Exogenous isoprene modulates gene expression in unstressed Arabidopsis thaliana plants

Isoprene is a well-studied volatile hemiterpene that protects plants from abiotic stress through mechanisms that are not fully understood. The antioxidant and membrane stabilizing potential of isoprene are the two most commonly invoked mechanisms. However, isoprene also affects phenylpropanoid metabolism, suggesting an additional role as a signaling molecule. In this study, microarray based gene expression profiling reveals widespread transcriptional reprogramming of Arabidopsis thaliana plants fumigated for 24 hrs with a physiologically relevant concentration of isoprene. Functional enrichment analysis of fumigated plants revealed enhanced heat- and light-stress-responsive processes in response to isoprene. Isoprene induced a network enriched in ERF and WRKY transcription factors, which may play a role in stress tolerance. The isoprene-induced upregulation of phenylpropanoid biosynthetic genes was specifically confirmed using quantitative reverse transcription polymerase chain reaction. These results support a role for isoprene as a signaling molecule, in addition to its possible roles as an antioxidant and membrane thermoprotectant. Plants were held at 23 °C for 24 hours and then held at 40 °C for 24 hours, either in the presence or absence of 20 PPM isoprene during the entire 48 hours. Leaf samples were taken at the end of both 24 hour treatment periods. Each of the 4 resulting conditions was replicated 3 times.

异戊二烯（Isoprene）是一种被广泛研究的挥发性半萜类物质，可通过尚未完全阐明的机制帮助植物抵御非生物胁迫。其抗氧化活性与膜稳定潜能是目前最常被提及的两种作用机制。但研究发现异戊二烯还可影响苯丙烷类代谢途径，提示其可能作为信号分子发挥额外功能。本研究通过基于基因芯片（microarray）的基因表达谱分析，发现经生理相关浓度异戊二烯熏蒸24小时的拟南芥（Arabidopsis thaliana）植株出现了广泛的转录重编程。对熏蒸植株的功能富集分析显示，异戊二烯处理可激活热胁迫与光胁迫响应相关的生物学过程。异戊二烯诱导形成了一个富含ERF转录因子（Ethylene Response Factor）与WRKY转录因子（WRKY Transcription Factor）的调控网络，这类转录因子可能在植物抗逆过程中发挥作用。本研究通过定量反转录聚合酶链式反应（qRT-PCR）特异性验证了异戊二烯诱导的苯丙烷类生物合成基因上调表达。上述结果支持异戊二烯除具备抗氧化剂与膜热保护剂的潜在功能外，还可作为信号分子发挥作用。实验中将植株先于23℃条件下培养24小时，随后在40℃环境下继续培养24小时；整个48小时的处理周期均设置添加20 ppm异戊二烯与不添加异戊二烯两组对照。在两个24小时处理阶段结束时分别采集叶片样本，最终得到4组实验条件，每组条件设置3次生物学重复。