Publications (11)34.34 Total impact
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Article: Deep Sequencing Reveals Transcriptome Re-Programming of Taxus × media Cells to the Elicitation with Methyl Jasmonate.
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ABSTRACT: BACKGROUND: Plant cell culture represents an alternative source for producing high-value secondary metabolites including paclitaxel (Taxol®), which is mainly produced in Taxus and has been widely used in cancer chemotherapy. The phytohormone methyl jasmonate (MeJA) can significantly increase the production of paclitaxel, which is induced in plants as a secondary metabolite possibly in defense against herbivores and pathogens. In cell culture, MeJA also elicits the accumulation of paclitaxel; however, the mechanism is still largely unknown. METHODOLOGYPRINCIPAL FINDINGS: To obtain insight into the global regulation mechanism of MeJA in the steady state of paclitaxel production (7 days after MeJA addition), especially on paclitaxel biosynthesis, we sequenced the transcriptomes of MeJA-treated and untreated Taxus × media cells and obtained ∼ 32.5 M high quality reads, from which 40,348 unique sequences were obtained by de novo assembly. Expression level analysis indicated that a large number of genes were associated with transcriptional regulation, DNA and histone modification, and MeJA signaling network. All the 29 known genes involved in the biosynthesis of terpenoid backbone and paclitaxel were found with 18 genes showing increased transcript abundance following elicitation of MeJA. The significantly up-regulated changes of 9 genes in paclitaxel biosynthesis were validated by qRT-PCR assays. According to the expression changes and the previously proposed enzyme functions, multiple candidates for the unknown steps in paclitaxel biosynthesis were identified. We also found some genes putatively involved in the transport and degradation of paclitaxel. Potential target prediction of miRNAs indicated that miRNAs may play an important role in the gene expression regulation following the elicitation of MeJA. CONCLUSIONSSIGNIFICANCE: Our results shed new light on the global regulation mechanism by which MeJA regulates the physiology of Taxus cells and is helpful to understand how MeJA elicits other plant species besides Taxus.PLoS ONE 01/2013; 8(4):e62865. · 4.09 Impact Factor -
Article: miRDeepFinder: a miRNA analysis tool for deep sequencing of plant small RNAs.
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ABSTRACT: miRDeepFinder is a software package developed to identify and functionally analyze plant microRNAs (miRNAs) and their targets from small RNA datasets obtained from deep sequencing. The functions available in miRDeepFinder include pre-processing of raw data, identifying conserved miRNAs, mining and classifying novel miRNAs, miRNA expression profiling, predicting miRNA targets, and gene pathway and gene network analysis involving miRNAs. The fundamental design of miRDeepFinder is based on miRNA biogenesis, miRNA-mediated gene regulation and target recognition, such as perfect or near perfect hairpin structures, different read abundances of miRNA and miRNA*, and targeting patterns of plant miRNAs. To test the accuracy and robustness of miRDeepFinder, we analyzed a small RNA deep sequencing dataset of Arabidopsis thaliana published in the GEO database of NCBI. Our test retrieved 128 of 131 (97.7%) known miRNAs that have a more than 3 read count in Arabidopsis. Because many known miRNAs are not associated with miRNA*s in small RNA datasets, miRDeepFinder was also designed to recover miRNA candidates without the presence of miRNA*. To mine as many miRNAs as possible, miRDeepFinder allows users to compare mature miRNAs and their miRNA*s with other small RNA datasets from the same species. Cleaveland software package was also incorporated into miRDeepFinder for miRNA target identification using degradome sequencing analysis. Using this new computational tool, we identified 13 novel miRNA candidates with miRNA*s from Arabidopsis and validated 12 of them experimentally. Interestingly, of the 12 verified novel miRNAs, a miRNA named AC1 spans the exons of two genes (UTG71C4 and UGT71C3). Both the mature AC1 miRNA and its miRNA* were also found in four other small RNA datasets. We also developed a tool, "miRNA primer designer" to design primers for any type of miRNAs. miRDeepFinder provides a powerful tool for analyzing small RNA datasets from all species, with or without the availability of genome information. miRDeepFinder and miRNA primer designer are freely available at http://www.leonxie.com/DeepFinder.php and at http://www.leonxie.com/miRNAprimerDesigner.php , respectively. A program (called RefFinder: http://www.leonxie.com/referencegene.php ) was also developed for assessing the reliable reference genes for gene expression analysis, including miRNAs.Plant Molecular Biology 01/2012; · 4.15 Impact Factor -
Article: De novo sequencing and a comprehensive analysis of purple sweet potato (Impomoea batatas L.) transcriptome.
