Biology subjects

Augstein, F.

Publications and source records attributed to Augstein, F..

5 recordsLinked to original sources

bioRxiv2024

MEDIATOR SUBUNIT 25 modulates ERFVII-controlled hypoxia responses in Arabidopsis

Flooding impairs plant growth through oxygen deprivation, which activates plant survival and acclimation responses. Low-oxygen responses are generally associated with activation of group VII ETHYLENE-RESPONSE FACTOR (ERFVII) transcription factors. However, mechanism and molecular components by which ERFVII factors initiate gene expression are not fully elucidated. Here, we show that the Mediator complex subunit AtMED25 is recruited by RELATED TO APETALA 2.2 (RAP2.2) and RAP2.12 to coordinate gene expression during hypoxia in Arabidopsis thaliana.. The med25 mutants display reduced low-oxygen stress tolerance. AtMED25 associates with several ERFVII-controlled hypoxia core genes and its loss impairs transcription under hypoxia due to decreasing RNA polymerase II recruitment. Protein complex pulldown assays demonstrate that the Mediator complex built around AtMED25 is adjusted under low-oxygen conditions. Moreover, during hypoxia, no functional cooperation between AtMED25 and the two subunits AtMED8 and AtMED16 occurs, contrasting previous observations made for other conditions. In addition, AtMED25 function under hypoxia is independent from ethylene signalling. Finally, a functional conservation at the molecular level was found for the MED25-ERFVII module between Arabidopsis thaliana and the monocot Oryza sativa, pointing to a potentially universal role of MED25 in enabling ERFVII-dependent transcript responses to hypoxia in plants.

plant biology↗

bioRxiv2022

Salinity induces discontinuous protoxylem by a DELLA-dependent mechanism promoting salt tolerance in Arabidopsis seedlings

O_LISalinity is detrimental to plants and developmental adjustments limiting salt uptake and transport is therefore important for acclimation to high salt. These parameters may be influenced by xylem morphology, however, how plant root xylem development is affected by salt stress remains unclear. C_LIO_LIThrough detailed phenotypic analyses, molecular and genetic techniques, we demonstrate that salt causes distinct effects on Arabidopsis seedling root xylem, and reveal underlying molecular mechanisms. C_LIO_LISalinity causes intermittent inhibition of protoxylem cell differentiation, generating protoxylem gaps, in Arabidopsis and other eudicot seedlings. The extent of protoxylem gaps positively correlates with salt tolerance. Reduced gibberellin signaling is required for protoxylem gap formation. Mutant analyses reveal that the xylem differentiation regulator VASCULAR RELATED NAC DOMAIN 6 (VND6), along with secondary cell wall-producing and cell wall modifying enzymes, including EXPANSIN A1 (EXP1), are involved in protoxylem gap formation, in a DELLA-dependent manner. C_LIO_LISalt stress impacts seedling survival and formation of protoxylem gaps is a means of enhancing salt tolerance. Salt stress likely reduces levels of bioactive gibberellins, stabilizing DELLAs, which in turn activate multiple factors modifying protoxylem differentiation. Formation of protoxylem gaps is induced in diverse eudicot species suggesting that this is an evolutionary conserved response for salt acclimation in seedlings. C_LI

plant biology↗

bioRxiv2021

The regeneration factors ERF114 and ERF115 act as transducers of mechanical cues to developmental pathways

Plants show an unparalleled regenerative capacity, allowing them to survive severe stress conditions, such as injury, herbivory attack and harsh weather conditions. This potential not only replenishes tissues and restores damaged organs, but can also give rise to whole plant bodies, highlighting the intertwined nature of development and regeneration. It suggests that regeneration and developmental processes respond to the same upstream signals, but how a cell knows which of the two processes to engage is currently unknown. Here, we demonstrate that next to being regulators of regeneration, ETHYENE RESPONSE FACTOR 114 (ERF114) and ERF115 govern developmental growth in the absence of wounding or injury. Increased ERF114 and ERF115 activity is correlated with enhanced xylem maturation and lateral root formation, whereas their knockout results in a decrease in lateral roots and xylem connectivity following grafting. Moreover, we provide evidence that mechanical cues contribute to ERF114 and ERF115 expression in correlation with BZR1 mediated brassinosteroid signaling under both regenerative and developmental conditions. Antagonistically, negative regulation of cell wall extensibility via cell wall-associated mechanosensory FERONIA signaling suppresses their expression under both conditions. Our data suggest a molecular framework in which mechanical perturbations too great to be compensated by adaptive cell wall remodeling results in strong ERF114 and ERF115 expression, switching their role from developmental to regenerative regulators. One-Sentence SummaryMechanical cues drive ERF114/ERF115 expression during lateral root development as well as regeneration.

