Global identification of potential gene biomarkers associated with ozone-induced foliar injury in rice seedling leaves by correlating their symptom severity with transcriptome profiling

Abstract

A combined approach of evaluating ozone (O3)-caused foliar injury symptom and global gene expression profiling was used to identify potential genes associated with severity of injury on leaves of O3 (200 ppb)-fumigated (1, 12, 24, 48, and 72 h) two-week-old rice (cv. Nipponbare) seedling. Foliar injuries were evaluated up to 72 h using both qualitative visual scale and quantitative RGB (red-green-blue) image analysis methods. The (R-G)/(R+G) was an optimal quantitative RGB parameter to assess foliar injury. Large-scale transcript profiling of leaves identified 270 genes linked with foliar injury. Genes were subjected to Pearson’s correlation test between their expression changes and O3-induced foliar injury changes (relative (R-G)/(R+G) parameters). Expression of 146 genes was found to increase with increased foliar severity up to 72 h, showing a positive, tight correlation between a subset of gene expression and commonly observed O3-triggerred symptom of foliar injury with correlation coefficient below -0.80. Of 146 genes, genes involved in metabolism (25%) formed a major functional category. Metabolic networks with identified metabolic genes provided insight into cellular responses such as photorespiration, biosynthesis of secondary metabolites, and detoxification. The O3 effect on these cellular responses has been previously reported based on physiological and biochemical studies, validating our approach used in this study to globally identify O3-responsive biomarkers tightly linked with foliar injury symptom. This study provides evidence for presence of large number of genes associated with foliar injury symptom than thought before, serving as a resource of potential biomarkers to study mechanisms of visible injury development by O3.DOI: http://dx.doi.org/10.3126/ijls.v6i1.6059