Biology subjects

Takahashi, N.

Publications and source records attributed to Takahashi, N..

42 records · Page 3Linked to original sources

bioRxiv2020

The Arabidopsis NRT1/PTR FAMILY Protein NPF7.3/NRT1.5 is an Indole-3-butyric Acid Transporter Involved in Root Gravitropism

Active membrane transport of plant hormones and their related compounds is an essential process that determines the distribution of the compounds within plant tissues and, hence, regulates various physiological events. Here, we report that the Arabidopsis NITRATE TRANSPORTER 1/PEPTIDE TRANSPORTER FAMILY 7.3 (NPF7.3) protein functions as a transporter of indole-3-butyric acid (IBA), a precursor of the major endogenous auxin indole-3-acetic acid (IAA). When expressed in yeast, NPF7.3 mediated cellular IBA uptake. Loss-of-function npf7.3 mutants showed defective root gravitropism with reduced IBA levels and auxin responses. Nevertheless, the phenotype was restored by exogenous application of IAA but not by IBA treatment. NPF7.3 was expressed in pericycle cells and the root tip region including root cap cells of primary roots where the IBA-to-IAA conversion occurs. Our findings indicate that NPF7.3-mediated IBA uptake into specific cells is required for the generation of appropriate auxin gradients within root tissues.

plant biology↗

bioRxiv2019

Perirhinal input to neocortical layer 1 controls learning

Signals sent back to the neocortex from the hippocampus control the long-term storage of memories in the neocortex1,2, but the cellular mechanisms underlying this process remain elusive. Here, we show that learning is controlled by specific medial-temporal input to neocortical layer 1. To show this we used direct cortical microstimulation detection task that allowed the precise region of learning to be examined and manipulated. Chemogenetically suppressing the last stage of the medial temporal loop, i.e. perirhinal cortex input to neocortical layer 1, profoundly disrupted early memory formation but had no effect on behavior in trained animals. The learning involved the emergence of a small population of layer 5 pyramidal neurons (~10%) with significantly increased firing involving high-frequency bursts of action potentials that were also blocked by suppression of perirhinal input. Moreover, we found that dendritic excitability was correspondingly enhanced in a similarly-sized population of pyramidal neurons and suppression of dendritic activity via optogenetic activation of dendrite-targeting inhibitory neurons also suppressed learning. Finally, single-cell stimulation of cortical layer 5 pyramidal neurons showed that burst but not regular firing retrieved previously learned behavior. We conclude that the medial temporal input to the neocortex controls learning through a process in L1 that elevates dendritic calcium and promotes burst firing.

neuroscience↗

bioRxiv2019

Epigenetic regulation of unique genes and repetitive elements by the KRAB zinc finger protein ZFP57

BackgroundKRAB-zinc finger proteins (KZFPs) represent one of the largest families of DNA binding proteins in vertebrate genomes and appear to have evolved to silence transposable elements (TEs) including endogenous retroviruses through sequence-specific targeting of repressive chromatin states. ZFP57 is required to maintain the post-fertilization DNA methylation memory of parental-origin at genomic imprints along with ZFP445 which is specific for imprints. However, ZFP57 has multiple methylated genomic targets. Here we conduct RNA-seq and ChIP-seq analyses in normal and ZFP57 mutant mouse ES cells to understand the relative importance of ZFP57 at unique and repetitive regions of the genome.\n\nResultsOver 80% of ZFP57 targets are TEs, however, ZFP57 is not essential for their repression. The remaining targets lie within unique imprinted and non-imprinted sequences. Though loss of ZFP57 influences imprinted genes as expected, the majority of unique gene targets lose H3K9me3 with little effect on DNA methylation and very few exhibiting alterations in expression. Comparison with DNA methyltransferase-deleted ES cells (TKO) identifies remarkably similar losses of H3K9me3 and changes in expression, defining regions where H3K9me3 is secondary to DNA methylation. We show that ZFP57 is the principal methylation-sensitive KZFP recruiting KAP1 and H3K9me3 in ES cells. Finally, like imprints, other unique targets of ZFP57 are enriched for germline-derived DNA methylation including oocyte-specific methylation that is resistant to post-fertilisation epigenetic reprogramming.\n\nConclusionOur analyses suggest the evolution of a rare DNA methylation-sensitive KZFP that is not essential for repeat silencing, but whose primary function is to maintain DNA methylation and repressive histone marks at germline derived imprinting control regions.

developmental biology↗

bioRxiv2019

A mobile ELF4 delivers circadian temperature information from shoots to roots

The circadian clock is synchronized by environmental cues, mostly by light and temperature. Elucidating how the plant circadian clock responds to temperature oscillations is crucial to understand plant responsiveness to the environment. Here we found a prevalent temperature-dependent function of the Arabidopsis clock component ELF4 (EARLY FLOWERING 4) in the root clock. Micrografting assays and mathematical analyses show that ELF4 moves from shoots to regulate rhythms in roots. ELF4 movement does not convey photoperiodic information but trafficking is essential to control the period of the root clock in a temperature-dependent manner. At low temperatures, ELF4 mobility is favored and results in a slow-paced root clock while high temperatures decrease movement, leading to a fast clock. Hence, the mobile ELF4 delivers temperature information and establishes a shoot-to-root dialogue that sets the pace of the clock in roots.

plant biology↗

bioRxiv2019

Stringent structural plasticity of dendritic spines revealed by two-photon glutamate uncaging in adult mouse neocortex in vivo

Two-photon uncaging of glutamate is widely utilized to characterize structural plasticity in brain slice preparations in vitro. In this study, we investigated spine plasticity by using, for the first time, glutamate uncaging in the neocortex of adult mice in vivo. Spine enlargement was successfully induced in a smaller fraction of spines in the neocortex (22%) than in young hippocampal slices (95%), even under a low magnesium condition. Once induced, the time course and mean amplitudes of long-term enlargement were the same (81%) as those in vitro. However, low-frequency (1-2 Hz) glutamate uncaging caused spine shrinkage in a similar fraction (34%) of spines as in vitro, but spread to the neighboring spines less frequently than in vitro. Thus, we found that structural plasticity can occur similarly in the adult neocortex in vivo as in the hippocampus in vitro, although it happens stringently in a smaller subset of spines.

neuroscience↗

bioRxiv2018

A regulatory module controlling stress-induced cell cycle arrest in Arabidopsis

Cell cycle arrest is an active response to stresses that enables organisms to survive under fluctuating environmental conditions. While signalling pathways that inhibit cell cycle progression have been elucidated, the putative core module orchestrating cell cycle arrest in response to various stresses is still elusive. Here we report that in Arabidopsis thaliana, the NAC-type transcription factors ANAC044 and ANAC085 are required for DNA damage-induced G2 arrest. Under genotoxic stress conditions, ANAC044 and ANAC085 enhance protein accumulation of the R1R2R3-type Myb transcription factor (Rep-MYB), which represses G2/M-specific genes. ANAC044/ANAC085-dependent accumulation of Rep-MYB and cell cycle arrest are also observed in the response to heat stress that causes G2 arrest, but not to osmotic stress that retards G1 progression. These results suggest that plants deploy the ANAC044/ANAC085-mediated signalling module as a hub which perceives distinct stress signals and leads to G2 arrest.

plant biology↗