Rice Microrna Expression Of Transformed Plants For Phenotypic And Functional Analysis

MicroRNAs are a class of length of 21~23 nt, non-codding, and small molecule RNA that play very important roles in the development of plants and animals. As a class of regulative nucleic acid molecules, microRNAs recognize and negatively regulate their targets. In the present study, 10 rice microRNAs, including Os-miR390, Os-miR393, Os-miR394, Os-miR396, Os-miR397, Os-miR398, Os-miR435, Os-miR440, Os-miR441 and Os-miR1, were selected. The putative target genes of these 10 microRNAs were CSD(Cu/Zn Surperoxide dismutase), F-box protein, GRF(Growth regulational factor), transcriptional factors and some unknown proteins, etc..The main results were as following:1. The precursor DNA of the 4 microRNAs (Os-miR390, Os-miR397, Os-miR398, Os-miR440) were successfully cloned from rice genomic DNA and their expression vectors under the Ubiquitin I constitutive promoter constructed.2. We got the transgenic rice lines over-expressing Os-miR398, Os-miR397, Os-miR390, Os-miR394, Os-miR435, Os-miR441, respectively.3. We inverstigated detailed functions of Os-miR398 in the responses to stresses. MicroRNA398 targets two Cu/Zn superoxide dismutases (CSD1 and CSD2) in arabidopsis thaliana. Here we provided further evidence that rice microRNA 398 (Os-miR398)-mediated responses to abiotic and biotic stresses were also through regulating the expression of its target genes, CSD1 and CSD2, and thus controlled cellular react oxygen species (ROS) levels. Os-miR398 was expressed in all tissues examined, but higher expression was characterized especially in the young tissues. Both abiotic and biotic stresses used in the present study significantly inhibited the Os-miR398 expression and stimulated the expression of CSD1 and CSD2. The effects of environmental stresses on the expression of both Os-miR398 and CSDs were reversible. Furthermore, plant hormone ethylene also inhibited the Os-miR398 expression and stimulated the expression of CSD1 and CSD2. Transgenic rice lines which over-expressed Os-miR398 had a lower expression of CSDs and were more sensitive to Cu2+ treatments. Whereas, transgenic rice lines which over-expressed miR398-resistant form of CSD2 showed much more tolerant to high salinity than non-transgenic rice. It was suggested that the Os-miR398 regulate the responses of rice to wide range of environmental stresses and to ethylene and exert its roles through mediating CSDs expression and thus cellular ROS levels.