University of Tsukuba, Ibaraki, Japan.
BMC Plant Biol. 2010 Jun 16;10:111. doi: 10.1186/1471-2229-10-111.
Raphanusanin (Ra) is a light-induced growth inhibitor involved in the inhibition of hypocotyl growth in response to unilateral blue-light illumination in radish seedlings. Knowledge of the roles of Ra still remains elusive. To understand the roles of Ra and its functional coupling to light signalling, we constructed the Ra-induced gene library using the Suppression Subtractive Hybridisation (SSH) technique and present a comparative investigation of gene regulation in radish seedlings in response to short-term Ra and blue-light exposure.
The predicted gene ontology (GO) term revealed that 55% of the clones in the Ra-induced gene library were associated with genes involved in common defence mechanisms, including thirty four genes homologous to Arabidopsis genes implicated in R-gene-triggered resistance in the programmed cell death (PCD) pathway. Overall, the library was enriched with transporters, hydrolases, protein kinases, and signal transducers. The transcriptome analysis revealed that, among the fifty genes from various functional categories selected from 88 independent genes of the Ra-induced library, 44 genes were up-regulated and 4 were down-regulated. The comparative analysis showed that, among the transcriptional profiles of 33 highly Ra-inducible genes, 25 ESTs were commonly regulated by different intensities and duration of blue-light irradiation. The transcriptional profiles, coupled with the transcriptional regulation of early blue light, have provided the functional roles of many genes expected to be involved in the light-mediated defence mechanism.
This study is the first comprehensive survey of transcriptional regulation in response to Ra. The results described herein suggest a link between Ra and cellular defence and light signalling, and thereby contribute to further our understanding of how Ra is involved in light-mediated mechanisms of plant defence.
瑞香素（Ra）是一种光诱导生长抑制剂，参与萝卜幼苗单侧蓝光照射下抑制下胚轴生长的过程。然而，Ra 的作用机制仍然难以捉摸。为了深入了解 Ra 的作用及其与光信号转导的功能偶联，我们利用抑制性消减杂交（SSH）技术构建了 Ra 诱导基因文库，并对萝卜幼苗短期 Ra 和蓝光暴露的基因调控进行了比较研究。
预测的基因本体（GO）术语表明，Ra 诱导基因文库中的 55%克隆与参与共同防御机制的基因有关，其中包括 34 个与拟南芥基因同源的基因，这些基因涉及程序性细胞死亡（PCD）途径中 R 基因触发的抗性。总体而言，该文库富含转运蛋白、水解酶、蛋白激酶和信号转导器。转录组分析表明，在从 Ra 诱导文库的 88 个独立基因中选择的 50 个来自不同功能类别的基因中，有 44 个基因上调，4 个基因下调。比较分析表明，在 33 个高度 Ra 诱导的基因的转录谱中，25 个 ESTs 被不同强度和持续时间的蓝光照射共同调节。这些转录谱以及早期蓝光的转录调控，为许多预期参与光介导防御机制的基因的功能作用提供了依据。
本研究是首次对 Ra 响应的转录调控进行全面调查。研究结果表明 Ra 与细胞防御和光信号转导之间存在联系，从而有助于进一步了解 Ra 如何参与植物光介导的防御机制。
