Genetic Expression Analysis Of Young Leaves Of Maize Inbred Lines Mo17 And Huangzaosi Under Low Nitrate Treatment

Maize is so important just as food, animal feeds and biotic fuel in the worldwide. To satisfy the addition population day after day, most fertilizer is used. Associated with the increase of crop production is the serious problem of pollution of environment resulting from intensification of the use of nitrogen fertilizers in agriculture. The heavy reliance on fertilization increase for improving crop yield is associated with more pressures on environment protection, low cost-efficiency and sustainable agriculture development. This situation is currently very serious in developing countries like China. The development of plant varieties with high nitrogen use efficiency from diverse germplasm is the best economic strategy to solve this problem. Some efforts have been focused on genetic dissection of plant nitrogen utilization by tradition research method. Although these research results have provided valuable information to guide the manipulation of desirable genes through breeding to some extent, the understanding of the molecular basis of plant responses to nitrogen is still limited in part, due to the complex properties and the involvement of numerous genes for nitrogen uptake and assimilation. Nitrogen is the most important macronutrient and nitrate is the main inorganic nitrogen for maize growth and development because it is dry land crop. Investigating the molecular basis of maize response to nitrate is fundamental to facilitate to the improvement of nitrogen use efficiency in maize.In this study, two key maize inbred lines come from Tangsansipingto' group and 'Lancaster' group, exhibiting significant difference responding to nitrogen according Mo17 and Huangzaosi, are grown in nutrient solution with nitrate as the sole source of nitrogen. Control plants receive chloride. Leaf samples are collected 20 days(ds) after treatment. Whole-genome transcription profiling of leaf tissue for these two inbred lines is analyzed using the gene chip. Results are showed as follows:1. The number of genes induced in response to nitrate treatment in Mo 17 is significantly bigger than that in Huangzaosi. Results show that 2,451 genes in Mo 17 and 2,173 genes in Huangzaosi are up-regulated by low nitrate treatment. Using a cutoff value of 2, the number is 620 in Mo 17 and 197 in Huangzaosi. Which may be account to Mo 17 is more sensitive to nitrogen than Huangzaosi. 2. Genes directly involved in nitrate metabolism like nitrite reductase(NiR), ferredoxin (Fdâ…¥) and nitrate transportation protein(Nrt) show small response after low nitrate treatment for a long time. The signal ratio of nitrate reductase(NR) is no change in both Mo 17 and Huangzaosi between experiment and control. Signal ratio of nitrite reductase(NiR) is 1.4 in Mo 17 and no change in Huangzaosi. Ferredoxin (Fdâ…¥) with signal ratio 1.2 in Mo 17 and 1.1 in Huangzaosi are detected. All those results may be related to the rapid and transient of nitrate induction.3. Genes coding just as early light-inducible protein (ELIP), Methyltransferases, glucosidase and so on which are not directly involved in nitrate metabolism show strong responses to low nitrate. Signal ratio of ELIP in Mo 17 is -4 and -2.9 in Huangzaosi after treated with low nitrate. For glucosidase, the signal ratio is 3.5 in Mo 17 and 3 in Huangzaosi. The signal value is 1637.1/165.5 in Mo 17 between experiment and control. In Huangzaosi it is 3737.6/476.7 between experiment and control.4. Determination of chlorophyll content and agronomic characters investigations as well as leaf area show that density of nitrate supplies for Mo 17 and Huangzaosi and so on key inbred lines early at the seedling stage is 0.015mol/L.But under this density, corn nitrogen using efficiency need to be further studying.5. Additionally, some novel genes just as ezma: 12507, mir3 and ezma: 14277 with unknown proteins show strong induction are found under low nitrate treatment. These genes in Mo 17 affected by the low nitrate treatment show stronger induction than that in Huangzaosi, which may be relation to that Mo 17 is more sensitive to low nitrate than Huangzaosi.These results suggest that genes indirectly involved in nitrogen (N) uptake and assimilation are important during the maize lifecycle under nitrate treatment for a long time and will be very useful to further our understanding of genetic response mechanisms and to promote variety improvement for nitrogen use efficiency in maize.