Katz Ehud, Riov Joseph, Weiss David, Goldschmidt Eliezer E
The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, PO Box 12, Rehovot 76100, Israel.
J Exp Bot. 2005 May;56(415):1359-67. doi: 10.1093/jxb/eri137. Epub 2005 Mar 14.
Although leaves and other vegetative tissues are generally considered as non-climacteric, citrus leaves show a climacteric system II behaviour after detachment. Upon harvest, young, fully expanded 'Valencia' orange (Citrus sinensis) leaves ( approximately 60-d-old) exhibited two phases of ethylene production. The first phase, up to 6 d after detachment, was characterized by a low and constant ethylene production (system I pathway), associated with a constitutive expression of ACC synthase 2 (CsACS2), CsERS1, and CsETR1. ACC synthase 1 (CsACS1) was not expressed during this phase and autoinhibition of ethylene production was apparent following treatment with exogenous ethylene or propylene. The second phase, 7-12 d after detachment, was characterized by a climacteric rise in ethylene production, preceded by the induction of CsACS1 and ACC oxidase 1 (CsACO1) gene expression in the system II pathway. This induction was accelerated and augmented by exogenous ethylene or propylene, indicating an autocatalytic system II ethylene biosynthesis. Mature leaves (6-8-months-old) behaved similarly, except that the climacteric peak in ethylene production occurred earlier (day 5). Young and mature leaves varied in the timing of the climacteric ethylene rise and CsACS1 and CsACO1 induction. The two phases of ethylene production, system I and system II, were also detected in wounded leaf discs of both young and mature leaves. The first phase peaked 15 min after excision and the second phase peaked after 6 h.
尽管叶片和其他营养组织通常被认为是非跃变型的，但柑橘叶片在脱离植株后表现出跃变型系统II的行为。采收时，幼嫩、完全展开的‘伏令夏橙’（Citrus sinensis）叶片（约60日龄）表现出两个乙烯生成阶段。第一阶段，在脱离植株后的6天内，其特征是乙烯生成量低且恒定（系统I途径），这与ACC合酶2（CsACS2）、CsERS1和CsETR1的组成型表达相关。在此阶段，ACC合酶1（CsACS1）不表达，用外源乙烯或丙烯处理后，乙烯生成的自抑制作用明显。第二阶段，在脱离植株后的7 - 12天，其特征是乙烯生成出现跃变高峰，在此之前系统II途径中CsACS1和ACC氧化酶1（CsACO1）基因表达被诱导。外源乙烯或丙烯加速并增强了这种诱导作用，表明存在自催化的系统II乙烯生物合成。成熟叶片（6 - 8月龄）表现类似，只是乙烯生成的跃变高峰出现得更早（第5天）。幼叶和成熟叶在跃变乙烯升高以及CsACS1和CsACO1诱导的时间上有所不同。在幼叶和成熟叶的受伤叶圆片中也检测到了乙烯生成的两个阶段，即系统I和系统II。第一阶段在切除后15分钟达到峰值，第二阶段在6小时后达到峰值。
