Beijing Academy of Forestry and Pomology Sciences, Beijing Academy of Agriculture and Forestry Sciences/Key Laboratory of Urban Agriculture (North China), Ministry of Agriculture, Beijing, 100093, People's Republic of China.
College of Horticulture Science and Engineering, Shandong Agricultural University, Tai'an, Shandong, 271018, People's Republic of China.
Plant Cell Rep. 2018 Dec;37(12):1693-1705. doi: 10.1007/s00299-018-2343-0. Epub 2018 Sep 4.
We confirmed the roles of auxin, CK, and strigolactones in apical dominance in peach and established a model of plant hormonal control of apical dominance in peach. Auxin, cytokinin, and strigolactone play important roles in apical dominance. In this study, we analyzed the effect of auxin and strigolactone on the expression of ATP/ADP isopentenyltransferase (IPT) genes (key cytokinin biosynthesis genes) and the regulation of apical dominance in peach. After decapitation, the expression levels of PpIPT1, PpIPT3, and PpIPT5a in nodal stems sharply increased. This observation is consistent with the changes in tZ-type and iP-type cytokinin levels in nodal stems and axillary buds observed after treatment; these changes are required to promote the outgrowth of axillary buds in peach. These results suggest that ATP/ADP PpIPT genes in nodal stems are key genes for cytokinin biosynthesis, as they promote the outgrowth of axillary buds. We also found that auxin and strigolactone inhibited the outgrowth of axillary buds. After decapitation, IAA treatment inhibited the expression of ATP/ADP PpIPTs in nodal stems to impede the increase in cytokinin levels. By contrast, after GR24 (GR24 strigolactone) treatment, the expression of ATP/ADP IPT genes and cytokinin levels still increased markedly, but the rate of increase in gene expression was markedly lower than that observed after decapitation in the absence of IAA (indole-3-acetic acid) treatment. In addition, GR24 inhibited basipetal auxin transport at the nodes (by limiting the expression of PpPIN1a in nodal stems), thereby inhibiting ATP/ADP PpIPT expression in nodal stems. Therefore, strigolactone inhibits the outgrowth of axillary buds in peach only when terminal buds are present.
我们证实了生长素、细胞分裂素和独脚金内酯在桃顶端优势中的作用，并建立了桃植物激素调控顶端优势的模型。生长素、细胞分裂素和独脚金内酯在顶端优势中发挥重要作用。在这项研究中，我们分析了生长素和独脚金内酯对 ATP/ADP 异戊烯基转移酶（IPT）基因（关键细胞分裂素合成基因）表达的影响以及对桃顶端优势的调控。去顶后，节间茎中 PpIPT1、PpIPT3 和 PpIPT5a 的表达水平急剧增加。这一观察结果与处理后节间茎和腋芽中 tZ 型和 iP 型细胞分裂素水平的变化一致；这些变化需要促进桃腋芽的生长。这些结果表明，节间茎中的 ATP/ADP PpIPT 基因是细胞分裂素合成的关键基因，因为它们促进了腋芽的生长。我们还发现生长素和独脚金内酯抑制了腋芽的生长。去顶后，IAA 处理抑制了节间茎中 ATP/ADP PpIPTs 的表达，从而阻碍了细胞分裂素水平的增加。相比之下，GR24（GR24 独脚金内酯）处理后，ATP/ADP IPT 基因的表达和细胞分裂素水平仍显著增加，但基因表达的增加速度明显低于去顶后无 IAA（吲哚-3-乙酸）处理时的增加速度。此外，GR24 抑制了节点处的基底向生长素运输（通过限制节点茎中 PpPIN1a 的表达），从而抑制了节点茎中 ATP/ADP PpIPT 的表达。因此，只有在顶芽存在的情况下，独脚金内酯才会抑制桃腋芽的生长。
