Expression Profiles Of Low Nitrogen Stressed Rice And QTL Analysis Of Low Nitrogen Tolerance

Nitrogen is a crucial plant macronutrient and is needed in the greatest amount of all mineral elements required by plants. It is a constituent of numerous important compounds, including amino acids, proteins, nucleic acids, chlorophyll and several plant hormones. The global use of N fertilizer increased dramatically in order to increase crop productivity, but the nitrogen use efficiency (NUE) is very low, which is even lower in rice fields than in other cereal crops, because of rapid N losses from volatilization and denitrification in the soil-floodwater system. The majority of N fertilizers was lost to the atmosphere or leached into groundwater, lakes and rivers, which causes increasingly severe pollutions to the environments. Thus, developing crops that are less dependent on the heavy application of N fertilizers is essential for the sustainability of agriculture.In this study we analyzed expression profile of rice seedlings at early stage of low N stress. The objective was to characterize the expression patterns of the genes representing a large segment of the rice genome in response to low N stress, with the hope to advance understanding of the physiological and biochemical processes underlying the response to low N stress. At the same time, we analyzed main-effects and digenic interactions of QTLs for seedling growth under low N stress and normal N conditions using a recombinant inbred line (RIL) population derived from an elite rice hybrid. The main results are as follows:1. Established the platform for gene expression profile study with cDNA microarray. All the procedures as making the chip, reverse transcription, probe labeling, hybridization, imagine scanning and data analysis were well established. The coefficients between the technical replications (dye-swap) are bigger than 0. 90.2. Using a microarray of 11, 494 rice ESTs representing 10, 422 unique genes, we analyzed the expression profiles of an indica rice cultivar Minghui 63 at seedling stage at 20 min, 1 hr and 2 hr after low N stress with the normal N as the control. A total of 471 ESTs were detected as responsive to low N stress in the root tissue with 115 ESTs showing up-regulation and 358 ESTs showing down-regulation.3. The analysis of expression profiles after low N stress identified following patterns: the genes involved in photosynthesis and energy metabolism were down-regulated rapidly; many of the genes involved in early responses to biotic and abiotic stresses were up-regulated while many other stress responsive genes were down-regulated; regulatory genes including transcription factors and ones involved in signal transduction were both...