Project description:When pollen lands on a receptive stigma, it germinates and extends a tube inside the transmitting tissue of the pistil to deliver the sperm cells for double fertilization. The growth of the pollen tube triggers significant alterations in its gene expression. The extent to which these changes occur in the vegetative cell or extend to the sperm cells transported by the tube is unclear, but important to determine since sperm cells are believed to acquire a competency for fertilization during pollen-pistil interactions. To address these questions, we compared the transcriptomes of Arabidopsis thaliana sperm cells and vegetative nuclei isolated from mature pollen grains with those isolated from in vitro grown pollen tubes. Importantly, we also compared with transcriptomes of sperm cells obtained from pollen tubes grown under semi in vivo conditions where tubes passed through a pistil section. Our data shows that extensive transcriptomic changes occur in sperm cells during pollen tube growth, some of which are elicited only as sperms are carried through the pistil. Their analysis reveals a host of previously unidentified transcripts that may facilitate sperm maturation and gamete fusion. The vegetative cell undergoes even more extensive transcriptomic reprogramming during pollen tube growth, mainly through the upregulation of genes associated with pollen tube growth and vesicle-mediated transport. Interestingly, ATAC-seq data shows that the promoters of genes up-regulated in sperm during pollen tube growth are already accessible in sperm chromatin of mature pollen grains, suggesting pre-configured promoter accessibility. This study's expression data can be further explored here: https://bar.utoronto.ca/eFP-Seq_Browser/.
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 tube growth is important process for successful double fertilization, which is critical for grain yield in crop plants. Despite much progress in identification of rapid alkalization factors (RALFs) which serve as ligand for signaling transduction during fertilization in Arabidopsis, there is no functional study of RALF in mono-cotyledon plant. - We functionally characterized two pollen specific RALF in rice (Oryza sativa) using multiple CRISPR/Cas9 induced loss-of-function mutants, peptide treatment, expression analyses, tag reporter lines. - OsRALF17 is specifically expressed in pollen and pollen tube as the strongest level among 41 RALF members in rice. Exogenously applied OsRALF17 inhibits pollen tube germination and elongation at high concentration, but enhances tube elongation at low concentration, indicating the regulation of growth balance. Double mutant of OsRALF17 with OsRALF19 exhibit almost male sterile, with defect on pollen germination and tube elongation. - Our study revealed that functionally-redundant OsRALF17 and 19 peptides binds to the OsMTD2, CrRLK1L family member, and transmits ROS signal for pollen tube germination and integrity maintenance in rice. We provide new insights into the role of RALF and expanding our understanding of the biological role of RALF in regulating rice fertilization.
Project description:Transcriptional profiling in open flowers of Arabidopsis wild type control plants and sdg4 mutant (SALK T-DNA line_128444). The sdg4 mutant is a Arabidopsis T-DNA mutant in which T-DNA is inserted in a SET domain protein, SDG4 (At4g30860). Expression profiling studies indicate that SDG4 might function in modulating the expression of the genes that function in the growth of pollen tubes. Keywords: epigenetic modification
Project description:Sperm cells of seed plants have lost their motility and are transported by the vegetative pollen tube cell for fertilization. The extent to which sperm cells regulate their own transportation is a long-standing debate. By using the novel Arabidopsis double mutant drop1 drop2, we demonstrate here that sperm cells are only passive cargo and that the vegetative tube cell as a vehicle controls the entire journey.
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.