The physiological network regulating sulfite detoxification in plants

以前，我们已经在植物中发现了亚硫酸盐氧化酶(SO)，克隆了其基因，并提供了关于其生物化学(原子结构、光谱和反应机理)、定位和功能的知识。亚硫酸盐的底物对植物细胞来说是高活性和高毒性的。亚硫酸盐可以在硫磺代谢过程中内源产生，也可以来自外部来源，如空气污染物二氧化硫。我们发现，在拟南芥和杨树中，SO对过量亚硫酸盐的解毒(安全阀功能)是必不可少的。本项目的目的是分析(A)SO-活性的转录和翻译后调节，以及(B)与额外的亚硫酸盐解毒机制的相互作用。对于转录调控，激活/失活SO启动子的特定转录因子特别重要：特定的DNA结合位点强烈表明受RAV1的控制。此外，还将研究SO蛋白的翻译后修饰(SUMO化、泛素化和磷酸化)。此外，mRNA深度测序揭示了植物中亚硫酸盐的第二种解毒机制：质外体过氧化物酶，也是从Pfan z和他的同事(1990)的工作中得知的。SO2诱导的质外体过氧化物酶的表达表明，质外体和共生体的解毒机制是独立的。我们已经做了第一次本地化实验，并获得了与底物愈创木酚和亚硫酸盐进行酶反应的第一批初步数据。现在，我们将从分子、细胞生物学和生化水平(亚硫酸盐解毒的反应机制)对质外体过氧化物酶进行研究，并计划研究这些质外体过氧化物酶的重要性及其与过氧化体SO的共同调节。此外，我们打算在自然栖息地和受控熏蒸实验中研究植物对二氧化硫水平增加的适应。我们计划在火山岛(意大利风沙群岛)收集植物材料，该岛以SO2-浓度闻名，位于L L-1级。我们想要回答的问题是，植物对自然环境中较高的SO2-浓度有何反应。我们是否发现，植物对SO2的长期适应在自然界中是通过更高的SO蛋白含量(转录或转录后修饰)实现的，还是通过适应的翻译后调节实现的？

Previously, we have discovered the enzyme sulfite oxidase (SO) in plants, cloned its gene, and provided knowledge about its biochemistry (atomic structure, spectroscopy, and reaction mechanism), localization and function. The substrate of SO - sulfite - is highly reactive and highly toxic for the plant cell. Sulfite can be produced endogenously during sulfur metabolism and can also derive from external sources like the air pollutant sulfur dioxide. We showed that SO is essential for detoxifying excessive amounts of sulfite (safety-valve function) in Arabidopsis and poplar. The aim of the present project is to analyze (a) the transcriptional and posttranslational regulation of SO-activity and (b) the interaction with an additional sulfite detoxification mechanism. For transcriptional regulation specific transcription factors for activation/inactivation of the SO promoter are of particular importance: specific DNA-binding-sites strongly suggest a control by RAV1. Moreover, posttranslational modifications of SO protein (SUMOylation, ubiquitinilation and phosphorylation) will be studied. Moreover, mRNA deep-sequencing revealed a second sulfite detoxification mechanism in plants: Apoplastic peroxidase, also known from work of Pfanz and colleagues (1990). Induction of the apoplastic peroxidases by SO2 in SO-knock out plants indicates independent apoplastic and symplastic detoxification mechanisms. We have done first localization experiments and have first preliminary data of the enzymatic reaction with the substrates guajacol and sulfite. Now, we will to investigate the apoplastic peroxidases on molecular, cell-biological and biochemical level (reaction mechanism for sulfite detoxification) and plan to study the importance of these apoplastic peroxidases and their co-regulation with peroxisomal SO. In addition, we intend to study plant adaptations to increased levels of SO2 both, in natural habitats and in controlled fumigation experiments. We plan to collect plant material at Volcano Island (Aeolian Archipelago, Italy) known for SO2-concentration in the µL L-1-level. We want to answer the question, how do plants react to higher SO2-concentrations in natural environments. Do we find a long-term adaptation of plants to SO2 achieved in nature by higher SO protein amounts (transcriptional or post-transcriptional modification) or by an adapted post-translational regulation?