论文摘要
Nitrogen is one of the most important constituents in the plant nutrition.Nitrogen cycle is a complex cycle in the plant system,involving many enzymes.Increasing the efficiency of these enzymes is one of the better ways to increase the nitrogen use efficiency of the plant system.In this regard ten candidate genes induced by low nitrogen stress were studied for their function in the nitrogen or related cycle in the plants（rice system） by overexpressing and silencing the candidate genes.T-DNA inserted mutants of the candidate genes were also considered for the study.Unfortunately overexpressed, silenced transgenic plants and mutant lines did not show any visible changes under the normal and stress conditions in the field and hydroponic culture.Promoter analysis indicated expression for some of the candidate genes in some specific tissues.Among the ten selected candidate genes only LOCOs03g02590（OsPEX11-1） was not studied in the rice earlier.Therefore,present work was concentrated on this particular gene,LOCOs03g02590（OsPEX11-1）.Peroxisome membrane protein（PEX11） is under attention from last more than ten years and much progresses about its function have been achieved in different species（fungi including yeast,human beings,rat and Arabidopsis） and it was confirmed to be involved in peroxisome biogenesis.But,till today no work has been carried out on this gene in a monocot species.Therefore present study is throwing light on the behavior of this gene family in one of the most cultivated staple food crop, rice.We showed that five putative PEX11 genes（OsPEX11-1～5） were present in the rice genome and each contained three conserved motifs.The PEX11 sequences from rice and other species can be classified into three major groups.Promoter analysis indicates that most of the cis elements in rice and Arabidopsis are similar,and protein sequence analysis in 16 different species having the specific PEX11 domain shows that Leucine is the most common amino acid among all the 20 amino acids.Among the five rice PEX11 genes, OsPEX11-2 and -3 are the most recently inserted in the genome.Expression profile and RT-PCR analysis suggested that the members of PEX11 family in rice had differential expression patterns:OsPEX11-1 and OsPEX11-4 had higher expression levels in leaf tissues than in the other tissues,OsPEX11-2 showed very low expression in all the tissues studied.OsPEX11-3 was expressed predominantly in endosperm and germinating seeds, and OsPEX11-5 was expressed in all the tissues investigated. We also observed that the rice PEX11 genes had differential expression patterns under different abiotic stresses like,abscisic acid（ABA）,hydrogen peroxide（H2O2） treatments,salt,drought,nitrogen and phosphorous stresses.OsPEX11-1 and OsPEX11-4 were induced by ABA,H2O2,salt and low nitrogen stress conditions.OsPEX11-3 was responsive to ABA and H2O2 treatments,and OsPEX11-5 was responsive to ABA,H2O2, and salt treatments.However,OsPEX11-2 had no response to any of the stresses.Our results suggest that the rice PEX11 genes are diversified not only in sequences but also in expression patterns under normal and various stress conditions.