plant biology↗

bioRxiv2020

Bipartite influence of abscisic acid on xylem differentiation trajectories is dependent on distinct VND transcription factors in Arabidopsis

Plants display a remarkable ability to adjust their growth and development to changes in environmental conditions, such as reduction in water availability. This high degree of plasticity is apparent not only as altered root and shoot growth rates, but also as changes to tissue patterning and cell morphology [1,2]. We have previously shown that Arabidopsis thaliana root xylem displays plastic developmental responses to limited water availability, mediated by non-cell autonomous action of abscisic acid, ABA [2]. Here, we show through analyses of ABA response reporters and tissue specific suppression of ABA signalling that xylem cells act as primary signalling centres for mediation of changes to both xylem cell fate and differentiation rate revealing a cell autonomous control of xylem development by ABA. Transcriptomic changes in response to ABA showed that members of the VASCULAR RELATED NAC DOMAIN (VND) transcription factor family are rapidly activated. Molecular and genetic analyses revealed that the two aspects of xylem developmental changes, cell fate and differentiation rate, are dependent on distinct members of this transcription factor family. Thus, this study provides insights into how different aspects of developmental plasticity can be interlinked, yet genetically independent of each other. Moreover, similarities in phenotypic and molecular responses to ABA in diverse species indicate an evolutionary conservation of the ABA-xylem development regulatory network among eudicots. Hence, this study gives molecular insights on how environmental stress promotes anatomical plasticity to key plant traits with potential relevance for water use optimization and adaptation to drought conditions.

plant biology↗

bioRxiv2017

Pattern-Triggered Immunity And Cell Wall Integrity Maintenance Jointly Modulate Plant Stress Responses

Plant cells are surrounded by walls, which must often meet opposing functional requirements during plant growth and defense. The cells meet them by modifying wall structure and composition in a tightly controlled and adaptive manner. The modifications seem to be mediated by a dedicated cell wall integrity (CWI) maintenance mechanism. Currently the mode of action of the mechanism is not understood and it is unclear how its activity is coordinated with established plant defense signaling. We investigated responses to induced cell wall damage (CWD) impairing CWI and the underlying mechanism in Arabidopsis thaliana. Interestingly inhibitor- and enzyme-derived CWD induced similar, turgor-sensitive stress responses. Genetic analysis showed that the receptor-like kinase (RLK) FEI2 and the mechano-sensitive, plasma membrane-localized Ca2+- channel MCA1 function downstream of the THE1 RLK in CWD perception. Phenotypic clustering with 27 genotypes identified a core group of RLKs and ion channels, required for activation of CWD responses. By contrast, the responses were repressed by pattern-triggered immune (PTI) signaling components including PEPR1 and 2, the receptors for the immune signaling peptide AtPep1. Interestingly AtPep1 application repressed CWD-induced phytohormone accumulation in a PEPR1/2-dependent manner. These results suggest that PTI suppresses CWD-induced defense responses through elicitor peptide-mediated signaling during defense response activation. If PTI is impaired, the suppression of CWD-induced responses is alleviated, thus compensating for defective PTI.\n\nSignificance statementStress resistance and plant growth determine food crop yield and efficiency of bioenergy production from ligno-cellulosic biomass. Plant cell walls are essential elements of the biological processes, therefore functional integrity of the cell walls must be maintained throughout. Here we investigate the plant cell wall integrity maintenance mechanism. We characterize its mode of action, identify essential signaling components and show that the AtPep1 signaling peptide apparently coordinates pattern triggered immunity (PTI) and cell wall integrity maintenance in plants. These results suggest how PTI and cell wall modification coordinately regulate biotic stress responses with plants possibly compensating for PTI impairment through enhanced activation of stress responses regulated by the CWI maintenance mechanism.

plant biology↗