Biology subjects

Ludewig, U.

Publications and source records attributed to Ludewig, U..

5 recordsLinked to original sources

bioRxiv2024

Cytoplasmic calcium influx mediated by Lr14a regulates stomatal immunity against leaf rust in wheat

The race-specific resistance gene Lr14a in wheat confers a unique type of heterogenous resistance reaction. It encodes an ankyrin-repeat transmembrane domain protein that confers immunity against the fungal pathogen Puccinia triticina. Here, we show that Lr14a functions as a calcium-permeable channel, mediating cytoplasmic Ca{superscript 2} influx that is crucial for leaf rust resistance in wheat. Infection with avirulent isolates induced Lr14a expression predominantly in mesophyll cells while triggering cell death in guard cells in wheat. This study revealed a mechanism by which the product of an R gene regulates stomatal immunity non-cell autonomously through the mediation of calcium signaling.

plant biology↗

bioRxiv2021

Moderate DNA methylation changes associated with nitrogen remobilization and leaf senescence in Arabidopsis

O_LIThe lifespan of plants and tissues is restricted by environmental and genetic components. Following the transition to reproductive growth, leaf senescence ceases cellular life in monocarpic plants to remobilize nutrients to storage organs. C_LIO_LIWe observed altered leaf to seed ratios, faster senescence progression and enhanced nitrogen remobilization from the leaves in two methylation mutants (ros1 and the triple dmr1/2 cmt3 knockout). C_LIO_LIDNA methylation in wild type Col-0 leaves initially moderately declined with progressing leaf senescence, predominantly in the CG context, while the ultimate phase of leaf discoloration was associated with moderate de novo methylation of cytosines, primarily in the CHH context. C_LIO_LIRelatively few differentially methylated regions, including one in the ROS1 promoter linked to the down-regulation of ROS1, were present, but these were unrelated to known senescence-associated genes. C_LIO_LIDifferential methylation patterns were identified in transcription factor binding sites, such as the W-boxes that are targeted by WRKYs, which impaired transcription factor binding when methylated in vitro. C_LIO_LIMutants that are defective in DNA methylation showed distinct nitrogen remobilization, which was associated with altered patterns of leaf senescence progression. But moderate methylome changes during leaf senescence were not specifically associated with up-regulated genes during senescence. C_LI

plant biology↗

bioRxiv2021

Abscisic-acid-dependent regulation of Arabidopsis thaliana ammonium transport relies on ABI1 control of CIPK23 and AMT1

Ammonium uptake at plant roots is regulated at the transcriptional, post-transcriptional and post-translational levels. Phosphorylation by the protein kinase CIPK23 transiently inactivates the ammonium transporters (AMT1s) but the phosphatases activating AMT1s remain unknown. Here, we have identified the PP2C phosphatase ABI1 as an activator of AMTs in Arabidopsis thaliana. We show that high external ammonium concentrations elevate the stress phytohormone abscisic acid (ABA) by de-glycosylation. Active ABA is sensed by ABI1-PYL complexes followed by the inactivation of ABI1 activating CIPK23. Under favourable growth conditions, ABI1 reduces AMT1 phosphorylation, both by binding and inactivating CIPK23, and by the direct dephosphorylation of AMT1s. Thus, ABI1 is a positive regulator of ammonium uptake, coupling nutrient acquisition to abiotic stress signalling. Elevated ABA reduces ammonium uptake during stress situations, such as ammonium toxicity, whereas ABI1 reactivates AMT1s under favourable growth conditions.

plant biology↗

bioRxiv2021

Small peptides modulate the immune function of the ion channel-like protein ACD6 in Arabidopsis thaliana

ACCELERATED CELL DEATH 6 (ACD6) mediates a trade-off between growth and defense in Arabidopsis thaliana. However, the precise biochemical mechanism by which ACD6 and related proteins in plants act remains enigmatic. Here, we identified two loci, MODULATOR OF HYPERACTIVE ACD6 1 (MHA1) and its paralog MHA1-LIKE (MHA1L), that code for [~]7 kDa proteins that differentially interact with specific ACD6 variants. MHA1L enhances accumulation of an ACD6 complex, thereby increasing activity of the ACD6 standard allele for regulating plant growth and defenses. ACD6 is a multipass transmembrane protein with intracellular ankyrin repeats that are structurally similar to those found in mammalian ion channels. Several lines of evidence link increased ACD6 activity to enhanced calcium influx, likely mediated by ACD6 itself and with MHA1L as a direct regulator of ACD6.

plant biology↗

bioRxiv2017

Biomass increase under zinc deficiency caused by delay of early flowering in Arabidopsis

Plants generally produce more biomass when all nutrients are available in sufficient amounts. In addition to environmental constraints, genetic and developmental factors, such as the transition from vegetative to reproductive growth, restrict maximal yield. Here we report the peculiar observation that a subset of early flowering Arabidopsis thaliana accessions produced larger shoot rosette diameters when grown in zinc (Zn)-deficient conditions, compared with Zn-sufficient conditions. This was associated with early flowering that restricted the leaf length under Zn sufficiency. Zinc deficiency repressed FLOWERING LOCUS T (FT) expression, a major regulator of flowering. Repression or loss of FT increased the rosette diameter by a delay of the transition to flowering, a longer phase of leaf proliferation and increased leaf number. The transition to flowering reduced, but not terminated, the proliferation of established leaves. The size of individual leaf mesophyll cells was not affected by Zn deficiency or loss of FT, indicating that the larger rosette diameter was caused by maintained proliferation of vegetative tissue. As a consequence, early flowering accessions under Zn deficiency grew larger rosette diameters due to a delay of flowering, which explains the unusual increase of vegetative biomass under nutrient deficiency.\n\nHighlightAn increase in biomass of some Arabidopsis accessions under Zn-deficiency is caused by retardation of flowering, prolonging vegetative growth.\n\nAbbreviations

plant biology↗