Defferential Expression Of The Genes Associated With Allelopathic Effect In Rice On The Target Weeds Mediated By Different Nitrogen Supplies

Allelopathy is the phenomenon that effects of one plant on other plants through the release of chemical compounds into the environment, which has been considered an environment friendly approach to control weed in near future agriculture.Previous studies indicated that plant allelopathy increased under environmental stresses including nutrient starvation. To understand the mechanism, the investigation was conducted to detect the related gene expression profiles in allelopathic rice accession PI312777 exposed to lower nitrogen supply using suppression subtractive hybridization (SSH) method . A total of 35 ESTs from SSH-cDNA library were sequenced, and all of the sequences of inserted fragments were analyzed with the aid of bioinformatics. Twenty-four genes were sorted into five groups such as primary metabolism, phenol allelochemical synthesis, plant growth and cell cycle regulation, stress resistance and signal transduction, protein synthesis and degradation, which were involved in the pathways of allelochemical synthesis and stress defense in rice.Based on the result obtained from SSH analysis, the expression levels of the two up-regulated genes coding for PAL and cytochrome P450 in allelopathic rice PI312777 were compared with those in its counterpart Lemont by real-time fluorescent quantitative polymerase chain reaction (FQ-PCR) simultaneously to further confirm the SSH results and understand their expression patterns in different rice accessions in response to lower nitrogen treatment. The results indicated that the gene expression levels of PAL and cytochrome P450 were all increased in the two rice accessions when exposed to lower nitrogen supply. But the expression levels of the two genes encoding PAL and P450 in allelopathic rice PI312777 was higher than that in its counterpart Lemont. It was indicated that the relative expression level of PAL was increased by 11.38, 4.83 and 3.57 times in the root of PI312777, while 1.15, 2.74, and 2.94 folds in that of Lemont, respectively at three different time courses of the rice seedlings induced by lower nitrogen treatment for 1, 3, 7 days, when compared with control by normal nutrient condition. The same tendency was found in relative expression level of the gene encoding cytochrome P450. These findings suggested that the stronger ability of allelopathic rice in the suppression on the target weeds, especially in lower nitrogen supply in the mixture system, might be attributed to the stronger activation of the genes associated with the key enzymes involving in de novo synthesis of allelochemicals in time, Which is an intricate biochemical network involving stress resistance, cell cycle and growth regulation as well as signal transduction in plant defense response.