真核生物非編碼小RNA分子通過介導(dǎo)mRNA降解,、抑制蛋白質(zhì)翻譯和染色質(zhì)修飾負(fù)調(diào)控靶標(biāo)基因的表達(dá)。小RNA在植物的生長發(fā)育,、信號(hào)轉(zhuǎn)導(dǎo)以及生物和非生物脅迫反應(yīng)中起重要調(diào)控作用,。
植物基因組學(xué)國家重點(diǎn)實(shí)驗(yàn)室方榮祥院士研究組在對(duì)水稻MAIF1(miRNAs regulated and abiotic stress induced F-box gene) 基因的研究中發(fā)現(xiàn)：該基因受植物激素脫落酸(abscisic acid，ABA)和干旱,、高鹽等非生物脅迫因素的誘導(dǎo)啟動(dòng)表達(dá),，同時(shí)又受小RNA（siR441和siR446）的轉(zhuǎn)錄后調(diào)控。作為MAIF1的負(fù)調(diào)控子,，siR441和siR446的表達(dá)量受ABA和非生物脅迫抑制,。但是令人感到意外的是，其前體RNA的積累卻顯著增加了,。深入研究證明：siR441和siR446存在一個(gè)自我調(diào)控的過程,，即當(dāng)siR441和siR446的前體RNA的表達(dá)量升高時(shí)會(huì)形成一種自我配對(duì)現(xiàn)象，該配對(duì)影響了其被正確剪切,，使得成熟小RNA的量不升反降,。
這種自我調(diào)控的機(jī)制的闡明部分回答了一個(gè)尚未被普遍研究的科學(xué)問題，既作為負(fù)調(diào)控因子的小RNA自身是如何被調(diào)控的,。
該項(xiàng)研究結(jié)果于近日發(fā)表在《植物期刊》The Plant Journal (2011) 65, 820–828）雜志上,。（生物谷Bioon.com）
生物谷推薦原文出處：
The Plant Journal DOI： 10.1111/j.1365-313X.2010.04467.x
Small RNAs from MITE-derived stem-loop precursors regulate abscisic acid signaling and abiotic stress responses in rice
Yan, Yongsheng; Zhang, Yuman; Yang, Kun; Sun, Zongxiu; Fu, Yaping; Chen, Xiaoying; Fang, Rongxiang
Keywords:small RNA;miniature inverted‐\repeat transposable element;stem-loop precursor;abscisic acid and abiotic stresses;riceSummarySmall silencing RNAs (sRNAs) are non‐coding RNA regulators that negatively regulate gene expression by guiding mRNA degradation, translation repression or chromatin modification. Plant sRNAs play crucial roles in various developmental processes, hormone signaling, immune responses and adaptation to a variety of abiotic stresses. miR441 and miR446 were previously annotated as microRNAs (miRNAs) because their precursors can form typical stem‐loop structures, but are not considered as real miRNAs because of inconsistency with some ancillary criteria of the recent guidelines for annotation of plant miRNAs. We tentatively rename them small interfering (si)R441 and siR446, respectively, in this study. It has recently been shown that the precursors of siR441 and siR446 might originate from the miniature inverted‐\repeat transposable element (MITE) Stowaway1. In this report, we show that, in contrast with Dicer‐like (DCL)3‐ and RNA‐dependent RNA polymerase (RDR)2‐dependent MITE‐derived ra‐siRNAs, siR441 and siR446 are processed by OsDCL3a but independent of OsRDR2, indicating that siR441 and siR446 are generated from single‐stranded stem‐loop precursors. We also show that abscisic acid (ABA) and abiotic stresses downregulate the expression of siR441 and siR446 but, surprisingly, increase the accumulation of their precursors in rice plants, implying that processing of siRNA precursors is inhibited. We provide evidence to show that this defective processing is due to increased precursor accumulation per se, possibly by intermolecular self‐pairing of the processing intermediate sequences, thus hindering their normal processing. Functional examinations indicate that siR441 and siR446 are positive regulators of rice ABA signaling and tolerance to abiotic stress, possibly by regulating MAIF1 expression.
