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Abundant expression of maternal siRNAs is a conserved feature of seed development.
Proceedings of the National Academy of Sciences of the United States of America ( IF 11.1 ) Pub Date : 2020-06-30 , DOI: 10.1073/pnas.2001332117
Jeffrey W Grover 1 , Diane Burgess 2 , Timmy Kendall 3 , Abdul Baten 4, 5 , Suresh Pokhrel 6, 7 , Graham J King 4 , Blake C Meyers 6, 7 , Michael Freeling 8 , Rebecca A Mosher 9, 10
Affiliation  

Small RNAs are abundant in plant reproductive tissues, especially 24-nucleotide (nt) small interfering RNAs (siRNAs). Most 24-nt siRNAs are dependent on RNA Pol IV and RNA-DEPENDENT RNA POLYMERASE 2 (RDR2) and establish DNA methylation at thousands of genomic loci in a process called RNA-directed DNA methylation (RdDM). In Brassica rapa, RdDM is required in the maternal sporophyte for successful seed development. Here, we demonstrate that a small number of siRNA loci account for over 90% of siRNA expression during B. rapa seed development. These loci exhibit unique characteristics with regard to their copy number and association with genomic features, but they resemble canonical 24-nt siRNA loci in their dependence on RNA Pol IV/RDR2 and role in RdDM. These loci are expressed in ovules before fertilization and in the seed coat, embryo, and endosperm following fertilization. We observed a similar pattern of 24-nt siRNA expression in diverse angiosperms despite rapid sequence evolution at siren loci. In the endosperm, siren siRNAs show a marked maternal bias, and siren expression in maternal sporophytic tissues is required for siren siRNA accumulation. Together, these results demonstrate that seed development occurs under the influence of abundant maternal siRNAs that might be transported to, and function in, filial tissues.



中文翻译:

母体siRNA的大量表达是种子发育的保守特征。

小RNA在植物生殖组织中含量很高,尤其是24核苷酸(nt)小干扰RNA(siRNA)。大多数24-nt siRNA依赖于RNA Pol IV和依赖于RNA的RNA聚合酶2(RDR2),并在称为RNA定向DNA甲基化(RdDM)的过程中在数千个基因组位点建立DNA甲基化。在甘蓝型油菜中,成功的种子发育需要母体孢子体中的RdDM。在这里,我们证明了少量的siRNA基因座在B. rapa期间占siRNA表达的90%以上种子发育。这些基因座在拷贝数和与基因组特征的关联方面表现出独特的特征,但在对RNA Pol IV / RDR2的依赖性以及在RdDM中的作用方面,它们类似于规范的24 nt siRNA基因座。这些基因座在受精前在胚珠中表达,在受精后在种皮,胚和胚乳中表达。尽管在警笛位点快速序列进化,我们观察到在各种被子植物中24-nt siRNA表达的相似模式。在胚乳中,警报器siRNA显示出明显的母体偏倚,并且警报器siRNA积累需要母体孢子体组织中的警报器表达。在一起,这些结果表明,在丰富的母体siRNA的影响下发生了种子发育,这些siRNA可能被运送到孝子组织并在孝子组织中起作用。

更新日期:2020-06-30
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