Rapid Elimination of the Persistent Synergid through a Cell Fusion Mechanism

SummaryIn flowering plants, fertilization-dependent degeneration of the persistent synergid cell ensures one-on-one pairings of male and female gametes. Here, we report that the fusion of the persistent synergid cell and the endosperm selectively inactivates the persistent synergid cell in Arabidopsis thaliana. The synergid-endosperm fusion causes rapid dilution of pre-secreted pollen tube attractant in the persistent synergid cell and selective disorganization of the synergid nucleus during the endosperm proliferation, preventing attractions of excess number of pollen tubes (polytubey). The synergid-endosperm fusion is induced by fertilization of the central cell, while the egg cell fertilization predominantly activates ethylene signaling, an inducer of the synergid nuclear disorganization. Therefore, two female gametes (the egg and the central cell) control independent pathways yet coordinately accomplish the elimination of the persistent synergid cell by double fertilization

IL-12 and IL-18 Induction and Subsequent NKT Activation Effects of the Japanese Botanical Medicine Juzentaihoto

In this study, we first measured some cytokine concentrations in the serum of patients treated with Juzentaihoto (JTT). Of the cytokines measured interleukin (IL) -18 was the most prominently up-regulated cytokine in the serum of patients under long term JTT administration. We next evaluated the effects of JTT in mice, focusing especially on natural killer T (NKT) cell induction. Mice fed JTT were compared to control group ones. After sacrifice, the liver was fixed, embedded and stained. Transmission electron microscope (TEM) observations were performed. Although the mice receiving the herbal medicine had same appearance, their livers were infiltrated with massive mononuclear cells, some of which were aggregated to form clusters. Immunohistochemical staining revealed that there was abundant cytokine expression of IL-12 and IL-18 in the liver of JTT treated mice. To clarify what the key molecules that induce immunological restoration with JTT might be, we next examined in vitro lymphocyte cultures. Mononuclear cells isolated and prepared from healthy volunteers were cultured with and without JTT. Within 24 hours, JTT induced the IL-12 and IL-18 production and later (72 hours) induction of interferon (IFN)-gamma. Oral administration of JTT may induce the expression of IL-12 in the early stage, and IL-18 in the chronic stage, followed by NKT induction. Their activation, following immunological restoration could contribute to anti-tumor effects

Dynamics of the cell fate specifications during female gametophyte development in Arabidopsis.

The female gametophytes of angiosperms contain cells with distinct functions, such as those that enable reproduction via pollen tube attraction and fertilization. Although the female gametophyte undergoes unique developmental processes, such as several rounds of nuclear division without cell plate formation and final cellularization, it remains unknown when and how the cell fate is determined during development. Here, we visualized the living dynamics of female gametophyte development and performed transcriptome analysis of individual cell types to assess the cell fate specifications in Arabidopsis thaliana. We recorded time lapses of the nuclear dynamics and cell plate formation from the 1-nucleate stage to the 7-cell stage after cellularization using an in vitro ovule culture system. The movies showed that the nuclear division occurred along the micropylar-chalazal (distal-proximal) axis. During cellularization, the polar nuclei migrated while associating with the forming edge of the cell plate, and then, migrated toward each other to fuse linearly. We also tracked the gene expression dynamics and identified that the expression of MYB98pro::GFP-MYB98, a synergid-specific marker, was initiated just after cellularization in the synergid, egg, and central cells and was then restricted to the synergid cells. This indicated that cell fates are determined immediately after cellularization. Transcriptome analysis of the female gametophyte cells of the wild-type and myb98 mutant revealed that the myb98 synergid cells had egg cell-like gene expression profiles. Although in myb98, egg cell-specific gene expression was properly initiated in the egg cells only after cellularization, but subsequently expressed ectopically in one of the 2 synergid cells. These results, together with the various initiation timings of the egg cell-specific genes, suggest complex regulation of the individual gametophyte cells, such as cellularization-triggered fate initiation, MYB98-dependent fate maintenance, cell morphogenesis, and organelle positioning. Our system of live-cell imaging and cell type-specific gene expression analysis provides insights into the dynamics and mechanisms of cell fate specifications in the development of female gametophytes in plants