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ABSTRACT: High-throughput RNA sequencing was performed for comprehensively analyzing the transcriptome of the purple sweet potato. A total of 58,800 unigenes were obtained and ranged from 200 nt to 10,380 nt with an average length of 476 nt. The average expression of one unigene was 34 reads per kb per million reads (RPKM) with a maximum expression of 1,935 RPKM. At least 40,280 (68.5%) unigenes were identified to be protein-coding genes, in which 11,978 and 5,184 genes were homologous to Arabidopsis and rice proteins, respectively. Gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) analysis showed that 19,707 (33.5%) unigenes were classified to 1,807 terms of GO including molecular functions, biological processes, and cellular components and 9,970 (17.0%) unigenes were enriched to 11,119 KEGG pathways. We found that at least 3,553 genes may be involved in the biosynthesis pathways of starch, alkaloids, anthocyanin pigments, and vitamins. Additionally, 851 potential simple sequence repeats (SSRs) were identified in all unigenes. Transcriptome sequencing on tuberous roots of the sweet potato yielded substantial transcriptional sequences and potentially useful SSR markers which provide an important data source for sweet potato research. Comparison of two RNA-sequence datasets from the purple and the yellow sweet potato showed that UDP-glucose-flavonoid 3-O-glucosyltransferase was one of the key enzymes in the pathway of anthocyanin biosynthesis and that anthocyanin-3-glucoside might be one of the major components for anthocyanin pigments in the purple sweet potato. This study contributes to the molecular mechanisms of sweet potato development and metabolism and therefore that increases the potential utilization of the sweet potato in food nutrition and pharmacy.Planta 01/2012; 236(1):101-13. · 3.00 Impact Factor -
Article: Transcriptome-wide identification and stress properties of the 14-3-3 gene family in cotton (Gossypium hirsutum L.).
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ABSTRACT: 14-3-3s are a class of conserved proteins in eukaryotes involved in almost all cellular processes. Published studies have shown that this family plays a role in response to stress conditions. In this study, comparative genomics identified thirty-one 14-3-3 cDNAs encoding 25 unique proteins with transcripts that were sufficiently divergent in the coding regions to define different 14-3-3 members. Phylogenetic analysis indicated that the cotton 14-3-3 family was similar to the family in the plant model species Arabidopsis and rice. The multiple copies of 14-3-3 genes in cotton are suggested to be the result of a recent duplication event after the divergence of cotton from its progenitor species. 14-3-3s are differentially expressed in a range of cotton organs as well as under different environmental conditions. Salinity and drought stress significantly induced the altered expression of 14-3-3 genes, suggesting that 14-3-3s play a role in cotton response to environmental abiotic stress. The 14-3-3 gene CGF14-4 was more sensitive to both drought and salinity stress with a 10.2-fold change under 1% of PEG treatment, while other 14-3-3s responded only to either drought or salinity stress. These results implied that specific isoforms of 14-3-3s play different regulatory roles in stress response besides their role in development. 14-3-3s were more sensitive to abiotic stress in roots than in leaves, suggesting that the root is more sensitive to stress treatment than leaves. The differential expression pattern of 14-3-3s also suggests the occurrence of functional divergence among specific isoforms.Functional & Integrative Genomics 07/2011; 11(4):627-36. · 3.83 Impact Factor -
Article: Genome-wide functional analysis of the cotton transcriptome by creating an integrated EST database.
