College of Horticulture, Gansu Agricultural University, Lanzhou, 730070, China.
College of Bioengineering and Biotechnology, Tianshui Normal University, Tianshui, 741000, China.
Planta. 2023 Feb 5;257(3):48. doi: 10.1007/s00425-023-04086-3.
The decreased capacity of auxin-, CTK-, and BR-mediated cell division and cell enlargement pathways, combined with the enhanced capacity of GA and ETH-, JA-, ABA-, SA-mediated stress-resistant pathways were presumed to be the crucial reasons for the formation of spur-type 'Red Delicious' mutants. Vallee Spur', which exhibit short internodes and compact tree shape, is the fourth generation of the spur-type bud sport mutant of 'Red Delicious'. However, the underlying molecular mechanism of these properties remains unclear. Here, comparative phenotypic, full-length transcriptome and phytohormone analyses were performed between 'Red Delicious' (NSP) and 'Vallee Spur' (SP). The new shoot internode length of NSP was ˃ 1.53-fold higher than that of the SP mutant. Cytological analysis showed that the stem cells of the SP mutant were smaller and more tightly arranged relative to the NSP. By Iso-Seq, a total of 1426 differentially expressed genes (DEGs) were detected, including 808 upregulated and 618 downregulated genes in new shoot apex with 2 leaves of the SP mutant. Gene expressions involved in auxin, cytokinin (CTK), and brassinosteroid (BR) signal transduction were mostly downregulated in the SP mutant, whereas those involved in gibberellin (GA), ethylene (ETH), jasmonate (JA), ABA, and salicylic acid (SA) signal transduction were mostly upregulated. The overall thermogram analysis of hormone levels in the shoot apex carrying two leaves detected by LC-MS/MS absolute quantification showed that the levels of IAA-Asp, IAA, iP7G, OPDA, and 6-deoxyCS were significantly upregulated in the SP mutant, while the remaining 28 hormones were significantly downregulated. It is speculated that the decreased capacity of auxin, CTK, and BR-mediated cell division and cell enlargement pathways is crucial for the formation of the SP mutant. GA and stress-resistant pathways of ETH, JA, ABA, and SA also play vital roles in stem elongation. These results highlight the involvement of phytohormones in the formation of stem elongation occurring in 'Red Delicious' spur-type bud sport mutants and provide information for exploring its biological mechanism.
生长素、细胞分裂素和油菜素内酯介导的细胞分裂和细胞扩大途径的能力下降，加上赤霉素和乙烯、茉莉酸、脱落酸、水杨酸介导的应激抗性途径的能力增强，被认为是形成spur 型“红元帅”突变体的关键原因。Vallee Spur'，表现出短节间和紧凑的树形，是“红元帅”spur 型芽变突变体的第四代。然而，这些特性的潜在分子机制尚不清楚。在这里，对“红元帅”（NSP）和“Vallee Spur”（SP）之间进行了比较表型、全长转录组和植物激素分析。NSP 的新梢节间长度比 SP 突变体高˃1.53 倍。细胞学分析表明，SP 突变体的茎干细胞相对 NSP 更小且排列更紧密。通过 Iso-Seq，共检测到 1426 个差异表达基因（DEGs），其中 SP 突变体新梢顶2 叶中 808 个上调和 618 个下调基因。生长素、细胞分裂素（CTK）和油菜素内酯（BR）信号转导相关基因在 SP 突变体中大多下调，而赤霉素（GA）、乙烯（ETH）、茉莉酸（JA）、脱落酸（ABA）和水杨酸（SA）信号转导相关基因在 SP 突变体中大多上调。LC-MS/MS 绝对定量检测带 2 叶新梢顶激素水平的总热图分析表明，SP 突变体中 IAA-Asp、IAA、iP7G、OPDA 和 6-脱氧 CS 的水平显著上调，而其余 28 种激素的水平显著下调。推测生长素、细胞分裂素和油菜素内酯介导的细胞分裂和细胞扩大途径的能力下降是 SP 突变体形成的关键。赤霉素和 ETH、JA、ABA 和 SA 的应激抗性途径也在茎伸长中发挥重要作用。这些结果强调了植物激素在“红元帅”spur 型芽变突变体中茎伸长形成中的作用，并为探索其生物学机制提供了信息。
