Oil Palm Fruit Abscission Zone Transcriptome

To determine the mechanisms of fleshy fruit abscission of the monocot oil palm (Elaeis guineensis Jacq.) compared with other abscission systems, we performed multi-scale comparative transcriptome analyses on fruit targeting the developing primary AZ and adjacent tissues. Combining between-tissue developmental comparisons with exogenous ethylene treatments, and naturally occurring abscission in the field, RNAseq analysis revealed a robust core set of 168 genes with differentially regulated expression, spatially associated with the ripe fruit AZ, and temporally restricted to the abscission timing. The expression of a set of candidate genes was validated by qRT-PCR in the fruit AZ of a natural oil palm variant with blocked fruit abscission, which provides evidence for their functions during abscission. Our results substantiate the conservation of gene function between dicot dry fruit dehiscence and monocot fleshy fruit abscission. The study also revealed major metabolic transitions occur in the AZ during abscission, including key senescence marker genes and transcriptional regulators, in addition to genes involved in nutrient recycling and reallocation, alternative routes for energy supply and adaptation to oxidative stress. The study provides the first reference transcriptome of a monocot fleshy fruit abscission zone and provides insight into the mechanisms underlying abscission by identifying key genes with functional roles and processes, including metabolic transitions, cell wall modifications, signalling, stress adaptations and transcriptional regulation, that occur during ripe fruit abscission of the monocot oil palm. The transcriptome data comprises an original reference and resource useful towards understanding the evolutionary basis of this fundamental plant process.

为解析单子叶植物油棕（Elaeis guineensis Jacq.）肉质果实脱落的分子机制，并与其他植物脱落系统开展对比研究，我们针对发育中的初级离区（abscission zone, AZ）及邻近组织的果实样本开展了多尺度比较转录组分析。结合组织间发育对比实验、外源乙烯处理实验以及田间自然脱落样本的分析，RNA测序（RNAseq）结果鉴定得到一套稳健的核心基因集，共包含168个基因，其表达呈差异调控模式，空间上定位于成熟果实离区，时间上则严格对应脱落发生时段。我们针对一株果实脱落受阻的天然油棕变异株，利用实时定量反转录聚合酶链反应（qRT-PCR）验证了其果实离区中部分候选基因的表达水平，这为这些基因在果实脱落过程中的功能提供了直接实验证据。本研究结果证实，双子叶植物干燥果实开裂与单子叶植物肉质果实脱落之间存在保守的基因功能机制。本研究同时发现，在果实脱落过程中，离区发生了显著的代谢重编程：除了参与养分循环与再分配、能量供应替代途径以及氧化应激适应的功能基因外，还包含关键的衰老标记基因与转录调控因子。本研究首次构建了单子叶植物肉质果实离区的参考转录组数据集，并通过鉴定油棕成熟果实脱落过程中涉及的关键功能基因与生物学过程——包括代谢重编程、细胞壁修饰、信号转导、逆境适应以及转录调控——深入解析了果实脱落的潜在分子机制。该转录组数据为理解这一基础植物生物学过程的进化起源提供了原创性参考资源与研究工具。