Population genomics of Marchantia polymorpha subsp. ruderalis reveals evidence of climate adaptation.

Sexual reproduction results in the development of haploid and diploid cell states during the life cycle. In bryophytes, the dominant multicellular haploid phase produces motile sperm that swim through water to the egg to effect fertilization from which a relatively small diploid phase develops. In angiosperms, the reduced multicellular haploid phase produces non-motile sperm that is delivered to the egg through a pollen tube to effect fertilization from which the dominant diploid phase develops.

Plant reproduction: Ancient origins of male germline differentiation.

Despite the wide diversity in male sexual development across land plants, new work reveals the conservation of a heterodimer of transcription factors as master regulators of the male germline.

The ancestral chromatin landscape of land plants.

Recent studies have shown that correlations between chromatin modifications and transcription vary among eukaryotes. This is the case for marked differences between the chromatin of the moss Physcomitrium patens and the liverwort Marchantia polymorpha. Mosses and liverworts diverged from hornworts, altogether forming the lineage of bryophytes that shared a common ancestor with land plants.

The Polycomb repressive complex 2 deposits H3K27me3 and represses transposable elements in a broad range of eukaryotes.

The mobility of transposable elements (TEs) contributes to evolution of genomes. Their uncontrolled activity causes genomic instability; therefore, expression of TEs is silenced by host genomes. TEs are marked with DNA and H3K9 methylation, which are associated with silencing in flowering plants, animals, and fungi.

Three-Dimensional Morphological Analysis Revealed the Cell Patterning Bases for the Sexual Dimorphism Development in the Liverwort Marchantia polymorpha.

In land plants, sexual dimorphism can develop in both diploid sporophytes and haploid gametophytes. While developmental processes of sexual dimorphism have been extensively studied in the sporophytic reproductive organs of model flowering plants such as stamens and carpels of Arabidopsis thaliana, those occurring in gametophyte generation are less well characterized due to the lack of amenable model systems. In this study, we performed three-dimensional morphological analyses of gametophytic sexual branch differentiation in the liverwort Marchantia polymorpha, using high-depth confocal imaging and a computational cell segmentation technique.

Polycomb-mediated repression of paternal chromosomes maintains haploid dosage in diploid embryos of .

Complex mechanisms regulate gene dosage throughout eukaryotic life cycles. Mechanisms controlling gene dosage have been extensively studied in animals, however it is unknown how generalizable these mechanisms are to diverse eukaryotes. Here, we use the haploid plant to assess gene dosage control in its short-lived diploid embryo.

Deep evolutionary origin of gamete-directed zygote activation by KNOX/BELL transcription factors in green plants.

KNOX and BELL transcription factors regulate distinct steps of diploid development in plants. In the green alga KNOX and BELL proteins are inherited by gametes of the opposite mating types and heterodimerize in zygotes to activate diploid development. By contrast, in land plants such as and , KNOX and BELL proteins function in meristem maintenance and organogenesis during the later stages of diploid development.

Building new insights in plant gametogenesis from an evolutionary perspective.

Extant bryophytes are thought to preserve characteristics of ancestral land plants, with a life cycle dominated by the haploid gametophyte. The gametophyte produces gametes in specialized organs that differentiate after an extensive phase of vegetative development. During land plant evolution, these organs became extremely reduced.

A -acting bidirectional transcription switch controls sexual dimorphism in the liverwort.

Plant life cycles alternate between haploid gametophytes and diploid sporophytes. While regulatory factors determining male and female sexual morphologies have been identified for sporophytic reproductive organs, such as stamens and pistils of angiosperms, those regulating sex-specific traits in the haploid gametophytes that produce male and female gametes and hence are central to plant sexual reproduction are poorly understood. Here, we identified a MYB-type transcription factor, MpFGMYB, as a key regulator of female sexual differentiation in the haploid-dominant dioicous liverwort, MpFGMYB is specifically expressed in females and its loss resulted in female-to-male sex conversion.

Plant-inspired pipettes.

The female sex organ of the liverwort () has a characteristic parasol-like form highly suitable for collecting water droplets containing sperm for fertilization. Motivated by this observation and using three-dimensional printing techniques, we develop a parasol-like rigid object that can grab, transport and release water droplets of a maximum size of about 1 cm. By combining experiments and scaling theory, we quantify the object's fundamental wetting and fluid dynamical properties.

Compensation: a key to clarifying the organ-level regulation of lateral organ size in plants.

Leaves are ideal model systems to study the organ size regulation of multicellular plants. Leaf cell number and cell size are determinant factors of leaf size which is controlled through cell proliferation and post-mitotic cell expansion, respectively. To achieve a proper leaf size, cell proliferation and post-mitotic cell expansion should be co-ordinated during leaf morphogenesis.

Small RNAs as positional signal for pattern formation.

Pattern formation in plant relies on intimate cell-cell communication exchanging positional information. While ligand-receptor interaction is commonly used by plants and animals as a means to transmit positional information, plant cells can directly exchange regulatory molecules such as transcription factors through a cytoplasmic continuum called the plasmodesmata. Recently endogenous small RNAs (sRNAs) of various biogenetic origins have been shown to function non-cell-autonomously.