Biology subjects

Theumer, M.

Publications and source records attributed to Theumer, M..

4 recordsLinked to original sources

bioRxiv2025

The interplay between autophagy and the carbon/nitrogen ratio as key modulator of the auxin-dependent chloronema-caulonema developmental transition in Physcomitrium patens.

Plants, as sessile living systems, have the capacity to respond to both internal and external signals by modulating their growth and developmental programs. Autophagy is a recycling process which is known to respond to these signals, yet its role as an integrative regulatory node coordinating environmental inputs and developmental outputs remains underexplored, particularly outside model angiosperms like Arabidopsis thaliana. Here, we investigate how the fluctuating supply of carbon and nitrogen modulates autophagy in relation to the auxin-driven chloronema-to-caulonema transition in the bryophyte Physcomitrium patens. We show that autophagy-deficient mutants display a loss of coordinated plasticity in response to the changing C/N supply ratio, exhibiting an initially enhanced yet ultimately unsustainable response to nitrogen deficiency alongside attenuated responses to external sucrose. These altered responses reflect a modified basal state in the mutants, evidenced by higher intrinsic caulonemal growth, sucrose accumulation, altered auxin homeostasis, and differential auxin-related gene expression. Consistent with this, exogenous auxin elicits a diminished developmental response but accelerates senescence in the mutants. Finally, we demonstrate how autophagic flux is dynamically modulated by the C/N supply ratio and show that it is activated when this ratio is most unbalanced. We propose that high autophagic activity is associated with chloroplast-rich chloronemal cells, whereas caulonemata-inducing conditions decrease autophagic flux. This implies a cell-type-specific modulation of autophagy, where it is negatively correlated with caulonemal development. Together, our findings identify autophagy as a key regulator within the system that modulates ordered and adaptive responses to both external nutrient availability and internal hormonal signaling. HIGHLIGHTSAutophagy coordinates carbon/nitrogen supply with developmental programs in P. patens. Autophagy negatively correlates with auxin-driven caulonemal development. Autophagy-deficient mutants lose coordinated plasticity. atg mutants exhibit a modified basal state with altered sugar and auxin profiles.

plant biology↗

bioRxiv2025

Phosphoinositide-specific Phospholipase C 2 (SlPLC2) Facilitates Vesicle Formation and Modulates Immune Signaling in Tomato Phytophthora infestans Interactions

Phosphoinositide-specific phospholipase C (PI-PLC) is a signaling enzyme that hydrolyzes membrane phosphoinositide to generate lipid- and lipid-derived second messengers. In plants, PI-PLCs have been implicated in various physiological processes, including immunity. Tomato SlPLC2 was previously shown to be implicated in susceptibility to the necrotrophic fungus Botrytis cinerea. However, whether this observation extends to pathogens with different lifestyles and evolutionary origins, remains unknown. Here, we investigated SlPLC2 function during infection with Phytophthora infestans, a globally devastating oomycete and causal agent of potato and tomato late blight. CRISPR-Cas9 knockout SlPLC2 plants showed significantly reduced disease symptoms, lower pathogen biomass, and decreased sporangia production, indicating impaired colonization. Upon infection, SlPLC2 knockout lines displayed attenuated expression of salicylic acid (SA)- and jasmonic acid (JA)-responsive genes suggesting disrupted hormone signaling. Consistent with PLC role during plant defense, early immune responses such as hydrogen peroxide accumulation and callose deposition were reduced in knockout plants. At the cellular level, these plants allow fewer infection vesicles formation by P. infestans, accompanied by an increase in expression of a biotrophy-associated effector gene PiAvrblb2, suggesting impaired establishment of infection. In Nicotiana benthamiana SlPLC2-GFP localizes predominantly at the plasma membrane. Upon P. infestans inoculations, SlPLC2-GFP localizes to the membrane surrounding infection vesicles, where we also detected phosphoinositides PI4P and PI(4,5)P2. Overexpression of SlPLC2 in Nicotiana benthamiana enhanced susceptibility to P. infestans, reinforcing its positive role in colonization. Together, these findings identify SlPLC2 as a susceptibility factor associated with enhanced P. infestans colonization. StatementThis study identifies SlPLC2 as a key susceptibility factor that supports Phytophthora infestans infection by coordinating vesicle formation and early immune responses in tomato.

plant biology↗

bioRxiv2022

Autophagy modulates apical growth and development in the moss Physcomitrium patens

Different to root hairs and pollen tubes, Physcomitrium patens apical growing protonemal cells have the singularity that they continue to undergo cell divisions as the plant develops, allowing to study autophagy in the context of a multicellular apical growing tissue coupled to development. Herein, we showed that the core autophagy machinery is present in the moss P. patens, and deeply characterized the growth and development of wild-type, atg5 and atg7 loss-of-function mutants under optimal and nutrient-deprived conditions. Our results showed that the growth of the different morphological and functional protonemata apical growing cells, chloronema and caulonema, is differentially modulated by this process. These differences depend on the protonema cell type and position along the protonemal filament, and growth condition. As a global plant response, the absence of autophagy triggers the spread of the colony through protonemata growth at the expense of a reduction in buds and gametophore development, and thus the adult gametophytic and reproductive phases. Altogether this study provides valuable information indicating that autophagy has roles during apical growth with differential responses within the cell types of the same tissue and contributes to life cycle progression and thus the development of the 2D and 3D tissues of P. patens. HIGHLIGHTAutophagy is differentially induced in protonemal cells, and contributes to apical growth, life cycle progression, and thus the development of the 2D and 3D tissues of P. patens.

plant biology↗

bioRxiv2019

Different salicylic and jasmonic acids imbalances are involved in the oxidative stress-mediated cell death, induced by fumonisin B1 in maize seedlings with contrasting resistance to Fusarium verticillioides ear rot in the field.

Background and aimFungal and plant secondary metabolites modulate the plant-pathogen interactions. However, the participation of fumonisins in the Fusarium verticillioides-maize pathosystem is unclear. In this work was studied the cell death, and the reactive oxygen species (ROS) - phytohormone imbalance interplay underlying the phytotoxicity of fumonisin B1 (FB1) in maize germplasms with contrasting resistance to Fusarium ear rot in the field. MethodsResistant (RH) and susceptible hybrid (SH) maize seedlings, grown from uninoculated seeds irrigated with FB1 (1 and 20 ppm), were harvested at 7, 14 and 21 days after planting, and were examined for electrolyte leakage (aerial parts); and for oxidative stress biomarkers (aerial parts and roots). The phytohormone (salicylic and jasmonic acids) imbalance interplay underlying the FB1-induced cell death were further explored in seedlings exposed 24 h to the mycotoxin (1 ppm) in hydroponics. ResultsCell death increased in RH and SH watered with 1 and 20 ppm of mycotoxin, respectively. Both toxin concentrations were pro-oxidant, and the major perturbations were found in roots. An Integrated Biomarker Response index was calculated suggesting that phytotoxicity occurs in a redox context more efficiently controlled by RH. ConclusionThe pre-treatment with the antioxidant ascorbic acid led to the conclusion that cell death in RH was related to a salicylic acid increase mediated by ROS. Nevertheless, FB1 induced two different phytohormonal regulatory mechanisms mediated by oxidative stress in both maize hybrids.

plant biology↗