Biology subjects

Naramoto, S.

Publications and source records attributed to Naramoto, S..

6 recordsLinked to original sources

bioRxiv2026

The Lateral Protein Cluster as a Key Component of Plant Cell Polarity

Cell polarity is an ancient organizing principle across kingdoms. As in animal epithelial cells, plant cells asymmetrically distribute proteins to establish functionally distinct membrane domains. In roots, radial polarity distinguishes inner and outer cell surfaces and supports directional nutrient transport, yet its molecular basis remains poorly understood. Here, we show that the leucine-rich repeat receptor-like kinases CaMRLK and IRK occupy complementary lateral plasma membrane domains in Arabidopsis thaliana roots. Polarity-guided proximity labeling identified previously uncharacterized proteins associated with inner- and outer-lateral domains. Clade VII LRR-RLKs, protein S-acyltransferases, SICK, IRKI1, and a distinct group of NPH3/RPT2-LIKEs assemble into the Lateral Protein Cluster (LPC) through multivalent interactions. LPC components are conserved across land plants, and disruption of NRL function impairs morphogenesis in Arabidopsis and Marchantia polymorpha. Together, these findings establish the LPC as an evolutionarily conserved molecular machinery linking radial cell polarity to plant morphogenesis.

plant biology↗

bioRxiv2023

Cytokinins specify pluripotent stem cell identity in the moss Physcomitrium patens

The shoot apical meristem (SAM) contains pluripotent stem cells that produce all the aerial parts of the plant. Stem cells undergo asymmetric cell divisions to self-renew and to produce differentiating cells. Our research focused on unraveling the mechanisms governing the specification of these two distinct cell fates following the stem cell division. For this purpose, we used the model organism Physcomitrium patens, which features a singular pluripotent stem cell known as the gametophore apical cell. We show that the activity of cytokinins, critical stem cell regulators, is restricted to the gametophore apical cell due to the specific localization of PpLOG, the enzyme responsible of cytokinin activation. In turn, PpTAW, which promotes differentiating cell identity of the merophyte, is excluded from the gametophore apical cell by the action of cytokinins. We propose a cytokinin-based model for the establishment of asymmetry in the pluripotent stem cell division. One Sentence SummaryCytokinins are confined to the pluripotent stem cells and exclude the differentiation factor TAW1 to establish the SAM from a single stem cell.

plant biology↗

bioRxiv2022

KARRIKIN INSENSITIVE2 (KAI2)-dependent signaling pathway controls vegetative reproduction in Marchantia polymorpha

In vegetative reproduction of Marchantia polymorpha, propagules, called gemmae, are formed in gemma cups. Despite its significance for survival, control of gemma and gemma cup formation by environmental cues is not well understood. We show here that the number of gemmae formed in a gemma cup is a genetic trait. Gemma formation starts from the central region of the floor of the gemma cup, proceeds to the periphery, and terminates when the appropriate number of gemmae are initiated. The MpKARRIKIN INSENSITIVE2 (MpKAI2)-dependent signaling pathway promotes gemma cup formation and gemma initiation. The number of gemmae in a cup is controlled by modulating the ON/OFF switch of the KAI2-dependent signaling. Termination of the signaling results in the accumulation of MpSMXL, a suppressor protein. In the Mpsmxl mutants, gemma initiation continues, leading to the formation of a highly increased number of gemmae in a cup. Consistent with its function, the MpKAI2-dependent signaling pathway is active in gemma cups where gemmae initiate, as well as in the notch region of the mature gemma and midrib of the ventral side of the thallus. In this work, we also show that GEMMA CUP-ASSOCIATED MYB1 works downstream of this signaling pathway to promote gemma cup formation and gemma initiation. We also found that the availability of potassium affects gemma cup formation independently from the KAI2-dependent signaling pathway in M. polymorpha. We propose that the ancestral function of the KAI2-dependent signaling pathway may be to optimize vegetative reproduction by adapting to the environment.

