摘 要: 落花落果是花、果实、种子从母体脱落的一种普遍存在的自然现象。发生器官脱落的区域为离区(abscission zone,AZ)。离区分化形成离层,离层与脱落息息相关。离层的发育和功能行使是多酶、多激素、多基因参与调控的复杂而精确的过程。落花落果不仅是作物栽培和育种中的典型农艺性状,而且是植物器官脱落的主要形式之一。减少植物落花落果或控制某些植物适度落花落果,提高作物和果蔬类植物的产量和品质,是人类在作物驯化上努力的目标。该文基于前人对植物器官脱落的生理生化和分子生物学机制的研究,主要从植物落花落果的细胞学基础、生理生化机制、遗传学规律、分子生物学和相关基因定位、转录组分析方面阐述落花落果分子机理,重点从落花落果的分子生物学和相关基因定位两个方面进行剖析落花落果的作用机制,以便为作物遗传育种研究提供理论指导。
关键词: 离层, 落花落果, 细胞学, 基因定位, 分子机制
中图分类号: Q943 文献标识码: A 文章编号: 1000-3142(2018)09-1234-14
Abstract: Falling flowers, fruits and seeds are the common natural phenomenons of plant organs that are detached from the mother plant. The organ exfoliation area is called as abscission zone (AZ). The abscission layer can be differentiated in abscission zone and has close relationship with shedding. The development and function of the abscission layer are controlled by many enzymes, many hormones, and many genes, which involve a complex and accurate process. Falling flowers and fruits are not only typical agronomic traits in crop cultivation and breeding, but also one of the major forms of plant shedding. Reducing the number of plant organs falling or controlling the proper shattering for increasing the yield and quality in some crops, fruits and vegetable plants have been the goal of crop domestication. Based on the previous studies on the physiological, biochemical and molecular biological mechanisms of plant organ abscission, this paper mainly reviewed the molecular mechanism of falling flowers and fruits from the aspects of cytology, physiological and biochemical mechanism, genetics, molecular biology, related gene mapping, and transcriptome analysis. Among them, molecular biology and related gene mapping were focused, which provided some guidance for crop genetics and breeding.
Key words: absciss layer, falling flowers and fruits, cytology, gene mapping, molecular mechanism
植物落花落果是花、果實、种子等脱离植株主体的一种广泛存在的自然现象。植物在正常生长发育过程中为适应逆境胁迫(如干旱、水淹、极端温度、元素N、B、Ca、Zn缺乏、病虫害等)或平衡自身生长水平减少累赘或扩散种子(繁殖体)时,一些器官会发生正常或不正常脱落。在正常脱落方面,叶的正常脱落保存了体内仅有的水分或减少细菌等病原感染(Patharkar & Walker, 2015);花果的正常脱落调节了植物本身源库关系和促进营养物质、矿物质合理分配。然而,自然界中很难避免不正常脱落带来的损失,如水稻和小麦落粒、棉花脱铃、大豆果荚脱落造成大量减产。在农业生产方面,对植物器官脱落进行合理调控,不仅可以有效利用土地资源,而且可以使作物达到高产、优质的效果。孙福东等(2016)报道在大豆叶面喷施植物生长调节剂DTA-6使大豆果荚离区Gm AC的表达量降低,果荚离区生理代谢被改变,大豆脱落率降低;Yuan & Carbaugh (2007)在柑橘和苹果采摘前喷施IAA(indole-3-acetic acid)和ETH(ethylene)阻断剂,防止水果在机械采摘前掉落。Lin et al (2012)在大豆、高粱等粮食作物驯化相关性状进行遗传解析中,借助分子标记等手段发现了一系列调控落粒性状的关键位点。分子标记育种和基因聚合育种是提高育种质量和效率的有效途径,对离层形成的生理和分子机制进行综述,为落花落果的机制研究和育种实践提供线索。