Wu Miin-Feng, Tian Qing, Reed Jason W
University of North Carolina at Chapel Hill, Department of Biology, CB #3280, Coker Hall, Chapel Hill, NC 27599-3280, USA.
Development. 2006 Nov;133(21):4211-8. doi: 10.1242/dev.02602. Epub 2006 Oct 4.
In flowering plants, diploid sporophytic tissues in ovules and anthers support meiosis and subsequent haploid gametophyte development. These analogous reproductive functions suggest that common mechanisms may regulate ovule and anther development. Two Arabidopsis Auxin Response Factors, ARF6 and ARF8, regulate gynoecium and stamen development in immature flowers. Wild-type pollen grew poorly in arf6 arf8 gynoecia, correlating with ARF6 and ARF8 expression in style and transmitting tract. ARF6 and ARF8 transcripts are cleavage targets of the microRNA miR167, and overexpressing miR167 mimicked arf6 arf8 phenotypes. Mutations in the miR167 target sites of ARF6 or ARF8 caused ectopic expression of these genes in domains of both ovules and anthers where miR167 was normally present. As a result, ovule integuments had arrested growth, and anthers grew abnormally and failed to release pollen. Thus, miR167 is essential for correct patterning of gene expression, and for fertility of both ovules and anthers. The essential patterning function of miR167 contrasts with cases from animals in which miRNAs reinforce or maintain transcriptionally established gene expression patterns.
在开花植物中，胚珠和花药中的二倍体孢子体组织支持减数分裂及随后的单倍体配子体发育。这些类似的生殖功能表明，可能存在共同的机制来调控胚珠和花药的发育。拟南芥的两个生长素响应因子ARF6和ARF8，调控未成熟花中雌蕊和雄蕊的发育。野生型花粉在arf6 arf8雌蕊中生长不良，这与ARF6和ARF8在花柱和传递组织中的表达相关。ARF6和ARF8转录本是微小RNA miR167的切割靶点，过表达miR167会模拟arf6 arf8的表型。ARF6或ARF8的miR167靶位点发生突变，导致这些基因在胚珠和花药中通常存在miR167的区域异位表达。结果，胚珠珠被生长停滞，花药异常生长且无法释放花粉。因此，miR167对于基因表达的正确模式形成以及胚珠和花药的育性至关重要。miR167的基本模式形成功能与动物中的情况形成对比，在动物中，微小RNA强化或维持转录建立的基因表达模式。
