Biology subjects

Kato, C.

Publications and source records attributed to Kato, C..

4 recordsLinked to original sources

bioRxiv2026

Calcium Dynamics During Pollen Tube Reception in Arabidopsis Ovules

In flowering plants, pollen tubes communicate with ovular cells to achieve precise one-to-one pollen tube reception. The final step of this communication between the pollen tube and synergid cells has been extensively investigated and visualized by calcium imaging. Synergid cells exhibit characteristic cytoplasmic calcium concentration oscillations, which are thought to play a critical role in pollen tube reception. However, their significance and relationship with calcium dynamics in the entire ovule remain unclear. Here, we show, using the calcium sensor GCaMP6s, that proteins involved in asparagine-linked glycosylation (N-linked glycosylation) are required for normal calcium oscillations in synergid cells but are not essential for pollen tube reception. Using a semi-in vivo assay in Arabidopsis thaliana, we found that the amplitude of these oscillations prior to rapid pollen tube growth across the filiform apparatus was reduced in mutants lacking the oligosaccharyltransferase (OST) 3/6 subunit or alpha1,2-glucosyltransferase (ALG) 10, both of which are involved in N-linked glycosylation. Notably, these mutants did not exhibit reduced fertility attributable to defects in the female gametophyte but instead showed a polytubey phenotype due to a sporophytic defect. These findings suggest that N-linked glycans mediate communication between synergid cells and the pollen tube and indicate that the typical pattern of calcium oscillations in synergid cells is not essential for triggering pollen tube rupture. Furthermore, we show that sporophytic tissues of the ovule exhibit calcium waves that propagate toward the funiculus in correlation with pollen tube contact and rupture, implying that ovular tissues can potentially transmit these signals distantly beyond the ovule. Together, these findings reveal previously unrecognized intercellular calcium signaling and its significance in pollen tube reception by the ovule.

plant biology↗

bioRxiv2025

Genetic basis of R-phase H:z27 antigen expression and phylogenetic relationships of Salmonella enterica serovar Senftenberg

Salmonella enterica serovar Senftenberg (S. Senftenberg) is one of the most prevalent Salmonella serovars and can be isolated from various animals and humans. According to the White-Kauffmann-Le Minor (WKL) scheme, the antigenic formula of S. Senftenberg is defined as 1,3,19:g,[s],t:-. Although the antigenic formula 1,3,19:z27:- was formerly designated as serovar Simsbury, this name was later removed from the WKL scheme due to reports of interconvertibility between serovars Senftenberg and Simsbury. The H:z27 antigen is currently recognized as one of the R-phase H antigens of S. Senftenberg. To elucidate the genetic basis of H:z27 antigen expression in S. Senftenberg, we determined the whole-genome sequences of isolates expressing the H:z27 antigen. These isolates belonged to sequence type (ST) 185 and harbored a horizontally acquired chromosomal region containing the fljA, fljB, and pinR genes, which are predicted to encode a translational repressor of fliC mRNA, a phase 2 flagellin, and an invertase, respectively. A deletion mutant lacking this region expressed the H:g,s,t antigen instead of H:z27, as confirmed by serotyping and Western blot analysis. Phylogenetic analysis based on S. Senftenberg genome archives, together with the sequences obtained in this study, suggested that the S. Senftenberg ST185 lineage acquired the fljAB-pinR locus around 1867. In contrast, our broader phylogenetic analysis of Salmonella serovars indicated that S. Senftenberg ST14 is genetically closer to certain other serovars than to ST185, while ST185 shows a closer relationship to a different serovar than to ST14. These findings suggest that S. Senftenberg comprises at least two distinct genomic lineages. IMPORTANCELimited information is available on the genetic basis of R-phase H antigen expression in S. enterica. In this study, we first demonstrated that the R-phase H:z27 antigen of S. Senftenberg is determined by a horizontally acquired chromosomal region. The ST 185 lineage of S. Senftenberg appears to have acquired this chromosomal region around 1867 and subsequently disseminated worldwide. We also demonstrated that S. Senftenberg comprises at least two distinct genomic lineages. The combined use of serotyping and multilocus sequence typing may provide a typing framework that better reflects the disease potential of Salmonella.

microbiology↗

bioRxiv2023

PKCdelta splicing variant (PKCdeltaIII) induces neurite outgrowth in PC12 cells in the absence of NGF

Protein kinase C (PKC){delta} is a serine/threonine kinase involved in many cellular processes in response to diverse stimuli, including cell proliferation, differentiation, apoptosis, tumor inhibition, and cell migration. PKC{delta} consists of the N terminal regulatory domain and the C terminal catalytic domain, which are linked with a hinge region. An alternative splicing variant of rat PKC{delta} (also known as PKC{delta}III) has been reported, and this PKC{delta} splicing variant (SV) has only the regulatory domain without the catalytic domain. However, its function remains unclear. In this study, we found that PKC{delta} SV induced neurite outgrowth in the absence of nerve growth factor (NGF) in PC12 cells. Immunoblot analysis revealed that ERK was phosphorylated by NGF treatment, but not by PKC{delta} SV induction, indicating that PKC{delta} SV-mediated neurite outgrowth was different from NGF-mediated one. In addition, we showed that PKC{delta} full length and SV increased their mRNA expression after NGF treatment and that PKC{delta} SV was more susceptible to its proteasomal degradation. Our findings provided insights into the role of PKC{delta} SV in neurite outgrowth.

neuroscience↗

bioRxiv2019

Nucleosides drive histiocytosis in SLC29A3 disorders by activating TLR7

A lysosomal transmembrane protein SLC29A3 transports nucleosides from lysosomes to the cytoplasm. Loss-of-function mutations of the SLC29A3 gene cause lysosomal nucleoside storage in monocyte/macrophages, leading to their accumulation called histiocytosis in humans and mice. Little is known, however, about a mechanism behind nucleoside-dependent histiocytosis. TLR7, an innate immune sensors for single stranded RNA, bind and respond to nucleosides. We here show that they drive nucleoside-mediated histiocytosis. Patrolling monocyte/macrophages accumulate in the spleen of Slc29a3-/- mice but not Slc29a3-/- Tlr7-/- mice. Accumulated patrolling monocyte/macrophages stored nucleosides derived from cell corpse. TLR7 was recruited to phagosomes and activated as evidenced by TLR7-dependent phagosomal maturation. TLR7 induced hyper-responsiveness to M-CSF in Slc29a3-/- monocyte/macrophages. These results suggest that TLR7 drives histiocytosis in SLC29A3 disorders. One Sentence SummarySLC29A3 disorders are caused by activation of TLR7 with accumulated nucleosides in lysosomes.

immunology↗