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ABSTRACT: A total of 28,432 unique contigs (25,371 in consensus contigs and 3,061 as singletons) were assembled from all 268,786 cotton ESTs currently available. Several in silico approaches [comparative genomics, Blast, Gene Ontology (GO) analysis, and pathway enrichment by Kyoto Encyclopedia of Genes and Genomes (KEGG)] were employed to investigate global functions of the cotton transcriptome. Cotton EST contigs were clustered into 5,461 groups with a maximum cluster size of 196 members. A total of 27,956 indel mutants and 149,616 single nucleotide polymorphisms (SNPs) were identified from consensus contigs. Interestingly, many contigs with significantly high frequencies of indels or SNPs encode transcription factors and protein kinases. In a comparison with six model plant species, cotton ESTs show the highest overall similarity to grape. A total of 87 cotton miRNAs were identified; 59 of these have not been reported previously from experimental or bioinformatics investigations. We also predicted 3,260 genes as miRNAs targets, which are associated with multiple biological functions, including stress response, metabolism, hormone signal transduction and fiber development. We identified 151 and 4,214 EST-simple sequence repeats (SSRs) from contigs and raw ESTs respectively. To make these data widely available, and to facilitate access to EST-related genetic information, we integrated our results into a comprehensive, fully downloadable web-based cotton EST database (www.leonxie.com).PLoS ONE 01/2011; 6(11):e26980. · 4.09 Impact Factor -
Article: Identification and characterization of microRNAs and their target genes in tobacco (Nicotiana tabacum).
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ABSTRACT: microRNAs (miRNAs) are a recently discovered class of small (~21 nt) endogenous gene regulators that have been shown to play an important role in plant growth and development by aiding in organ maturation, hormone signaling, tissue differentiation, and plant tolerance to environmental stress. Since a list of miRNAs has never been generated for tobacco, we employed genome survey sequence analysis to computationally identify 259 potentially conserved tobacco miRNAs, belonging to 65 families, and validated 11 of these miRNAs using qRT-PCR. The 65 miRNA families were dramatically different in size. miRNA precursor (pre-miRNA) sequence analysis showed that tobacco pre-miRNAs greatly varied from 45 to 635 nt in length with an average of 141 ± 108 nt. We were also able to determine the presence of antisense miRNAs as well as miRNA clusters in tobacco. Using previously established protocols, a total of 1,225 potential target genes were predicted for the newly identified tobacco miRNAs. These target genes include transcription factors, DNA replication proteins, metabolic enzymes, as well as other gene targets necessary for proper plant maturation. The results of this study show that conserved miRNAs exist in tobacco and suggest that these miRNAs may play an important role in tobacco growth and development.Planta 11/2010; 232(6):1289-308. · 3.00 Impact Factor -
Article: Target-align: a tool for plant microRNA target identification.
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ABSTRACT: MicroRNAs (miRNAs) are important regulatory molecules. A critical step in elucidating miRNA function is identifying potential miRNA targets. However, few reliable tools have been developed for identifying miRNA targets in plants. Here, we developed a Smith-Waterman-like alignment tool in order to accurately predict miRNA targets. Dynamic programming was used to build a score matrix based on the complementarity of nucleotides in order to trace the optimal local alignments. Important parameters, such as maximum mismatches and maximum consecutive mismatches between miRNAs and their targets, were also used for filtering the optimal local alignments. Almost all of the parameters in this alignment tool can be adjusted by users. Compared to other target prediction tools, Target-align exhibits strong sensitivity and accuracy for identifying miRNA targets. More importantly, Target-align can identify multi-target sites as well potential for non-cleaved targets sites by change the default settings. Windows, web and command-line versions were developed to better serve different users. http://www.leonxie.com/targetAlign.php. zhangb@ecu.edu Supplementary data are available at Bioinformatics online.Bioinformatics 10/2010; 26(23):3002-3. · 5.47 Impact Factor -
Article: Identification, characterization and expression analysis of MicroRNAs and their targets in the potato (Solanum tuberosum).
