Project description:Tobacco mature pollen has extremely desiccated cytoplasm, and is metabolically quiescent. Upon re-hydration it becomes metabolically active and that results in later emergence of rapidly growing pollen tube. These changes in cytoplasm hydration and metabolic activity are accompanied by protein phosphorylation. In this study, we subjected mature pollen, 5-min-activated pollen, and 30-min-activated pollen to TCA/acetone protein extraction, trypsin digestion and phosphopeptide enrichment by titanium dioxide. The enriched fraction was subjected to nLC-MS/MS. We identified 471 phosphopeptides that carried 432 phosphorylation sites, position of which was exactly matched by mass spectrometry. These 471 phosphopeptides were assigned to 301 phosphoproteins, since some proteins carried more phosphorylation sites. Of the 13 functional groups, the majority of proteins were put into these categories: transcription, protein synthesis, protein destination and storage, and signal transduction. Many proteins were of unknown function, reflecting the fact that male gametophyte contains many specific proteins that have not been fully functionally annotated. The quantitative data highlighted the dynamics of protein phosphorylation during pollen activation; the identified phosphopeptides were divided into seven groups based on the regulatory trends. The major group comprised mature pollen-specific phosphopeptides that were dephosphorylated during pollen activation. Several phosphopeptides representing the same phosphoprotein had different regulation, which pinpointed the complexity of protein phosphorylation and its clear functional context. Collectively, we showed the first phosphoproteomics data on activated pollen where the position of phosphorylation sites was clearly demonstrated and regulatory kinetics was resolved.
Project description:Pollen germination and subsequent pollen tube elongation are essential for successful land plant reproduction. These processes are achieved through well-documented activation of membrane trafficking and cell metabolism. Despite this, our knowledge of the dynamics of cellular phospholipids remains scarce. In this project, we analyzed the turnover of the glycerolipid composition during the establishment of cell polarity and elongation processes in tobacco pollen and described the proteo-lipid composition of pollen plasma membrane-enriched. To achieve this, we have combined several techniques, such as lipidomics, live-cell microscopy, and plasma membrane isolation coupled with mass spectrometry-based proteomic characterization.
Project description:As in animals, cell-cell communication plays pivotal role in male-female recognition during plant sexual reproduction. Prelaid peptides secreted from the female reproductive tissues guide pollen tubes towards ovules for fertilization. However, the elaborate mechanisms for this dialogue have remained elusive, particularly from the male perspective. We perform genome-wide quantitative liquid chromatography coupled tandem mass spectrometry of a pistil-stimulated pollen tube secretome and identify 801 pollen tube-secreted proteins. Interestingly, in silico analysis reveals that the pollen tube-secretome is dominated by unconventional-type secreted proteins representing 57% of the total secretome. In support, we show that unconventional-type protein, translationally controlled tumor protein, is secreted to the apoplast. Remarkably, we discover that this protein could be secreted by infiltrating through the initial phases of the conventional secretory pathway and could reach the apoplast via exosomes as demonstrated by co-localization with Oleisin1 exosome marker. We demonstrate that Arabidopsis thaliana translationally controlled tumor protein-knockdown plants have pollen tubes that poorly navigate to the target ovule, and the knocked down allele is poorly transmitted through the male. We show that regulators of the endoplasmic reticulum-trans-golgi network protein secretory pathway control secretion of pollen tube-secreted cysteine-rich proteins, including pollen tube attractants, and are essential for pollen tube growth and guidance, as well as ovule-targeting competence. This work, the first pollen tube secretome study, identifies novel genome-wide pollen tube-secreted proteins with potential function in pollen tube-ovule guidance for sexual reproduction. Functional analysis highlights a potential mechanism for pollen tube unconventional protein secretion and reveals likely regulators of pollen tube protein secretion. The association of pollen tube-secreted proteins with marker proteins shown to be secreted via exosomes in other species suggest secretion via exosomes as a possible mechanism for cell-cell communication between the pollen tube and female reproductive cells. For processed dataset with quantitative information, see Hafidh S, Potesil D, Fila J et al. Genome Bilogy 2016.
