Gene Expression in Response to excess Copper Stress in Rice Leaves

Gene expression in response to Cu stress in rice leaves was quantified using DNA microarray (Agilent 22K Rice Oligo Microarray) and real-time PCR technology. Rice plants were grown in hydroponic solutions containing 0.3 (control), 10, 45 or 130 µM of CuCl2, and Cu accumulation and photosynthesis inhibition were observed in leaves within 1 day of the start of treatment. Microarray analysis flagged 305 Cu-responsive genes, and their expression profile showed that a large proportion of general and defense stress response genes are up-regulated under excess Cu conditions, whereas photosynthesis and transport-related genes are down-regulated. The Cu sensitivity of each Cu-responsive gene was estimated by the median effective concentration value (EC50) and the range of fold-changes (F) under the highest (130 µM) Cu conditions (|log2F|130). Defense-related genes involved in phytoalexin and lignin biosynthesis were the most sensitive to Cu. Our results indicate that plant management of abiotic and pathogen stresses has overlapping components, possibly including signal transduction. Keywords: dose response, stress response Rice plants were treated with hydroponic solutions containing 10 µM, 45 µM, or 130 µM CuCl2. Treatment with the standard rice hydroponic solution containing 0.3 µM CuCl2 was performed simultaneously as a control. Each experiment was triplicated. Thus, 9 array chips were used.