Project description:Pollen grains of Arabidopsis thaliana contain two haploid sperm cells enclosed in a haploid vegetative cell. Upon germination, the vegetative cell extrudes a pollen tube that carries the sperm to an ovule for fertilization. Knowing the identity, relative abundance, and splicing patterns of pollen transcripts will improve understanding of pollen and allow investigation of tissue-specific splicing in plants. Most Arabidopsis pollen transcriptome studies have used the ATH1 microarray, which does not assay splice variants and lacks specific probe sets for many genes. To investigate the pollen transcriptome, we performed high-throughput sequencing (RNA-Seq) of Arabidopsis pollen and seedlings for comparison. Gene expression was more diverse in seedling, and genes involved in cell wall biogenesis were highly expressed in pollen. RNA-Seq detected at least 4,172 protein coding genes expressed in pollen, including 289 assayed only by non-specific probe sets. Additional exons and previously unannotated 5’ and 3’ UTRs for pollen-expressed genes were revealed. We detected regions in the genome not previously annotated as expressed; 14 were tested and 12 confirmed by PCR. Gapped read alignments revealed 1,908 high-confidence new splicing events supported by 10 or more spliced read alignments. Alternative splicing patterns in pollen and seedling were highly correlated. For most alternatively spliced genes, the ratio of variants in pollen and seedling was similar, except for some encoding proteins involved in RNA splicing. This study highlights the robustness of splicing patterns in plants and the importance of on-going annotation and visualization of RNA-Seq data using interactive tools such as Integrated Genome Browser.
Project description:Pollen germination, along with pollen tube growth, is an essential process for the reproduction of flowering plants. The germinating pollen with tip-growth characteristics provides an ideal model system for the study of cell growth and morphogenesis. As an essential step towards a detailed understanding of this important process, the objective of this study was to comprehensively analyze the transcriptome changes during pollen germination and pollen tube growth. Using Affymetrix Arabidopsis ATH1 Genome Arrays, this study is the first to show the changes in the transcriptome from desiccated mature pollen grains to hydrated pollen grains and then to pollen tubes of Arabidopsis thaliana. The number of expressed genes, either for total expressed genes or for specifically expressed genes, increased significantly from desiccated mature pollen to hydrated pollen and again to growing pollen tubes, which is consistent with the finding that pollen germination and tube growth was significantly inhibited in vitro by a transcriptional inhibitor. The results of GO analyses showed that expression of genes related to cell rescue, transcription, signal transduction and cellular transport were significantly changed, especially for up-regulation, during pollen germination and tube growth, respectively. In particular, genes of the CaM/CML, CHX and Hsp families showed the most significant changes during pollen germination and tube growth. These results demonstrate that the overall transcription of genes, both in the number of expressed genes and in the levels of transcription, was increased. Furthermore, the appearance of many novel transcripts during pollen germination as well as tube growth indicates that these newly expressed genes may function in this complex process.
Project description:Purpose: Alternative splicing is fundamental for post-transcriptional regulation and proteome diversity. The goals of this study are to compare transcriptome and splicing profiling (RNA-seq) between wild type and prp8a prp8b mutant ovules of the spliceosome subunit and define the molecular signature of prp8a prp8b pollen tube attraction phenotype. Methods: mRNA profiles from mature ovules of 6-weeks-old wild-type (WT) and pre-mRNA processing factor 8 (PRP8Aa prp8bb) Arabidopsis plants were generated by deep sequencing, in triplicates, using Illumina HiSeq4000 100bp paired-end reads. The sequence reads that passed quality filters were were mapped to TAIR10 whole genome and analyzed for differential expression, differential exone usage and intron retention as indicated in DATA PROCESSING PIPELINE section. Results: Using an optimized data analysis workflow, about 15 million sequence read pairs per sample were mapped to the Arabidopsis genome (TAIR10). Approximately 2.9% of the transcripts showed differential expression between the WT and PRP8Aa prp8bb ovules, with a fold change ≥1.5 and p value <0.05. Analysis for differential gene expression, exon usage and intron retention with DESeq2 v1.22.1 and DEXseq v1.28.0 or IRFinder v1.2.3 respectively, uncovered several as yet uncharacterized genes that may contribute to pollen tube attraction and female gametophyte cell fate specification. Conclusions: Our work has uncovered a molecular signature through which PRP8A/PRP8B subunits act redundantly to define male-female signaling competence for successful pollen tube attraction in Arabidopsis. Application of DESeq2 algorithms to our ovule RNA-seq data identified downregulation of over 50 different CRP genes with yet unknown function from the synergid and the central cells including all LURE pollen tube attractants. Whereas use of DEXseq workflow, revealed mis-splicing of key genes involved embryo sac specificiation and genes of the secretory pathway. We concluded that 100bp paired-end RNAseq was a sufficient compromise for detection of differential gene expression and splice isoforms, however, our experiment would have benefited with more number of replicates.
