| Degradation of nucleic acid has an important role in indicating and regulating the life cycle of cells.DNA degradation is usually known as the initiation of cell ageing and death,and as a way for the plant to recycle nutrients.Effective transcript turnover which is controlled by RNA degradation can regulate gene expression post-transcriptionally.Previous studies have shown that there is functional and structural diversity in different nucleases,and differences can be found in their regulatory mechanisms,conservative structures,and the biochemical processes they are involved in.And the amount of research in identification and functional mechanisms of nuclease in higher plants is far less than that in micro-organisms and animals.In the model organism,Arabidopsis,the structureal and functional classification of nucleases involved in the process of nucleic acid degradation,particularly of DNA degradation,has rarely been reported.In addition,the existed researches on the functions of proteins containing conserved nuclease domains indicate that conserved nuclease domains are able to catalyze phosphate bonds cleavage.Both nucleic acid and other compounds containing scissile phosphates can be used as the substrate of nuclease.And,in Arabidopsis,most nucleic acid degradation associated nuclease mutants or function defective mutants of proteins containing nuclease conserved domains exhibit growth deformities,and some biotic and abiotic stress resistance phenotype.This assay focuses on specific nucleic acid degradation function of nucleases and refers to thorough annotation to Arabidopsis genome and transcriptome.We predicted nucleases involved in DNA or RNA degradation and their expression pattern.Then we carried out some experiments to detect abiotic stress-induced expression and mutants response to abiotic stresses.We attempt to explore the relationship between nucleic acid degradation and abiotic stress conditions by doing those analyses.We identified 29 DNase genes and 31 RNase genes in the model plant,Arabidopsis thaliana.We have done some specific researches on the predicted DNases and RNases.(1)Through using bioinformatics web sites and softwares,we have collected the protein information of these genes and predicted their subcellular localizations.Results showed that RNase family members have a more extensive subcellular localization,like extracellular and mitochondria,while most DNases have acentralized localization of nucleus,cytoplasm and chloroplast.Further more,RNases have more various nuclease domains than DNases.(2)By phologenetic analysis on DNase and RNase family members,we found that the evolutionary relationships among family members are not close.(3)We analyzed the expression patterns of DNase and RNase family members using the Arabidopsis mRNA array.The results indicated that most nucleases,especially RNase family members,have a constitutive expression pattern.(4)Nuclease stress-induced expression analysis and phynotype identification of mutants implied that the expression of the majority of nuclease is subject to stress influence.Moreover,some nucleases’ function surely involved in plant’s response to abiotic stresses. |
