萘乙酸（NAA）和2,4-二氯苯氧乙酸（2,4-D）在减少夜香树（Cestrum elegans）切花小花脱落方面的差异效应与其对Aux/IAA同源基因的差异激活有关。
Differential effects of NAA and 2,4-D in reducing floret abscission in cestrum (Cestrum elegans) cut flowers are associated with their differential activation of Aux/IAA homologous genes.
作者信息
Abebie Bekele, Lers Amnon, Philosoph-Hadas Sonia, Goren Raphael, Riov Joseph, Meir Shimon
机构信息
The Kennedy-Leigh Centre for Horticultural Research, The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Hebrew University of Jerusalem, Faculty of Agriculture, Rehovot 76100, Israel.
出版信息
Ann Bot. 2008 Jan;101(2):249-59. doi: 10.1093/aob/mcm115. Epub 2007 Jun 25.
BACKGROUND AND AIMS
A previous study showed that the relative effectiveness of 2,4-dichlorophenoxyacetic acid (2,4-D) compared with that of 1-naphthaleneacetic acid (NAA) in reducing floret bud abscission in cestrum (Cestrum elegans) cut flowers was due to its acropetal transport. The aim of the present study was to examine if the differential effect of these auxins on floret abscission is reflected in the expression of Aux/IAA genes in the floret abscission zone (AZ).
METHODS
cDNAs were isolated by PCR-based cloning from the floret AZ of auxin-treated cut flowers. The expression patterns of the cDNAs in various tissues and the effect of indole-3-acetic acid (IAA), applied with or without cycloheximide, on their expression in the floret AZ were examined by northern blot analysis. The regulation of transcript accumulation in the floret AZ in response to NAA or 2,4-D was measured by real-time PCR during auxin pulsing of cut flowers and vase life, concomitantly with floret abscission.
KEY RESULTS
Six isolated cDNAs were identified to represent Aux/IAA homologous genes, designated as Cestrum elegans (Ce)-IAA1 to Ce-IAA6. Four Ce-IAA genes were characterized as early auxin-responsive genes (ARGs), and two (Ce-IAA1 and Ce-IAA5) as late ARGs. Only Ce-IAA5 was AZ-specific in floret buds. A temporal regulation of Ce-IAA transcript levels in the floret AZ was found, with 2,4-D inducing higher expression levels than NAA in floret buds. These Ce-IAA expression levels were negatively correlated with floret abscission.
CONCLUSIONS
The differential transport characteristics of NAA and 2,4-D in cestrum cut flowers were reflected in differential activation of the Ce-IAA genes identified in the floret AZ. Therefore, Aux/IAA genes can be used as molecular markers to measure auxin activity, which reflects free auxin level in the AZ. Two of the identified genes, Ce-IAA1 and Ce-IAA5, may also have a regulatory role in abscission.
背景与目的
先前的一项研究表明，2,4-二氯苯氧乙酸（2,4-D）与1-萘乙酸（NAA）相比，在减少夜香树（Cestrum elegans）切花小花蕾脱落方面的相对有效性归因于其向顶运输。本研究的目的是检验这些生长素对小花脱落的差异效应是否反映在小花脱落区（AZ）中Aux/IAA基因的表达上。
方法
通过基于PCR的克隆从小花经生长素处理的切花的脱落区分离cDNA。通过Northern印迹分析检测cDNA在各种组织中的表达模式以及吲哚-3-乙酸（IAA）（添加或不添加环己酰亚胺）对其在小花脱落区表达的影响。在切花生长素脉冲处理和瓶插寿命期间，伴随着小花脱落，通过实时PCR测量小花脱落区中响应NAA或2,4-D的转录本积累的调节。
关键结果
鉴定出6个分离的cDNA代表Aux/IAA同源基因，命名为夜香树（Ce）-IAA1至Ce-IAA6。4个Ce-IAA基因被表征为早期生长素响应基因（ARG），2个（Ce-IAA1和Ce-IAA5）为晚期ARG。只有Ce-IAA5在小花蕾中是脱落区特异性的。在小花脱落区发现了Ce-IAA转录水平的时间调节，在小花蕾中2,4-D诱导的表达水平高于NAA。这些Ce-IAA表达水平与小花脱落呈负相关。
结论
NAA和2,4-D在夜香树切花中的差异运输特性反映在小花脱落区鉴定出的Ce-IAA基因的差异激活上。因此，Aux/IAA基因可作为测量生长素活性的分子标记，其反映了脱落区中的游离生长素水平。鉴定出的两个基因Ce-IAA1和Ce-IAA5也可能在脱落中起调节作用。
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