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Dynamic parent-of-origin effects on small interfering RNA expression in the developing maize endospermXin, Mingming; Yang, Ruolin; Yao, Yingyin; Ma, Chuang; Peng, Huiru; Sun, Qixin; Wang, Xiangfeng; Ni, Zhongfu; State Key Laboratory for Agrobiotechnology, Key Laboratory of Crop Heterosis Utilization (MOE), Beijing Key Laboratory of Crop Genetic Improvement, China Agricultural University, NO.2 Yuanmingyuan Xi Road, Haidian District, Beijing 100193, China; School of Plant Sciences, University of Arizona, 1145 E. South Campus Drive, Tucson 85721-0036, AZ, USA (BioMed Central, 2014)Background:In angiosperms, the endosperm plays a crucial placenta-like role in that not only is it necessary for nurturing the embryo, but also regulating embryogenesis through complicated genetic and epigenetic interactions with other seed compartments and is the primary tissue in which genomic imprinting occurs.Results:We observed a gradual increase of paternal siRNA expression in the early stages of kernels and an expected 2:1 maternal to paternal ratio in 7-DAP endosperm via sequencing of small interfering RNA (siRNA) transcriptomes in developing kernels (0, 3 and 5 days after pollination (DAP)) and endosperms (7, 10 and 15 DAP) from the maize B73 and Mo17 reciprocal crosses. Additionally, 460 imprinted siRNA loci were identified in the endosperm, with the majority (456/460, 99.1%) being maternally expressed at 10 DAP. Moreover, 13 out of 29 imprinted genes harbored imprinted siRNA loci within their 2-kb flanking regions, a significant higher frequency than expected based on simulation analysis. Additionally, gene ontology terms of "response to auxin stimulus", "response to brassinosteroid stimulus" and "regulation of gene expression" were enriched with genes harboring 10-DAP specific siRNAs, whereas those of "nutrient reservoir activity", "protein localization to vacuole" and "secondary metabolite biosynthetic process" were enriched with genes harboring 15-DAP specific siRNAs.Conclusions:A subset of siRNAs subjected to imprinted expression pattern in maize developing endosperm, and they are likely correlated with certain imprinted gene expression. Additionally, siRNAs might influence nutrient uptake and allocation processes during maize endosperm development.
A novel two-layer SVM model in miRNA Drosha processing site detectionHu, Xingchi; Ma, Chuang; Zhou, Yanhong; Hubei Bioinformatics and Molecular Imaging Key Laboratory, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, 430074, China; School of Plant Sciences, University of Arizona, Tucson, AZ, USA (BioMed Central, 2013)BACKGROUND:MicroRNAs (miRNAs) are a large class of non-coding RNAs with important functions wide spread in animals, plants and viruses. Studies showed that an RNase III family member called Drosha recognizes most miRNAs, initiates their processing and determines the mature miRNAs. The Drosha processing sites identification will shed some light on both miRNA identification and understanding the mechanism of Drosha processing.METHODS:We developed a computational method for Drosha processing site predicting, named as DroshaPSP, which employs a two-layer mathematical model to integrate structure feature in the first layer and sequence features in the second layer. The performance of DroshaPSP was estimated by 5-fold cross-validation and measured by ACC (accuracy), Sn (sensitivity), Sp (specificity), P (precision) and MCC (Matthews correlation coefficient).RESULTS:The results of testing DroshaPSP on the miRNA data of Drosophila melanogaster indicated that the Sn, Sp, and MCC thereof reach to 0.86, 0.99 and 0.86 respectively.CONCLUSIONS:We found the Shannon entropy, a chemical kinetics feature, is a significant feature in telling the true sites among the nearby sites and improving the performance.