Pto-miR171b And Its Target Genes Against Heat Stress In Populus

mi RNA is a kind of endogenous non-coding single-strand small-molecule RNA in length of 20~24nucleotides,which regulates the expression of the target genes by complementary pairing manner.mi RNAs are widely present in plant genomes and involved in biological processes such as plant growth and development,and stress resistance.The research here analyzed the expression pattern of poplar Pto-mi R171 b under high temperature stress and resistance performance.Further,the inhibitory effect of Pto-mi R171 b on target genes was evaluated.The main results are as follows:(1)Pto-mi R171 b and target genes in response to heat stress in Populus tomentosaAfter high temperature treatment,the expression level of Pto-mi R171 b in Populus tomentosa TC1521 increased about 4.7 times as control.While,the expression of the five predicted target genes GRAS was reduced by about 13%~68%.All these indicated that Pto-mi R171 b regulation system is involved in the high temperature resistance process of plants.(2)Cloning and heat resistance of Pto-pri-mi R171 b and the target gene 5 in Populus tomentosaThe primary fragment of Pto-mi R171b(Pto-pri-mi R171b)and the target gene 5 were cloned and transformed into tobacco plants.Both the wild and the transgenic plants showed higher MDA content and proline content after heat treatment in comparison of that before treatment,while the chlorophyll content decreased.Comparably,the transgenic pto-Pri-mi R171 b tobacco plants had higher proline and chlorophyll content,and lower MDA content than the wild plants.While,the target gene 5 transgenic plants had higher MDA content,and lower proline and chlorophyll content than the wild plants after heat treatment.(3)Regulation of Pto-mi R171 b on the target gene expressionThe cleavage site of the target m RNAs by Pto-mi R171 b was anchored via RLM-5’RACE analysis,which was between the 7th and 8th base of the 5 ’end of Pto-mi R171 b.The Pto-pri-mi R171 b and the five target genes were cloned and assembled to the expression vectors.A tobacco transient expression test was conducted for the Pto-mi R171 b inhibitory effect on the target genes.The results showed that the expression level of the target gene gradually decreased along with the increase of bacterial concentration of Pto-pri-mi R171 b.The different target genes were partly inhibited,the target genes 1 and 7 were inhibited quickly and the target genes 2,6,and 8 were inhibited relatively slow.