Over-expression of miR172 causes loss of spikelet determinacy and floral organ abnormalities in rice (Oryza sativa)
Over-expression of miR172 causes loss of spikelet determinacy and floral organ abnormalities in rice (Oryza sativa)
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DOI：
10.1186/1471-2229-9-149
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发表时间：
2009-12-17
影响因子：
5.3
通讯作者：
Helliwell, Chris A.
中科院分区：
文献类型：
--
作者：
Zhu, Qian-Hao;Upadhyaya, Narayana M.;Helliwell, Chris A.
背景：microRNAs（miRNAs）对基因表达的调控在植物的许多发育和生理过程中起着至关重要的作用。miRNA通过mRNA切割或翻译抑制来抑制其靶基因的表达。在水稻中已经鉴定出数十个miRNA家族，其中21个在水稻和拟南芥中是保守的。miR 172是一个保守的miRNA家族，在拟南芥和玉米中调控APETALA 2（AP 2）样转录因子的表达。水稻基因组编码5个AP 2样基因，预测是miR 172的靶基因。为了确定这些水稻AP 2-like基因是否受miR 172调控并研究靶基因的功能，我们研究了miR 172家族的两个成员过表达对水稻植株发育的影响。结果：miR 172表达分析表明，它在营养生长后期和发育中的穗中表达最高。对三个miR 172靶标的表达分析表明，SUPERNUMERARY BRACT（SNB）和Os 03 g60430在发育中的穗中具有高表达。尽管通过5'cDNA末端快速扩增（RACE）检测到miR 172介导的SNB切割，但miR 172的表达与其靶点的表达不呈负相关。miR 172 b基因在水稻中的过量表达延缓了小穗分生组织向花分生组织的转变，导致花和种子发育缺陷，包括花器官数量和特性的改变、育性降低和种子重量减少。过表达miR 172 b的植物不仅表型模仿SNB的T-DNA插入突变体，而且还表现出在SNB突变体中未观察到的小花发育的额外缺陷。结论：miR 172 b过表达的表型表明，miR 172 b抑制SNB和至少一个miR 172的靶基因Os 03 g60430的表达，这表明其他AP 2类基因在水稻小花发育中的作用。miR 172和AP 2-like基因在水稻中的表达模式存在重叠，二者的表达量没有表现出明显的负相关。在miR 172 b过表达植物中，AP 2样miR 172靶mRNA的表达没有均匀的降低。这些观察结果与miR 172通过翻译抑制发挥功能或与AP 2样基因的表达受负反馈环调节一致。
Background: Regulation of gene expression by microRNAs (miRNAs) plays a crucial role in many developmental and physiological processes in plants. miRNAs act to repress expression of their target genes via mRNA cleavage or translational repression. Dozens of miRNA families have been identified in rice, 21 of which are conserved between rice and Arabidopsis. miR172 is a conserved miRNA family which has been shown to regulate expression of APETALA2 (AP2)-like transcription factors in Arabidopsis and maize. The rice genome encodes five AP2-like genes predicted to be targets of miR172. To determine whether these rice AP2-like genes are regulated by miR172 and investigate the function of the target genes, we studied the effect of over-expressing two members of the miR172 family on rice plant development.Results: Analysis of miR172 expression showed that it is most highly expressed in late vegetative stages and developing panicles. Analyses of expression of three miR172 targets showed that SUPERNUMERARY BRACT (SNB) and Os03g60430 have high expression in developing panicles. Expression of miR172 was not inversely correlated with expression of its targets although miR172-mediated cleavage of SNB was detected by 5' rapid amplification of cDNA ends (RACE). Overexpression of miR172b in rice delayed the transition from spikelet meristem to floral meristem, and resulted in floral and seed developmental defects, including changes to the number and identity of floral organs, lower fertility and reduced seed weight. Plants over-expressing miR172b not only phenocopied the T-DNA insertion mutant of SNB but showed additional defects in floret development not seen in the snb mutant. However SNB expression was not reduced in the miR172b over-expression plants.Conclusions: The phenotypes resulting from over-expression of miR172b suggests it represses SNB and at least one of the other miR172 targets, most likely Os03g60430, indicating roles for other AP2-like genes in rice floret development. miR172 and the AP2-like genes had overlapping expression patterns in rice and their expression did not show an obvious negative correlation. There was not a uniform decrease in the expression of the AP2-like miR172 target mRNAs in the miR172b over-expression plants. These observations are consistent with miR172 functioning via translational repression or with expression of the AP2-like genes being regulated by a negative feedback loop.