Biology subjects

Dresselhaus, T.

Publications and source records attributed to Dresselhaus, T..

9 recordsLinked to original sources

bioRxiv2026

The SWI/SNF subunit SWI3B functions with the m6A writer complex to establish embryo patterning in Arabidopsis

N6-methyladenosine (m6A) is the most abundant mRNA modification in eukaryotes and is essential for Arabidopsis embryogenesis. However, how m6A mRNA methylation is coordinated with other regulatory pathways during development including embryogenesis remains largely unknown. Here, we report the SWI/SNF chromatin-remodeling subunit SWI3B as a bona fide interactor of the m6A methyltransferase MTA. Like m6A writer mutants, SWI3B is required for early embryo development. We demonstrate that the interaction between MTA and SWI3B is required for MTA function during embryogenesis. MTA and SWI3B are both required to establish the correct expression pattern of WOX8 and proper auxin maxima during early embryogenesis. Transcriptome analysis of isolated embryos from mta, swi3b, and fip37 mutants identified a shared set of upregulated transcripts, including STM as well as several NAC and ERF transcription factors that are normally absent or expressed at very low levels during early embryogenesis. Embryo-specific overexpression of ANAC087 and ERF114 genes phenocopied early embryonic defects observed in mta and swi3b mutants, indicating that their ectopic expression contributes to the observed developmental phenotype. Moreover, SWI3B and MTA are both required for m6A deposition on specific developmental transcripts. Together, our findings uncover a mechanism by which chromatin remodeling and m6A-mediated RNA regulation cooperate to suppress the precocious stability of key developmental regulators, thereby contributing to the establishment of the transcriptional program required for early embryo patterning in Arabidopsis. HighlightsO_LIThe SWI/SNF subunit SWI3B is a functional interactor of the m6A methyltransferase MTA during Arabidopsis embryogenesis C_LIO_LISWI3B and MTA cooperate to establish embryo patterning, WOX8 expression, and auxin maxima C_LIO_LIMTA and SWI3B suppress precocious expression of STM, ANAC087 and ERF114 transcription factors that disrupt early embryo development C_LIO_LISWI3B links chromatin-associated regulation with m6A-mediated control of transcript stability C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=161 HEIGHT=200 SRC="FIGDIR/small/744595v1_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@1056f76org.highwire.dtl.DTLVardef@1d8b9d6org.highwire.dtl.DTLVardef@190918corg.highwire.dtl.DTLVardef@439ce1_HPS_FORMAT_FIGEXP M_FIG C_FIG

plant biology↗

bioRxiv2026

SWI3b restricts AGO5 expression to promote the initiation of megagametogenesis in Arabidopsis

Female germline development is fundamental to plant reproduction. During megasporogenesis, a somatic ovule cell differentiates into a megaspore mother cell (MMC) and undergoes meiosis to produce a single haploid megaspore while three spores degenerate. The surviving functional megaspore undergoes three rounds of mitosis during the process of megagametogenesis to produce the seven-celled female gametophyte or embryo sac. The mechanism by which the functional megaspore initiates gametogenesis remained unclear. Here, we show that the chromatin remodelling protein SWI3b is required for the initiation of megagametogenesis, but not for megasporogenesis. SWI3b activity either in the MMC or somatic ovule primordium cells alone is not sufficient for the initiation of megagametogenesis. We identified AGO5 as a direct target of SWI3b, which restricts AGO5 expression to the nucellus. We further show that SWI3b is required for maintaining low histone H3 lysine 9 acetylation level at the AGO5 locus, while elevated AGO5 abundance in the nucellus disrupts the initiation of megagametogenesis. In summary, our study reveals that SWI3b promotes the initiation of megagametogenesis through chromatin-mediated repression of AGO5, leading to its exclusion from the MMC and thereby linking histone acetylation and epigenetic mechanisms to the development of the female germ cells. HighlightsO_LIThe chromatin remodeling complex component SWI3b is required for the initiation of megagametogenesis and early embryo development. C_LIO_LIIn ovule primordia SWI3b restricts AGO5 expression to the nucellus C_LIO_LISWI3b acts via regulating histone acetylation around the AGO5 transcription start site. C_LIO_LIDevelopment of female germ cells are associated to histone acetylation C_LI

plant biology↗

bioRxiv2025

The secreted redox sensor roGFP2-Orp1 reveals oxidative dynamics in the plant apoplast