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ABSTRACT: MicroRNAs (miRNAs) are recognized as a class of important post-transcriptional expression regulators that act on their target genes by degradation of target mRNAs or by inhibition of target protein translation. Compared with the current numbers of identified miRNAs for other species in the plant kingdom, a large number of potential miRNAs remains to be identified in potato. In this study, using a newly modified comparative genome strategy, a total of 202 potential potato miRNAs were identified, which belong to 78 families. miR162, miR167, and miR396 are highly expressed in all tested organs. miR372 is highly expressed in flowers. A total of 1094 miRNA targets were predicted and some of them encode transcription factors as well as genes that function in stress response, signal transduction, and a variety of other metabolic processes. Gene ontology (GO) analysis implicates that these targets are involved in 545 biological processes. Of those processes, 28 are related to potato defense mechanisms against bacteria, viruses, and fungi, the metabolism of molecules such as carbon, sucrose, starch, and lipid, and the development of primary and lateral roots. Pathway enrichment analysis, based on the Kyoto Encyclopedia of Genes and Genomes (KEGG), demonstrates that the identified miRNAs participated in 98 metabolism networks, some of which include sucrose metabolism, fatty acid metabolism, amino acid metabolism, carbon fixation, and the biosynthesis of plant hormones.Gene 10/2010; 473(1):8-22. · 2.34 Impact Factor -
Article: In silico identification of conserved microRNAs and their target transcripts from expressed sequence tags of three earthworm species.
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ABSTRACT: MicroRNAs are a recently identified class of small regulatory RNAs that target more than 30% protein-coding genes. Elevating evidence shows that miRNAs play a critical role in many biological processes, including developmental timing, tissue differentiation, and response to chemical exposure. In this study, we applied a computational approach to analyze expressed sequence tags, and identified 32 miRNAs belonging to 22 miRNA families, in three earthworm species Eisenia fetida, Eisenia andrei, and Lumbricus rubellus. These newly identified earthworm miRNAs possess a difference of 2-4 nucleotides from their homologous counterparts in Caenorhabditis elegans. They also share similar features with other known animal miRNAs, for instance, the nucleotide U being dominant in both mature and pre-miRNA sequences, particularly in the first position of mature miRNA sequences at the 5' end. The newly identified earthworm miRNAs putatively regulate mRNA genes that are involved in many important biological processes and pathways related to development, growth, locomotion, and reproduction as well as response to stresses, particularly oxidative stress. Future efforts will focus on experimental validation of their presence and target mRNA genes to further elucidate their biological functions in earthworms.Computational biology and chemistry 10/2010; 34(5-6):313-9. · 1.37 Impact Factor -
Article: Identification and characterization of microRNAs and their targets in the bioenergy plant switchgrass (Panicum virgatum).
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ABSTRACT: MicroRNAs (miRNAs) are a class of non-coding small endogenous RNAs with lengths of approximately 22 nucleotides (nt) that have been shown to regulate gene expression at the post-transcriptional levels by targeting mRNAs for degradation or by inhibiting protein translation. Although thousands of miRNAs have been identified in many species, miRNAs have not yet been identified in switchgrass (Panicum virgatum), one of the most important bioenergy crops in the United States and around the world. In this study, we identified 121 potential switchgrass miRNAs, belonging to 44 families, using a well-defined comparative genome-based computational approach. We also identified miRNA clusters and antisense miRNAs in switchgrass expressed sequences tags. These identified miRNAs potentially target 839 protein-coding genes, which can act as transcription factors, and take part in multiple biological and metabolic processes including sucrose and fat metabolism, signal transduction, stress response, and plant development. Gene ontology (GO) analysis, based on these targets, showed that 527 biological processes were involved. Twenty-five of these processes were demonstrated to participate in the metabolism of carbon, glucose, starch, fatty acid, and lignin and in xylem formation. According to pathway enrichment analysis based on Kyoto Encyclopedia of Genes and Genomes (KEGG), 118 metabolism networks were found. These networks are involved in sucrose metabolism, fat metabolism, carbon fixation, hormone regulation, oxidative stress response, and the processing of other secondary metabolites.Planta 07/2010; 232(2):417-34. · 3.00 Impact Factor -
Conference Proceeding: In silico identification of microRNAs from expressed sequence tags of three earthworm species.
Proceedings of the First ACM International Conference on Bioinformatics and Computational Biology, BCB 2010, Niagara Falls, NY, USA, August 2-4, 2010; 01/2010
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Institutions
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2010–2012
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East Carolina University
- Department of Biology
Greenville, NC, USA
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