Plant Physiology最新文献

Plant small secreted peptides (SSPs) are involved in numerous developmental processes and adaptive plant responses. These include root development, immunity, and symbiotic relationships in herbaceous plants; three processes crucial for establishing functional ectomycorrhizal associations in trees. While fungal SSPs involved in ectomycorrhizal establishment have been identified, the role of plant SSPs remains largely unexplored. Although thousands of SSPs have been predicted in plant genomes, their small size and high sequence divergence hinder accurate automated annotation. To address this issue, we combined de novo gene prediction with a family-specific motif search to identify 1,053 SSPs from 21 symbiosis-related families in the genomes of two ectomycorrhizal (ECM) tree species: poplar (Populus trichocarpa) and English oak (Quercus robur). Nearly half of these SSPs, which included signaling, antimicrobial, and peptidase inhibitor peptides, were transcriptionally regulated during ectomycorrhizal symbiosis with various fungal partners, implying that SSPs involved in ECM symbiosis support a diversity of functions. Five ectomycorrhizal-responsive CLAVATA3/EMBRYO SURROUNDING REGION-related (CLE) peptides from poplar enhanced ectomycorrhizal root formation in functional assays. These peptides, which belong to CLE clades associated with meristematic activity, are phylogenetically distinct from CLEs involved in the autoregulation of arbuscular mycorrhizal and rhizobial symbioses, indicating that poplar co-opted a distinct set of SSPs for ECM development. The activity of these peptides did not increase lateral root number but inhibited adventitious and lateral root growth, suggesting their role in promoting ectomycorrhizal root organogenesis. Our results expand the understanding of host tree contributions to ectomycorrhizal development and identify a set of candidate SSPs for future functional studies, thereby highlighting a previously uncharacterized layer of regulation in tree-fungi mutualism.

L-lysine (Lys) has been explored as a potential cyanobactericide due to its inhibitory effects on cyanobacterial growth at micromolar concentrations, comparable to many antibiotics. Here, we investigated the early metabolic and physiological responses of the model cyanobacterium Synechocystis sp. PCC 6803 to Lys exposure. Physiological analyses revealed cell enlargement, oxidative stress, and photosynthesis inhibition, leading to growth arrest. Metabolomic profiling indicated disruptions in peptidoglycan biosynthesis, evidenced by the accumulation of L-/D-alanine, meso-diaminopimelate, and D-Ala-D-Ala, suggesting interference with cell wall integrity. Furthermore, levels of energy metabolites and other amino acids, including tyrosine, tryptophan, valine, and iso-/leucine, were significantly altered, implying broader metabolic impacts of Lys toxicity. To explore potential resistance mechanisms, we used a CRISPRi-based genetic screen to identify key genes involved in relieving Lys toxicity. The Bgt permease system, responsible for basic amino acid uptake, was essential for acquiring Lys resistance, as a bgtA mutant exhibited normal growth on elevated Lys concentrations, thereby validating our CRISPRi screen. Additionally, UirR, a DNA-binding response regulator, and genes linked to c-di-AMP signaling, seemed implicated in Lys metabolism. Deletion of the c-di-AMP synthase gene increased Lys sensitivity, supporting a role for c-di-AMP in cell wall homeostasis and osmotic stress regulation. Altogether, our findings explored the early metabolic responses and physiological consequences of Lys exposure in Synechocystis, demonstrating its effects on peptidoglycan biosynthesis, amino acid metabolism, and nucleotide biosynthesis. This, as well as the identification of key genetic factors contributing to Lys resistance, provides insights into cyanobacterial physiology and the potential application of Lys in bloom-control strategies.

Light and subterranean darkness play a crucial role in early plant development to guide seamless progression from a dormant seed to a well-established seedling. In seed plants crosstalk between light and hormone signaling pathways optimizes seed germination. This is followed by etiolated growth characterized by the formation of a long hypocotyl and closed cotyledons forming the apical hook. These etiolated structures facilitate the efficient emergence of seedlings from underneath the soil. Upon emergence, exposure to light promotes the de-etiolation process, characterized by inhibition of hypocotyl elongation and formation of open and green cotyledons. The early developmental steps in a plant's life-cycle, which include seed germination and post-germinative seedling establishment, are the most stress-sensitive stages. To acclimatize with the changing environment plants must activate stress-resilience pathways. Recent studies shed light on how light- and dark-regulated factors modulate responses to combat various abiotic stresses, including high temperature, high-intensity light, UV-B radiation, and salinity stress. Plant biologists have traditionally examined plant-environment interactions utilizing two complementary but distinct approaches. Developmental biology has focused on the interplay of external influences such as light, temperature, and endogenous cues like phytohormones to modulate plant development. Stress biology, in contrast, has studied how various physiological and molecular processes are regulated in response to environmental stress and lead to the plant's ability to adapt. Here we link these two concepts by demonstrating how light-controlled developmental programs are tightly connected to stress-responsive pathways. These interconnected systems provide flexibility and resilience to plants to survive and evolve under dynamic environments.

How nuclear condensates encode cell-signaling dynamics remains unclear. Photobodies (PBs) in Arabidopsis offer a genetically tractable paradigm. PBs are light- and temperature-sensing nuclear condensates organized by the thermosensitive photoreceptor phytochrome B (phyB). Recent advances have clarified PB composition and illuminated PB formation and function. PhyB is the dominant component and provides scaffold-like determinants that recruit selective signaling partners as primary clients (direct phyB binders) and secondary clients (recruited via primaries), spanning transcription/splicing regulators, E3-ligase components, kinases/phosphatases, and chaperones. These clients connect phyB condensates to diverse environmental and hormonal pathways, positioning PBs as a central hub for signaling integration. PB assembly is driven by condensation encoded in phyB's output module and modulated by its photosensory module, coupling assembly/dissolution to photostate and temperature. PBs nucleate nonrandomly at preferred seeding sites, producing spatially distinct classes with different occurrence frequencies and thermosensitivities. PB formation partitions signaling between PBs and the surrounding nucleoplasm, establishing a two-compartment photosensory system. Within this architecture, dynamic sequestration in PBs tunes nucleoplasmic transcription-factor stability and activity to expand signaling dynamic range and extends phyB control into the night by stabilizing active phyB. We propose that PBs function as an autoregulatory rheostat, dialing nucleoplasmic light sensitivity in proportion to incident irradiance and thereby enabling continuous discrimination of light-intensity changes across multiple orders of magnitude. We suggest that this two-compartment logic illustrates a general role of membraneless organelles in signaling: using dense-phase dynamics to adjust pathway sensitivity and output in the surrounding dilute phase.