Table_5_Ozone and nitrogen dioxide regulate similar gene expression responses in Arabidopsis but natural variation in the extent of cell death is likely controlled by different genetic loci.xlsx

High doses of ozone (O3) and nitrogen dioxide (NO2) cause damage and cell death in plants. These two gases are among the most harmful air pollutants for ecosystems and therefore it is important to understand how plant resistance or sensitivity to these gases work at the molecular level and its genetic control. We compared transcriptome data from O3 and NO2 fumigations to other cell death related treatments, as well as individual marker gene transcript level in different Arabidopsis thaliana accessions. Our analysis revealed that O3 and NO2 trigger very similar gene expression responses that include genes involved in pathogen resistance, cell death and ethylene signaling. However, we also identified exceptions, for example RBOHF encoding a reactive oxygen species producing RESPIRATORY BURST OXIDASE PROTEIN F. This gene had increased transcript levels by O3 but decreased transcript levels by NO2, showing that plants can identify each of the gases separately and activate distinct signaling pathways. To understand the genetics, we conducted a genome wide association study (GWAS) on O3 and NO2 tolerance of natural Arabidopsis accessions. Sensitivity to both gases seem to be controlled by several independent small effect loci and we did not find an overlap in the significantly associated regions. Further characterization of the GWAS candidate loci identified new regulators of O3 and NO2 induced cell death including ABH1, a protein that functions in abscisic acid signaling, mRNA splicing and miRNA processing. The GWAS results will facilitate further characterization of the control of programmed cell death and differences between oxidative and nitrosative stress in plants.

高浓度臭氧（O3）与二氧化氮（NO2）会对植物造成损伤并引发细胞死亡。这两种气体是对生态系统危害最严重的空气污染物之一，因此解析植物对这类气体的抗性或敏感性的分子机制及其遗传调控机制具有重要意义。本研究将O3与NO2熏蒸处理后的转录组数据，与其他细胞死亡相关处理的转录组数据，以及不同拟南芥（Arabidopsis thaliana）生态型中的标记基因转录水平进行了对比分析。结果显示，O3与NO2诱导的基因表达响应高度相似，涉及病原物抗性、细胞死亡及乙烯信号通路相关基因。不过本研究也发现了例外情况：例如编码产生活性氧的呼吸爆发氧化酶蛋白F（RESPIRATORY BURST OXIDASE PROTEIN F）的基因RBOHF，其转录水平在O3处理下上调，却在NO2处理下下调，这表明植物能够分别识别这两种气体，并激活不同的信号通路。为解析相关遗传机制，本研究针对自然拟南芥生态型的O3与NO2耐受性开展了全基因组关联分析（GWAS）。研究发现，植物对这两种气体的敏感性似乎由多个独立的小效应位点调控，且二者的显著关联区域不存在重叠。对GWAS候选位点的进一步功能表征，鉴定出了调控O3与NO2诱导细胞死亡的新调控因子，其中包括ABH1——一种参与脱落酸信号通路、mRNA剪接及miRNA加工的蛋白质。本次GWAS研究结果将推动植物程序性细胞死亡调控机制，以及氧化应激与亚硝化应激差异的后续解析工作。