- Specific generation of reactive oxygen species (ROS) is important for signalling and defence in many organisms. In plants, different types of ROS serve useful biological functions in the extracellular space (apoplast), influencing polymer structures as well as signaling during immune responses. The current knowledge of apoplastic ROS dynamics is limited, as dynamic monitoring of extracellular redox processes in vivo remains difficult. - We employed evolutionary distant land plant model species from bryophytes and flowering plants to test whether the genetically encoded redox biosensor roGFP2-Orp1 can be used to assess extracellular redox dynamics. - Secreted roGFP2-Orp1 can inform about local diffusion barriers and protein cysteinyl oxidation rate in the apoplast, after pre-reduction. Observed re-oxidation rates were slow, within the range of hours. Compared to Physcomitrium patens, re-oxidation in Arabidopsis thaliana was faster and increased after triggering an immune response. Comparing roGFP2-Orp1 signals in tip-growing P. patens protonema and Nicotiana tabacum pollen tubes, we consistently find no intracellular redox gradient, but partially reduced extracellular sensor in pollen tubes. - Our data indicate differences in extracellular oxidative processes between species and within a species, depending on cell type and immune signalling.

plant biology↗

bioRxiv2024

Maize stigmas react differently to self-/cross-pollination and fungal invasion

During sexual reproduction in flowering plants, rapid tip-growing pollen tubes travel from the stigma inside the maternal tissues of the pistil towards ovules. In maize, the stigma is highly elongated forming thread-like strands known as silks. Only compatible pollen tubes are supported to penetrate and to grow successfully through the transmitting tract of the silk to reach the ovules. Like pollen, fungal spores germinate at the surface of silks and generate tube-like structures (hyphae) penetrating silk tissue. To elucidate commonalities and differences between silk responses to various invaders, we compared growth behavior of the various invaders as well as the silk transcriptome after self-pollination, cross-pollination and infection using two different fungi. We report that self-pollination triggers especially senescence genes, while incompatible pollination using Tripsacum dactyloides leads to downregulation of rehydration genes, microtubule and modulation of cell wall-related genes explaining slower pollen tube growth and their arrest. Invasion by the ascomycete Fusarium graminearum triggers numerous defense responses including the activation of monolignol biosynthesis and NAC as well as WRKY transcription factor genes, while responses to the basidiomycete Ustilago maydis are generally much weaker. Cell wall and phytoalexin biosynthesis pathways were selected as examples to demonstrate usability of the data sets provided. One sentence summaryData sets are provided and analyzed to elucidate how maize stigmas (silks) respond to different biotic invaders including own and alien pollen tubes as well as hyphae of two different fungi.

plant biology↗

bioRxiv2024

Fertilization-induced synergid cell death by RALF12-triggered ROS production and ethylene signaling

Fertilization-dependent elimination of the persistent synergid cell is essential to block supernumerary pollen tubes and thus to avoid polyspermy in flowering plants. Little is known about the molecular mechanisms ensuring timely induction and execution of synergid cell death. We analysed manually isolated maize synergid cells along their degeneration and show that they are gland cells expressing batteries of genes encoding small secreted proteins under control of the MYB98 transcription factor. This network is down-regulated after fertilization, while genes involved in reactive oxygen species (ROS) production, ethylene biosynthesis and response, senescence, and oxidative stress regulation are induced before synergid elimination and its ultimate fusion with the endosperm. We further show that fertilization-induced RALF12 peptide specifically triggers mitochondrial ROS and apoptosis, while ethylene promotes synergid degeneration. In conclusion, this study sheds light on developmental programmed cell death (dPCD) in plants and provides a unique resource to discover novel PCD regulators.

cell biology↗

bioRxiv2023

Heat stress at the bicellular stage inhibits sperm cell development and their transport into pollen tubes

For a successful double fertilization process in flowering plants (angiosperms), pollen tubes each deliver two non-motile sperm cells towards female gametes (egg and central cell, respectively). Heatwaves especially during the reproduction period are threatening male gametophyte (pollen) development, which results in severe yield losses. By using maize as a crop and grass model system, we found strong seed set reduction when moderate heat stress was applied for two days during the uni- and bicellular stages of pollen development. We show that heat stress accelerates pollen development and impairs pollen germination capabilities, when applied at the unicellular stage. Heat stress at the bicellular stage impairs sperm cell development and their transport into pollen tubes. To understand the course of the latter defects, we used marker lines and analyzed the transcriptomes of isolated sperm cells. While heat stress also affects the expression of genes involved in transcription, RNA processing and translation, especially genes in DNA replication and the cell cycle were mis-regulated. This includes centromeric histone CENH3 and -tubulin. Most mis-regulated genes are involved in transition from metaphase to anaphase during pollen mitosis II (PM II). Heat stress activates spindle assembly check point and meta-to anaphase transition genes in sperm cells. In summary, mis-regulation of the identified genes during heat stress at the bicellular stage explains sperm cell development and transport defects ultimately leading to sterility.

plant biology↗

bioRxiv2023

The RALF Signaling Pathway Regulates Cell Wall Integrity during Pollen Tube Growth in Maize

