College of Horticulture, Northwest A & F University, Yangling, Shaanxi, 712100, China.
College of Horticulture, Northwest A & F University, Yangling, Shaanxi, 712100, China.
Plant Physiol Biochem. 2018 Nov;132:579-589. doi: 10.1016/j.plaphy.2018.10.003. Epub 2018 Oct 9.
Most perennial fruit trees have an alternate bearing problem where a heavy fruit load is produced one year (ON year) but few flowers and fruits produced the next year (OFF year), resulting in a significant fluctuation in production. In the present study, comparative transcriptome analysis of terminal buds of apple (Malus domestica Borkh., cv. Nagafu No. 2) trees was conducted during the floral induction period in the ON and OFF years to identify the potential regulatory pathways controlling alternate bearing. A total of 1027 differentially expressed genes (DEGs), most of which were involved in secondary metabolism, sugar metabolism, plant hormone pathways, were identified. The analysis focused on differences in sugar content and hormone levels between the ON and OFF trees. Sucrose content, zeatin-riboside (ZR), and abscisic acid (ABA) levels were lower in ON-year buds than in OFF-year buds. ON buds also had elevated levels of gibberellins (GAs), with a higher expression of GA20 oxidase (GA20ox) and a significant lower level of RGA-like2 (RGL2). Expression analyses also revealed a significantly higher level of SQUAMOSA-PROMOTER BINDING PROTEIN-LIKE genes (MdSPL1, MdSPL6 and MdSPL12) transcripts levels in buds of OFF trees at 45 days after full bloom (DAFB). LEAFY (LFY) expression increased significantly prior to flower induction in OFF buds. These findings provide new information of the role of hormones in alternate bearing, as well as other processes, and provide new insights into the molecular mechanisms regulating alternate bearing in perennial fruit trees.
大多数多年生果树存在隔年结果现象，即在某一年份果实产量大（大年），而次年果实产量小（小年），导致产量波动较大。本研究以富士苹果（Malus domestica Borkh.，cv. Nagafu No. 2）为试材，在大年和小年的盛花诱导期，对其当年生新梢顶端休眠芽进行转录组分析，旨在鉴定控制苹果隔年结果的潜在调控途径。共鉴定到 1027 个差异表达基因（DEGs），这些基因主要参与了次生代谢、糖代谢和植物激素途径。研究重点关注了大年和小年休眠芽中糖含量和激素水平的差异。与小年休眠芽相比，大年休眠芽中蔗糖含量、玉米素核苷（ZR）和脱落酸（ABA）水平较低，赤霉素（GA）含量较高，GA20 氧化酶（GA20ox）表达量较高，RGA 样 2（RGL2）表达量较低。表达分析还表明，在盛花后 45 天，小年休眠芽中 SQUAMOSA-PROMOTER BINDING PROTEIN-LIKE 基因（MdSPL1、MdSPL6 和 MdSPL12）的转录水平显著较高。LFY 基因在小年休眠芽的花诱导前表达量显著增加。这些发现为激素在苹果隔年结果及其他过程中的作用提供了新信息，并为调控多年生果树隔年结果的分子机制提供了新的见解。
