Jul 2026· New Phytologist· Vol 251, pp. 3347-3366· 0 citations· 118 references
Medicine
TL;DR
The findings demonstrate the presence of a functional SnRK2 pathway in a chlorophyte alga, suggesting that core components were established early in the green lineage and underscores the need for broader taxonomic sampling to reconstruct the ancestral signaling networks underlying stress adaptation.
Abstract
The SNF1‐related protein kinase 2 (SnRK2) pathway is a central regulator of abiotic stress signaling in land plants, yet its evolutionary origins and functional conservation across the green lineage remain poorly understood. To determine whether this signaling module predates the streptophyte–chlorophyte divergence, we investigated the chlorophyte alga Chlamydomonas reinhardtii, which diverged from the streptophyte lineage over 1 billion years ago. Using a combination of reverse genetics and protein–protein interaction assays, we identified and characterized a bona fide SnRK2 signaling module in C. reinhardtii. We demonstrate that the isoform SnRK2.7 is essential for osmotic stress tolerance and general cellular viability. SnRK2.7 localizes to the contractile vacuole, an osmoregulatory organelle lost during streptophyte evolution, revealing a lineage‐specific functional adaptation. Together with MAPKKK3, a B1/B3‐RAF kinase, and the clade A protein phosphatase PP2C3, these components constitute a MAPKKK3‐SnRK2.7‐PP2C3 regulatory module in C. reinhardtii. Our findings demonstrate the presence of a functional SnRK2 pathway in a chlorophyte alga, suggesting that core components were established early in the green lineage. This work provides a foundation for comparative studies across green plants and underscores the need for broader taxonomic sampling to reconstruct the ancestral signaling networks underlying stress adaptation.
Sucrose non-fermenting-1-related protein kinase (SnRK) is a plant serine/threonine kinase that mediates stress signaling, yet its function in the mangrove Avicennia marina remains unexplored. In this study, we identified 46 SnRK genes in A. marina, classifying them into three subfamilies with high phylogenetic conservation. Family expansion occurred mainly through 20 segmental duplication events under purifying selection (Ka/Ks < 1). Promoter regions were enriched in stress- and hormone-responsive elements, and expression profiling showed distinct tissue-specific and stress-responsive patterns. Our study specifically focused on the functional characterization of AmSnRK2.7. AmSnRK2.7-overexpressed Arabidopsis thaliana increases salt tolerance by altering the expression of ion transport genes and mediating Na+ efflux from the roots. Further investigation revealed that AmSnRK2.7 interacts with and phosphorylates AmENO2 (enolase, a key enzyme in the glycolysis pathway). Meanwhile, measurements of ATP content in wild type, AmSnRK2.7-overexpressed Arabidopsis lines and the atsnrk2.6 (homologous gene of AmSnRK2.7 in A. thaliana) mutant confirm that the AmSnRK2.7-AmENO2 module can affect the energy-driven Na+ efflux. Our findings provide key insights into the role of SnRK gene family in mangrove adaptation to saline intertidal habitat, and suggest AmSnRK2.7-AmENO2 module plays a role in salt tolerance.
Jin-Yu Liu, Yudan Xiang, Lingyu Song et al.· Plant, Cell and Environment· 0 citations
ABSTRACT Canonical partner-switching systems (PSSs) regulate sigma factor activity through reversible phosphorylation, but their established roles have been largely limited to stress responses and sporulation in Firmicutes. Whether this regulatory mechanism also controls developmental cell fate decisions in other bacterial phyla has remained unknown. Here, we identify a canonical PSS that governs heterocyst differentiation in the multicellular cyanobacterium Anabaena sp. PCC 7120. This system comprises the anti-sigma factor All2284 (NfsS) and the anti-anti-sigma factor All2283 (NfsR). Structural predictions and biochemical assays showed that NfsS phosphorylates NfsR on a conserved serine residue, whereas bacterial two-hybrid and co-purification assays demonstrated that NfsS binds the developmental sigma factors SigC and SigE. Deletion of nfsR abolished heterocyst formation and diazotrophic growth, and transcriptomic analysis revealed broad failure to induce late heterocyst genes, including nitrogen fixation functions such as nifHDK and fdxH. Phylum-wide comparative genomics further showed that PSS genes and putative functional clusters are strongly enriched in filamentous and heterocyst-forming taxa, indicating an association between the expansion of these signaling modules and the emergence of multicellularity and developmental specialization. Together, these findings establish a PSS as a direct regulator of terminal cell differentiation in a gram-negative bacterium and reveal partner switching as a conserved regulatory principle linking environmental signaling to developmental fate in a major bacterial phylum. IMPORTANCE While partner-switching systems are classically associated with stress responses and sporulation control in Firmicutes, whether this regulatory logic governs developmental decisions in other bacterial phyla has remained unknown. Here, we establish that a related partner-switching mechanism operates in a distinct bacterial lineage, the cyanobacteria, where it controls a major developmental transition involving terminal cell differentiation. Specifically, we show that a phosphorylation-dependent checkpoint involving the anti-sigma factor NfsS and the anti-anti-sigma