Autocrine signaling pathways regulated by RAPID ALKALINIZATION FACTORs (RALFs) control cell wall integrity during pollen tube germination and growth in Arabidopsis. To investigate the role of pollen-specific RALFs in another plant species, we combined gene expression data with phylogenetic and biochemical studies to identify candidate orthologs in maize. We show that Clade IB ZmRALF2/3 mutants, but not that of Clade III ZmRALF1/5 caused cell wall instability in the sub-apical region of the growing pollen tube. ZmRALF2/3 are mainly located to the cell wall and are partially able to complement the pollen germination defect of their Arabidopsis orthologs AtRALF4/19. Mutations in ZmRALF2/3 compromise pectin distribution pattern leading to altered cell wall thickness, hyperphosphorylation of ZmPEX cell wall proteins and pollen tube burst. Clade IB, but not Clade III ZmRALFs are capable to interact with pollen-specific CrRLK1L receptor kinases ZmFERL4/7/9 and GPI-anchored co-receptors ZmLLG1/2 at similar binding affinities. In contrast, binding affinity to ZmPEX2/4 cell wall proteins is about five times higher. Based on these data, we now propose a dosage-dependent model showing how Clade IB RALFs act as extracellular sensors to regulate cell wall integrity and thickness during pollen tube growth in plants. One sentence summaryPollen-specific RALFs interact at different binding affinities with receptor kinases, GPI-anchored proteins and cell wall proteins to regulate cell wall integrity during pollen tube growth in maize.

developmental biology↗

bioRxiv2020

Comparative transcriptomic analysis reveals conserved transcriptional programs underpinning organogenesis and reproduction in land plants

The evolution of plant organs, including leaves, stems, roots, and flowers, mediated the explosive radiation of land plants, which shaped the biosphere and allowed the establishment of terrestrial animal life. Furthermore, the fertilization products of angiosperms, seeds serve as the basis for most of our food. The evolution of organs and immobile gametes required the coordinated acquisition of novel gene functions, the co-option of existing genes, and the development of novel regulatory programs. However, our knowledge of these events is limited, as no large-scale analyses of genomic and transcriptomic data have been performed for land plants. To remedy this, we have generated gene expression atlases for various organs and gametes of 10 plant species comprising bryophytes, vascular plants, gymnosperms, and flowering plants. Comparative analysis of the atlases identified hundreds of organ- and gamete-specific gene families and revealed that most of the specific transcriptomes are significantly conserved. Interestingly, the appearance of organ-specific gene families does not coincide with the corresponding organs appearance, suggesting that co-option of existing genes is the main mechanism for evolving new organs. In contrast to female gametes, male gametes showed a high number and conservation of specific genes, suggesting that male reproduction is highly specialized. The expression atlas capturing pollen development revealed numerous transcription factors and kinases essential for pollen biogenesis and function. To provide easy access to the expression atlases and these comparative analyses, we provide an online database, www.evorepro.plant.tools, that allows the exploration of expression profiles, organ-specific genes, phylogenetic trees, co-expression networks, and others.

evolutionary biology↗

bioRxiv2019

Elucidating small RNA pathways in Arabidopsis thaliana egg cells

O_LISmall RNA pathway components and small RNA profiles of flowering plant egg cells are largely unexplored, mainly because they are not easily accessible but deeply buried inside the ovary.\nC_LIO_LIWe describe here the utilization of proliferating callus tissue that adopted transcriptome features of Arabidopsis egg cell as a tool to explore small RNA pathway components and small RNA profiles in egg cells. We furthermore complement our studies with mRNA-Seq data from isolated Arabidopsis egg cells and provide data validation by promoter-reporter studies and whole mount in situ hybridization.\nC_LIO_LISequencing of small RNA libraries demonstrate the predominance of TE-derived siRNAs in the egg cell-related callus. TE-features and expression profiles suggest post-transcriptional silencing of activated Gypsy-like LTR retrotransposons, whereas the majority of class II DNA transposons belonging to Copia, CACTA, hAT-like and Mutator superfamilies are subjected to transcriptional silencing.\nC_LIO_LISmall RNA-seq furthermore led to the identification of differentially expressed known and novel miRNAs whose expression in the egg cell was verified by small RNA whole mount in situ hybridization. Both the strong expression of miRNAs in the egg-cell-adjoining synergids and the secretion of miRNAs into the micropyle suggest hitherto undescribed roles for these accessory cells in intercellular communication with the egg cell and the arriving pollen tube.\nC_LIO_LIIn conclusion, our datasets provide valuable and comprehensive resources to study small RNA pathways and small-RNA-mediated epigenetic reprogramming during egg cell differentiation and the onset of plant embryogenesis.\nC_LI

plant biology↗