生长素失活的过度表达艾尔砧木中的基因延迟了移植物愈合。我们观察到内源性生长素水平和生长素反应性增加DR5::GUSWT接穗中的表达/国际原子能机构与WT / WT嫁接中的嫁接相比，这表明生长素从砧木向上转运到接穗组织。转录组分析表明，生长素通过增加砧木和接穗组织中参与嫁接愈合的基因的表达来增强嫁接结合的形成。我们还观察到乙烯生物合成基因ACS1和乙烯反应基因ERF5在 WT/ 的接穗和砧木中均上调国际原子能机构移植物。此外，将乙烯前体 ACC 外源应用到 WT/WT 移植物的连接处促进了移植物结合的形成，而乙烯生物合成抑制剂 AVG 的应用延迟了 WT/WT 移植物的移植物愈合，并且观察到的延迟在 WT/WT 移植物中不太明显。国际原子能机构移植物。这些结果表明，升高的生长素水平在国际原子能机构砧木与向上运输/扩散引起的接穗中生长素水平的增加相结合，增强了嫁接结合的形成，并且乙烯是生长素对嫁接影响的部分原因。我们的研究结果表明，可以通过使用转基因或基因编辑技术增加砧木中的生长素水平来提高嫁接成功率。