Identification And Analysis Of MicroRNA Genes From Triticum Aestivum

MicroRNAs (miRNAs) are a class of endogenous small non-coding RNAs about 22nt long that present extensively in many species such as Caenorhabditis elegans, Drosophila melanogaster, Mus musculus, Homo sapiens and Arabidopsis thaliana et al, which play an important role in the development of various organisms. Several hundred microRNAs have been being experimentally identified and predicted by computational methods both in animals and plants. It will be difficult to identify the microRNAs using experimental approaches when they are low-expressed in organisms or ecpressed in particular stages. Some microRNAs are difficult to clone because of their characteristics including composition of their sequences or editing after transcription or methylation. Most endogen siRNAs and microRNAs are low-expressed that the signal they send is weak, so there are much obstacles to identify microRNAs using micro-arrays. Recently, identification of microRNA using bioinformation is gradually popular with the completion of genomic sequencing in human and many model organisms. Wheat is the secondly abundant foodstuff in the world (only after maize) and is one of the staple foods of man and animals. It is the commodity grain of high nutrition and economic value. Wheat is important in our country's foodstuff system. China is the biggest country in the wheat production which is an important part of the agricultural production. So it is important to study on the wheat's characteristics of anti-insect and anti-salt. It is recently reported that microRNAs are associated with every stages of plant's growth and development, so it's necessary to study on the microRNAs in wheat. The first step of studing on microRNAs is to find out as much as microRNAs and their targets.We search wheat genome and EST databases using bioinformation approaches to find microRNA candidates in order to, on the one hand, increase the wheat microRNA database so that people can do further research in regulation of genetic expression in wheat, on the other hand to study on the mode of action between microRNAs and their targets in wheat and the system of action between microRNAs and their targets in the whole plant system. There are almost all the microRNAs that are discovered and verified in miRBase database. We select all the plant microRNAs' mature sequences in miRBase database as model sequences to do the homology research and folding. Sequences that fit the standard we set are thought to be microRNA candidates, some of which are selected to do the RT-PCR to verify the expression. Then, we use miRU to find targets of these microRNA candidates and analyze the function and position and mode of action of their targets in order to predict the function of microRNAs in wheat and the whole plant system. The following is the summarization of our result:We totally discover 29 microRNAs candidates in wheat using homolog research in genome and EST database. Most of the microRNA candidates can be folded into typical hairpin struction of microRNA. The totally 29 microRNA candidates belongs to 22 microRNA families. Of all the wheat microRNA candidates, 4 are multicopy and 19 are single-copy. There are 20 EST sequences and 9 other sequences, 6 of which are selected to do RT-PCR. The RT-PCR result is 2 of the 6 have straps in all tissues and 2 have straps in some of tissues and 2 have no straps. All of these illustrate that some microRNA may have effect on all tissues of the same organism, but some may have effect on parts of tissues. We draw the conclution that microRNAs have important functions in the regulation of different stages of growth and development in plants.