INSIGHTS INTO FLOODING TOLERANCE OF SAG12:ipt ARABIDOPSIS PLANTS THROUGH TRANSCRIPTOME ANALYSES

¹ USDA-ARS-Soil Drainage Research Unit, Columbus, OH 43210. USA

² The Institute for Genomic Research, Rockville, MD 20850. USA

³ Department of Horticulture and Crop Science, The Ohio State University, Columbus, OH 43210. USA

⁴ USDA-ARS National Forage Seed Production Research Center, Corvallis, OR 97331, USA

Transgenic Arabidopsis plants containing the SAG12:ipt autoregulated cytokinin production remain greener and produce more biomass and seeds than wild-type (WT) plants under flooding stress. Flooding induces a large increase in ipt transcript abundance in SAG12:ipt (IPT) plants which is accompanied by increased cytokinin accumulation. To profile changes in gene expression that contribute to flooding tolerance, whole genome DNA microarray analysis representing the more than 27,000 genes encoded in the Arabidopsis nuclear, chloroplast and mitochondrial genomes was conducted at specific times during a 5-day period of non-flooded control, waterlogging and complete submergence. Average linkage hierarchical clustering using Euclidean distance metric revealed distinct patterns of gene expression in the three treatments. Under flooding stresses, genes of photosynthesis and energy utilization pathways expressed 2- to 4-fold more in the tolerant IPT plants than in WT plants suggesting that flooding tolerance mechanisms involve both energy production and utilization. A number of transcription regulators and genes of signaling pathways were induced specifically in flooded IPT plants. Comprehensive analysis of transcriptional changes associated with cytokinin-induced flooding stress tolerance will be reported.