Biology subjects

Yotsui, I.

Publications and source records attributed to Yotsui, I..

3 recordsLinked to original sources

bioRxiv2025

Humidity-driven ABA depletion determines plant-pathogen competition for leaf water

Bacterial phytopathogens, such as Pseudomonas syringae pv. tomato (Pst) DC3000, induce water-soaked lesions in the leaf apoplast under high humidity, facilitating infection. However, it remains largely unclear how plants regulate their resistance to restrict bacterial infection in response to humidity. Here, we demonstrate that abscisic acid (ABA)-catabolizing ABA 8-hydroxylase, encoded by CYP707A3, plays a critical role in this resistance in Arabidopsis thaliana. Elevated humidity induces CYP707A3 expression, which is essential for reducing ABA levels and promoting stomatal opening, thereby limiting bacterial water-soaking and infection following leaf invasion. High humidity also increases cytosolic Ca2+ levels via the Ca2+ channels CNGC2 and CNGC4, with partial involvement from CNGC9, activating the calmodulin-binding transcription activator CAMTA3 to drive CYP707A3 induction. However, Pst DC3000 counteracts this defense response using type III secretion effectors, particularly AvrPtoB, facilitating water-soaking. These findings provide insights into the mechanisms underlying the competition between plants and bacteria for leaf water under elevated humidity.

plant biology↗

bioRxiv2022

Genetic and phosphoproteomic basis of LysM-mediated immune signaling in Marchantia polymorpha highlights conserved elements and new aspect of pattern-triggered immunity in land plants

Pattern-recognition receptor (PRR)-triggered immunity (PTI) wards off a wide range of pathogenic microbes, playing a pivotal role in plant immunity. The model liverwort Marchantia polymorpha is emerging as a popular model for investigating the evolution of plant-microbe interactions. M. polymorpha triggers defense-related gene expression upon sensing components of bacterial and fungal extracts, suggesting the existence of PTI in this plant model. However, the molecular components of the putative PTI in M. polymorpha have not yet been described. We show that, in M. polymorpha, which has four LysM receptor homologs, lysin motif (LysM) receptor-like kinase (LYK) MpLYK1 and LYK-related (LYR) MpLYR are required for sensing chitin and peptidoglycan fragments, triggering a series of characteristic immune responses. Comprehensive phosphoproteomic analysis of M. polymorpha in response to chitin treatment identified regulatory proteins that potentially shape LysM-mediated PTI. The identified proteins included homologs of well-described PTI components in angiosperms as well as proteins whose roles in PTI are not yet determined, including the blue-light receptor phototropin MpPHOT. We revealed that MpPHOT is required for a negative feedback of defense-related gene expression during PTI. Taken together, this study outlines the basic framework of LysM-mediated PTI in M. polymorpha and demonstrates the utility of M. polymorpha as a plant model for discovering novel or fundamental molecular mechanisms underlying PRR-triggered immune signaling in plants.

plant biology↗

bioRxiv2020

Activation of SnRK2 by the Raf-like kinase ARK represents a common mechanism of ABA response in embryophytes

The Raf-like protein kinase ARK previously identified in the moss Physcomitrella patens acts as an upstream regulator of subgroup III SnRK2, the key regulator of abscisic acid (ABA) and abiotic stress responses. However, the mechanisms underlying activation of ARK by ABA and abiotic stress for the regulation of SnRK2 including the role of ABA receptor-associated group A PP2C (PP2C-A) are not understood. We identified Ser1029 as the phosphorylation site in the activation loop of ARK, which provided a possible mechanism for regulation of its activity. Analysis of transgenic ark lines expressing ARK-GFP with Ser1029-to-Ala mutation indicated that this replacement causes reductions in ABA-induced gene expression, stress tolerance and SnRK2 activity. Immunoblot analysis using an anti-phosphopeptide antibody indicated that ABA treatments rapidly stimulate Ser1029 phosphorylation in wild type. The phosphorylation profile of Ser1029 in ABA-hypersensitive ppabi1 lacking PP2C-A was similar to that in wild type, whereas little Ser1029 phosphorylation was observed in ABA-insensitive ark missense lines. Furthermore, newly isolated ppabi1 ark lines showed ABA-insensitive phenotypes similar to those of ark lines. These results indicate that ARK is a primary activator of SnRK2, preceding negative regulation by PP2C-A in bryophytes, which provides a prototypal mechanism for ABA and abiotic stress-responses in embryophytes. One sentence summaryPhysiological characterization of various moss mutants revealed a common mechanism for phytohormone responses under water deficit in all land plants.

plant biology↗