中文摘要：

MicroRNA（miRNA）是一类在生物体内普遍存在的非编码、长度约为21 nt的小RNA分子,一般由内源基因编码,RNA聚合酶Ⅱ转录后,经过Dicer-Like酶等一系列的蛋白复合物将pre-miRNA（precursor miRNA）剪切成成熟miRNA,在转录及转录后水平介导靶mRNA转录沉默、降解或翻译抑制来调控基因的表达,是真核细胞基因表达的重要调控因子。第一个miRNA是在秀丽隐杆线虫（C.elegans）中发现的lin-4,与lin-14 mRNA 3′UTR的碱基序列部分互补,降解lin-14,从而抑制lin-14的表达。lin-4对靶基因lin-14的调控与线虫的生长发育密切相关。而第一个发现的植物miRNA是拟南芥mi R171,它靶向剪切编码基因Scarecrow-Like（SCL）家族的mRNA,调控其基因的表达,进而影响植物的生长发育。植物部分miRNA,如mi R156—mi R408在各植物物种中相对保守,而mi R408以后的miRNA具有物种特异性。植物在生长过程中会遭遇诸多不可预知（如同盐碱、干旱、重金属以及害虫和病原菌的侵扰等）的环境胁迫。固着生长的特性使得植物不能像动物那样通过移动来避免不利环境的影响,因此,需要自身特殊机制来应对这些环境胁迫。植物在长期逆境中已进化出极为精细复杂的生理和分子机制。miRNA与它作用的靶基因是响应环境胁迫的主要调控因子。miRNA参与了植物的生长发育、信号转导、蛋白质降解、营养胁迫、抗病原菌的入侵以及适应高盐和干旱等逆境胁迫过程,对于调节内源抗性基因表达具有一定意义。目前通过高通量测序、实时定量PCR检测和转基因等技术已经发现了很多与环境胁迫相关的miRNA,它们在逆境胁迫下的表达呈现显著差异性;miRNA的过表达植株经逆境胁迫处理可能表现出一定的抗逆或敏感性。同一家族的miRNA不同成员在响应环境胁迫时具有物种特异性。新疆地区是典型的大陆性干旱气候,降水量少,盐碱荒漠化地区多。?

英文摘要：

MicroRNA（miRNA） is an extensive class of non-coding and small molecularRNA with length about 21 nt. It is encoded by the endogenous gene and transcribed byRNA polymerase II and the precursor miRNA is processed into mature miRNA by Dicer-Like and a series of the protein complexes. miRNA mainly regulates its targets at the level of post-transcription mediated degradation of target mRNA or translation inhibition. miRNA is an important regulator of gene expression in eukaryotic cells. Lin-4 is the first animal miRNA discovered in Caenorhabditis elegans（C. elegans）. It is essential for the growth and development of C. elegans by negative controlling the expression level of target gene lin-14 with partial complementarity to lin-14 mRNA in the 3′untranslated region（UTR）, causing the degradation of lin-14 gene and thus inhibiting the expression of lin-14 gene. Arabidopsis mi R171 is discovered as the first miRNA in plant, which targets mRNA of Scarecrow-Like（SCL） family, and thus mi R171 can affect plant growth and development by negative regulating target gene expression. Plant partial miRNAs（from mi R156 to mi R408） are relatively conserved among different species and other miRNAs after mi R408 are species-specific. Plants will encounter all kinds of unpredictably environmental stresses（salinity, drought, heavy metal, pest and pathogen infection）, because of plant sessile growth, no moving to avoid the adversely environmental effects like animals. Therefore, it is necessary for plants to cope with these stresses with their special mechanisms. Actually, plants grown chronically in the stressed environments have evolved highly complicated and delicate physiological and molecular mechanisms. Studies have showed that miRNA and its target genes are the main regulatory factors in response to various stresses. miRNAs play important roles in regulating the expression of endogenous resistance genes by involving in plant growth and development, signal transduction, protein degradation, nutrient deficien