factor NfsR directly regulates heterocyst formation. Disruption of this switch abolishes cell differentiation and diazotrophic growth, revealing that this system is an obligate gatekeeper for terminal differentiation. Conceptually, these findings substantially extend the known functional repertoire of partner-switching circuits: rather than controlling stress adaptation or spore dormancy, this module has been co-opted to govern a complex, multicellular developmental program in an organism that underpins global carbon and nitrogen cycles. This work, therefore, establishes a new paradigm for phosphorylation-based control of developmental sigma factors and provides a tractable model for dissecting how conserved signaling modules are rewired to drive lineage-specific innovations across the bacterial domain. While partner-switching systems are classically associated with stress responses and sporulation control in Firmicutes, whether this regulatory logic governs developmental decisions in other bacterial phyla has remained unknown. Here, we establish that a related partner-switching mechanism operates in a distinct bacterial lineage, the cyanobacteria, where it controls a major developmental transition involving terminal cell differentiation. Specifically, we show that a phosphorylation-dependent checkpoint involving the anti-sigma factor NfsS and the anti-anti-sigma factor NfsR directly regulates heterocyst formation. Disruption of this switch abolishes cell differentiation and diazotrophic growth, revealing that this system is an obligate gatekeeper for terminal differentiation. Conceptually, these findings substantially extend the known functional repertoire of partner-switching circuits: rather than controlling stress adaptation or spore dormancy, this module has been co-opted to govern a complex, multicellular developmental program in an organism that underpins global carbon and nitrogen cycles. This work, therefore, establishes a new paradigm for phosphorylation-based control of developmental sigma factors and provides a tractable model for dissecting how conserved signaling modules are rewired to drive lineage-specific innovations across the bacterial domain.
Stéphanie Champ, Eva Furet, Frédérique Pompeo et al.· mBio· 0 citations
Insight is provided into the regulatory roles of PP2A regulatory subunit SsRts1 in S. scitamineum, and the understanding of PP2A function in plant-pathogenic fungi is expanded.
Jinfeng Qiu, Hao-Ming Wu, Ying Liu et al.· Virulence· 0 citations
Eukaryotic translation initiation factor 5A (eIF5A) is a highly conserved protein family unique to eukaryotes, yet its functional characterization in woody plants remains limited. In this study, we identified four eIF5A genes (PtoeIF5A1–PtoeIF5A4) from the genome of Populus tomentosa, a fast-growing tree species indigenous to China, and characterized their expression patterns and functional roles through bioinformatics analysis, quantitative real-time PCR, stable overexpression in Arabidopsis thaliana, and transient expression in Nicotiana benthamiana leaves. Our results demonstrated that all PtoeIF5A proteins contain a conserved OB-fold domain and multiple phosphorylation sites, with PtoeIF5A1 showing predominant expression in roots and secondary xylem. Functional assays revealed that PtoeIF5A1 overexpression accelerated inflorescence stem elongation and early flowering in Arabidopsis, induced visible chlorosis and programmed cell death (PCD) in tobacco leaves, and significantly enhanced salt tolerance under NaCl treatment. Collectively, these findings establish PtoeIF5A1 in poplar as a pleiotropic regulator integrating developmental cues, programmed cell death, and stress responses; and as a valuable genetic resource for breeding stress-resilient woody plants.
Dan Zhu, Y. Guan, Feng Feng et al.· Plants· 0 citations
Oxysterol-binding protein (OSBP)-related proteins (ORPs) are indispensable eukaryotic lipid transporters and promising targets for pharmaceutical and agrochemical exploitation. Among ORP family members across kingdoms, oomycete ORP1 constitutes a phylogenetically distinct subtype that evolved independently in oomycetes, which is markedly divergent from ORP homologues in animals, plants and fungi. Oxathiapiprolin, the first commercial fungicide targeting OSBP family proteins, specifically acts on oomycete ORP1 and exhibits robust inhibitory efficacy against diverse Phytophthora pathogens and downy mildews. Nevertheless, the molecular function of oomycete ORP1 and the inhibitory mechanism of oxathiapiprolin remain poorly defined. Here, we demonstrate that PsORP1 of Phytophthora sojae specifically localises to ER-Golgi membrane contact sites (MCSs) and is indispensable for vegetative growth and asexual/sexual development of P. sojae. In vitro liposome reconstitution assays confirmed that the conserved C-terminal OSBP-related domain (ORD) of PsORP1 mediates canonical phosphatidylserine (PS)/phosphatidylinositol 4-phosphate (PI4P) counter-transport. Biochemical binding assays further verified that oxathiapiprolin directly interacts with the ORD of PsORP1 and competitively blocks PS/PI4P lipid exchange. Collectively, this study demonstrates that PsORP1 localises to ER-Golgi MCSs and mediates ORD-dependent PS/PI4P counter-transport, which is essential for P. sojae development, and elucidates that oxathiapiprolin directly targets the ORD to competitively block this lipid exchange, providing a structural framework for rational design of next-generation OSBP-targeting inhibitors against oomycetes.