Project description:Pollen development in angiosperms is one of the most important processes controlling plant reproduction and therefore productivity. At the same time pollen development is highly sensitive to environmental fluctuations including temperature, drought and nutrition. Therefore pollen biology is a major focus in applied studies and breeding approaches for improving plant productivity in a globally changing climate. The most accessible developmental stages of pollen are the mature pollen and the pollen tubes and are, thus, most frequently analyzed. To reveal a complete quantitative proteome map we additionally addressed the very early stages analyzing 8 stages of tobacco pollen development from diploid microsporocytes, meioses, tetrads, microspores, polarized microspores, bipolar pollen and desiccated pollen to pollen tubes. A protocol for the isolation of the early stages was established. Proteins were extracted and analyzed by a new Gel-LC-MS fractionation protocol. In total, 3817 protein groups were identified. Quantitative analysis was performed based on peptide count. Exceedingly stage-specific differential protein regulation was observed during the conversion from the sporophytic to the gametophytic proteome. A map of highly specialized functionality for the different stages could be revealed from metabolic activity, pronounced differentiation of proteasomal and ribosomal protein complex composition up to protective mechanisms such as high levels of heat shock proteins in the very early stages of development.
Project description:The number of known proteins associated with plant lipid droplets (LDs) is small compared to other organelles. Many questions of LD biosynthesis and degradation remain open, also due to lack of candidate LD proteins whose characterization could help to elucidate their function in those processes. We performed a proteomic screen on LDs isolated from Nicotiana tabacum pollen tubes. Proteins that were highly enriched in the LD fraction compared to the total or cytosolic fraction where verified for LD localization via transient expression in tobacco pollen tubes.
Project description:Pollen development in angiosperms is one of the most important processes controlling plant reproduction and thus productivity. At the same time, pollen development is highly sensitive to environmental fluctuations, including temperature, drought, and nutrition. Therefore, pollen biology is a major focus in applied studies and breeding approaches for improving plant productivity in a globally changing climate. The most accessible developmental stages of pollen are the mature pollen and the pollen tubes, and these are thus most frequently analyzed. To reveal a complete quantitative proteome map, we additionally addressed the very early stages, analyzing eight stages of tobacco pollen development: diploid microsporocytes, meiosis, tetrads, microspores, polarized microspores, bipolar pollen, desiccated pollen, and pollen tubes. A protocol for the isolation of the early stages was established. Proteins were extracted and analyzed by means of a new gel LC-MS fractionation protocol. In total, 3817 protein groups were identified. Quantitative analysis was performed based on peptide count. Exceedingly stage-specific differential protein regulation was observed during the conversion from the sporophytic to the gametophytic proteome. A map of highly specialized functionality for the different stages could be revealed from the metabolic activity and pronounced differentiation of proteasomal and ribosomal protein complex composition up to protective mechanisms such as high levels of heat shock proteins in the very early stages of development.
Project description:To investigate the function of previously cloned novel cysteine-rich peptide EaF82 which biochemical properties are similar to the Rapid Alkalinization Factor (RALF), we overexpressed EaF82 gene in Arabidopsis and found defects only in the pollen development. To further determine the affected genes and biological pathways, we compared the transcriptome profilings of two independent Arabidopsis EaF82 overexpressing lines (TA and TB) with that of the vector control line (C). The RNAseq analysis results revealed decreased expressions of five endogenous clade IV AtRALFs and genes responsible for cell wall modifications and pollen maturation, supporting the observed pollen abortion.
Project description:We isolated tricellular pollen (TCP) and pollen mother cells (PMC) of rice using laser microdissection, and did microarray analysis with Agilent 44k rice array.
Project description:Small non-coding RNAs play important roles during the development of eukaryotic organisms. Both animal and plant miRNAs are essential for the spatio-temporal regulation of development but together with this role, plant miRNAs, also control transposable elements and stimulate the production of epigenetically-active small interfering RNAs. This last role is evident in the plant male gamete containing structure, the male gametophyte or pollen grain but how the dual role of plant miRNAs is integrated during its development is unknown. Here, we provide a detailed analysis of miRNA dynamics during pollen development and their genic and transposable element targets using small RNA and PARE high-throughput sequencing. Furthermore we uncover the miRNAs loaded in the two main AGOs in the mature pollen grain, AGO1 and AGO5. Our results indicate that the progression from microspore to mature pollen grain is characterized by a reprogramming from miRNAs focused on the control of development to miRNAs focused in transposable element control.