Project description:Pollen germination, along with pollen tube growth, is an essential process for the reproduction of flowering plants. The germinating pollen with tip-growth characteristics provides an ideal model system for the study of cell growth and morphogenesis. As an essential step towards a detailed understanding of this important process, the objective of this study was to comprehensively analyze the transcriptome changes during pollen germination and pollen tube growth. Using Affymetrix Arabidopsis ATH1 Genome Arrays, this study is the first to show the changes in the transcriptome from desiccated mature pollen grains to hydrated pollen grains and then to pollen tubes of Arabidopsis thaliana. The number of expressed genes, either for total expressed genes or for specifically expressed genes, increased significantly from desiccated mature pollen to hydrated pollen and again to growing pollen tubes, which is consistent with the finding that pollen germination and tube growth was significantly inhibited in vitro by a transcriptional inhibitor. The results of GO analyses showed that expression of genes related to cell rescue, transcription, signal transduction and cellular transport were significantly changed, especially for up-regulation, during pollen germination and tube growth, respectively. In particular, genes of the CaM/CML, CHX and Hsp families showed the most significant changes during pollen germination and tube growth. These results demonstrate that the overall transcription of genes, both in the number of expressed genes and in the levels of transcription, was increased. Furthermore, the appearance of many novel transcripts during pollen germination as well as tube growth indicates that these newly expressed genes may function in this complex process. SUBMITTER_CITATION: Yi Wang, Wen-Zheng Zhang, Lian-Fen Song, Jun-Jie Zou, Zhen Su, and Wei-Hua Wu. Transcriptome analyses show changes in gene expression to accompany pollen germination and tube growth in Arabidopsis. Plant Physiol. September 5, 2008; 10.1104/pp.108.126375 Experiment Overall Design: Three samples are analyzed in this experiment. They are desiccated mature pollen grains (MP), hydrated pollen grains (HP) and growing pollen tubes (PT) of Arabidopsis thaliana, respectively. Each sample has two biological replicates, so that there are 6 data sets of ATH1 array in this experiment.
Project description:Upon germination, pollen forms a tube that elongates dramatically through female tissues in order to reach and fertilize ovules. While essential for the life cycle of higher plants, the genetic basis underlying most of the process is not well understood. We used Affymetrix Arabidopsis ATH1 Genome Arrays covering more than 80% of the Arabidopsis genome to compare transcriptomes of cell-sorted, hydrated pollen grains with those of flowers, leaves, seedlings and siliques (all samples with duplicates). This comparison revealed that pollen expresses a reduced set of genes with increased proportions of enriched and selectively-expressed transcripts. Relative gene ontology (GO) category representations in pollen and vegetative tissues revealed a functional skew of the pollen transcriptome towards signaling, vesicle transport and cytoskeleton, suggestive of a commitment towards germination and tube growth. Relative gene ontology (GO) category representations in pollen and vegetative tissues reveal a functional skew of the pollen transcriptome towards signaling, vesicle transport and cytoskeleton, suggestive of a commitment towards germination and tube growth. Relative gene ontology (GO) category representations in pollen and vegetative tissues reveal a functional skew of the pollen transcriptome towards signaling, vesicle transport and cytoskeleton, suggestive of a commitment towards germination and tube growth. Gene family and pathway analysis allowed formulation of novel hypotheses for the role of non-classical MADS-box genes, small RNA pathways and cell cycle components in pollen.
Project description:In this study, we investigated the differential metabolic pathway enrichment among mature, hydrated, and germinated pollen using untargeted metabolomics analysis. Integration of publicly available transcriptome with presented metabolome data revealed starch and sucrose metabolism was significantly increased during pollen hydration and germination. The alterations in central metabolism focusing on sugar, fatty acids, and lipids were analyzed in detail. Several metabolites, including palmitic acid, oleic acid, linolenic acid, quercetin, luteolin/kaempferol, and γ-aminobutyric acid (GABA), were elevated in the hydrated pollen, suggesting a potential role in activating pollen tube emergence. The metabolite levels of mature, hydrated, and germinated pollen, presented in this work provide insights on the molecular basis of pollen germination.