plant biology↗

bioRxiv2022

Contrasting and conserved roles of NPR proteins in diverged land plant lineages

The NPR proteins function as salicylic acid (SA) receptors in Arabidopsis thaliana. AtNPR1 plays a central role in SA-induced transcriptional reprogramming whereby positively regulates SA-mediated defense. NPRs are found in the genomes of nearly all land plants. However, we know little about the molecular functions and physiological roles of NPRs in most plant species. Our phylogenetic and alignment analyses show that Brassicaceae NPR1-like proteins have characteristically gained or lost functional residues or motifs identified in AtNPRs, pointing to the possibility of a unique evolutionary trajectory for the Brassicaceae NPR1-like proteins that has resulted in peculiar functions. In line with this observation, we find that the only NPR in Marchantia polymorpha, MpNPR, is not the master regulator of SA-induced transcriptional reprogramming and negatively regulates bacterial resistance in this species. Interspecies complementation analysis indicated that the molecular properties of AtNPR1 and MpNPR are partially conserved, implying the diversification of NPR-associated pathways contributed to distinct roles of NPR in different species. The Mpnpr transcriptome suggested potential roles of MpNPR in heat and far-red light responses. We identify both Mpnpr and Atnpr1-1 display enhanced thermomorphogenesis. NPRs and NPR-associated pathways clearly have evolved distinctively in diverged land plant lineages to cope with different terrestrial environments.

plant biology↗

bioRxiv2020

Major components in the KARRIKIN INSENSITIVE2-ligand signaling pathway are conserved in the liverwort, Marchantia polymorpha

KARRIKIN INSENSITIVE2 (KAI2) was first identified in Arabidopsis thaliana as a receptor of karrikin, a smoke-derived germination stimulant. KAI2 is also considered a receptor of an unidentified endogenous molecule called the KAI2-ligand (KL). Upon KAI2 activation, signals are transmitted through degradation of D53/SMXL proteins via ubiquitination by a Skp-Cullin-F-box (SCF) E3 ubiquitin ligase complex. All components in the KL signaling pathway exist in the liverwort Marchantia polymorpha, namely MpKAI2A and MpKAI2B, MpMAX2 encoding the F-box protein, and MpSMXL, indicating that the signaling pathway became functional in the common ancestor of bryophytes and seed plants. Genetic analysis using knock-out mutants of these KL signaling genes, produced using the CRISPR system, indicated that MpKAI2A, MpMAX2 and MpSMXL act in the same genetic pathway and control early gemma growth. Introduction of MpSMXLd53, in which a domain required for degradation is mutated, into wild-type plants caused phenotypes resembling those of the Mpkai2a and Mpmax2 mutants. In addition, Citrine fluorescence was detected in tobacco cells transiently transformed with the 35S:MpSMXL-Citrine gene construct and treated with MG132, a proteasome inhibitor. On the other hand, introduction of 35S:MpSMXLd53-Citrine conferred Citrine fluorescence without MG132 treatment. These findings imply that MpSMXL is subjected to degradation, and that degradation of MpSMXL is crucial for KL signaling in M. polymorpha. We also showed that MpSMXL is negatively regulated by KL signaling. Taken together, this study demonstrates that basic mechanisms in the KL signaling pathway are conserved in M. polymorpha.

plant biology↗

bioRxiv2019

Lateral organ diversification in plants mediated by the ALOG protein family of transcription factors

Land plant shoot structures evolved a diversity of lateral organs as morphological adaptations to the terrestrial environment, in which lateral organs independently evolved in each lineage in the sporophyte or gametophyte generation. The gametophyte meristem of the basally-diverging plant Marchantia polymorpha produces axes with non-photosynthetic scale-like lateral organs instead of leaves. Here we report that an ALOG (Arabidopsis LSH1 and Oryza G1) family protein in Marchantia, MpTAWAWA1 (MpTAW1), regulates meristem maintenance and lateral organ development. A mutation in MpTAW1, preferentially expressed in lateral organs, induces lateral organs with mis-specified identity and increased cell number, and furthermore, causes defects in apical meristem maintenance. Remarkably, MpTAW1 expression rescued the elongated-spikelet phenotype of a rice mutant of MpTAW1 homologue. This suggests that ALOG genes are co-opted to specify lateral organ identities in both gametophyte and sporophyte shoots by repressing lateral organ growth. We propose that the recruitment of ALOG-mediated lateral organ modification was in part responsible for the convergent evolution of independently-evolved lateral organs among highly divergent plant lineages and contributed to the morphological diversification of land plants.

plant biology↗