Biology subjects

Vaahtera, L.

Publications and source records attributed to Vaahtera, L..

5 recordsLinked to original sources

bioRxiv2021

THESEUS1 modulates cell wall stiffness and abscisic acid production in Arabidopsis thaliana

Plant cells can be distinguished from animal cells by their cell walls and high turgor pressure. Although changes in turgor and stiffness of cell walls seem coordinated, we know little about the mechanism responsible for coordination. Evidence has accumulated that plants, like yeast, have a dedicated cell wall integrity maintenance mechanism. This mechanism monitors the functional integrity of the wall and maintains it through adaptive responses when cell wall damage occurs during growth, development, and interactions with the environment. The adaptive responses include osmo-sensitive-induction of phytohormone production, defence responses as well as changes in cell wall composition and structure. Here, we investigate how the cell wall integrity maintenance mechanism coordinates changes in cell wall stiffness and turgor in Arabidopsis thaliana. We show that the production of abscisic acid (ABA), the phytohormone modulating turgor pressure and responses to drought, depends on the presence of a functional cell wall. We find that the cell wall integrity sensor THESEUS1 modulates mechanical properties of walls, turgor loss point and ABA biosynthesis. We identify RECEPTOR-LIKE PROTEIN 12 as a new component of cell wall integrity maintenance controlling cell wall damage-induced jasmonic acid production. Based on the results we propose that THE1 is responsible for coordinating changes in turgor pressure and cell wall stiffness. Significance statementPlants need to constantly adapt to a changing environment. This includes responses to biotic and abiotic stress. Key elements influencing the response to abiotic stress are the plant cell walls surrounding all cells and the phytohormone abscisic acid, which influences turgor pressure in plants. Turgor pressure in plant cells is much higher than in animal cells and a key driver of plant growth and development. Here we investigate the mechanism regulating cell wall stiffness and coordinating changes in stiffness and turgor. We characterize key elements of the mechanism and dissect its mode of action. This knowledge will enable us to pursue novel approaches to improve plant resistance to drought stress, which is crucial in a rapidly changing environment.

plant biology↗

bioRxiv2019

Automated Processing and Statistical Analysis of NMR spectra obtained from Arabidopsis thaliana Extracts

To cope with vast amounts of data produced by metabolomic and mixture analysis using NMR, the employed analysis techniques and tools are very important. In this paper, we demonstrate quantitative 1H and 2D-JRES NMR analysis of Arabidopsis thaliana extracts utilizing our ImatraNMR and SimpeleNMR software to automate the processing the spectra, extracting data, and perform statistical analysis of the results. Metabolomes of four different strains of Arabidopsis thaliana are analyzed under control conditions and during acute ozone exposure. Key differences are identified between accessions Col-0 and Cvi-0 (epithionitriles, iberin nitrile) and ozone damage associated metabolite(s) can be identified. Sample stability is also addressed.

biochemistry↗

bioRxiv2019

CRK2-mediated control of ROS production by phosphorylation of the RBOHD C-terminus in Arabidopsis

Reactive oxygen species (ROS) are important messengers in eukaryotic organisms and their production is tightly controlled. Active extracellular ROS production by NADPH oxidases in plants is triggered by receptor-like protein kinase (RLK)-dependent signaling networks. Here we show that the cysteine-rich RLK CRK2 kinase activity is required for plant growth and CRK2 exists in a preformed complex with the NADPH oxidase RBOHD in Arabidopsis. Functional CRK2 is required for the full elicitor-induced ROS burst and consequently the crk2 mutant is impaired in defense against the bacterial pathogen Pseudomonas syringae pv. tomato DC3000. Our work demonstrates that CRK2 regulates plant innate immunity. We identified in vitro CRK2-dependent phosphorylation sites in the C-terminal region of RBOHD. Phosphorylation of S703 RBOHD is enhanced upon flg22 treatment and substitution of S703 with alanine reduced ROS production in Arabidopsis. Phylogenetic analysis suggests that phospho-sites in C-terminal region of RBOHD are conserved throughout the plant lineage and between animals and plants. We propose that regulation of NADPH oxidase activity by phosphorylation of the C-terminal region might be an ancient mechanism and that CRK2 is an important element in regulating MAMP-triggered ROS production. One-sentence summaryCRK2 associates with and activates RBOHD to trigger MAMP-induced ROS production and reveals a novel regulatory mechanism for plant NADPH oxidases through phosphorylation of the C-terminus.

plant biology↗

bioRxiv2019

Functional characterization of genes mediating cell wall metabolism and responses to plant cell wall integrity impairment

Plant cell walls participate in all plant-environment interactions. Maintaining cell wall integrity (CWI) during these interactions is essential. This realization led to increased interest in CWI and resulted in knowledge regarding early perception and signalling mechanisms active during CWI maintenance. By contrast, knowledge regarding processes mediating changes in cell wall metabolism upon CWI impairment is very limited. To identify genes involved and to investigate their contributions to the processes we selected 23 genes with altered expression in response to CWI impairment and characterized the impact of T-DNA insertions in these genes on cell wall composition using Fourier-Transform Infrared Spectroscopy (FTIR) in Arabidopsis thaliana seedlings. Insertions in 14 genes led to cell wall phenotypes detectable by FTIR. A detailed analysis of four genes found that their altered expression upon CWI impairment is dependent on THE1 activity, a key component of CWI maintenance. Phenotypic characterizations of insertion lines suggest that the four genes are required for particular aspects of CWI maintenance, cell wall composition or resistance to Plectosphaerella cucumerina infection in adult plants. Taken together, the results implicate the genes in responses to CWI impairment, cell wall metabolism and/or pathogen defence, thus identifying new molecular components and processes relevant for CWI maintenance.

plant biology↗

bioRxiv2018

Cellulose biosynthesis inhibition reduces cell cycle activity in a nitrate reductase- and cytokinin-dependent manner

O_LIDuring growth, development and defense, cell wall integrity needs to be coordinated with cell cycle activity. In Saccharomyces cerevisiae, coordination is mediated by the cell wall integrity maintenance mechanism. In plants, little is known how coordination is achieved.\nC_LIO_LIHere we investigated coordination between plant cell wall and cell cycle activity in Arabidopsis thaliana seedlings by studying the impact of cell wall damage (CWD, caused by cellulose biosynthesis inhibition) on cell cycle gene expression, growth, phytohormone (jasmonic acid, salicylic acid, cytokinins) and lignin accumulation.\nC_LIO_LIWe found root growth and cell cycle gene expression are reduced by CWD in an osmo-sensitive manner. trans-zeatin application suppressed the CWD effect on gene expression. Quantification of cytokinins revealed CWD-induced, osmo-sensitive changes in several cytokinins. Expression of CYTOKININ OXIDASE2/DEHYDROGENASE (CKX2) and CKX3, encoding cytokinin-degrading enzymes, was elevated in CWD-exposed seedlings. Genetic studies implicated NITRATE REDUCTASE1/2 (NIA1/2) in the response to CWD. In nia1/2 seedlings CWD induced neither expression of CKX2/3 and cell cycle genes nor accumulation of jasmonic acid, salicylic acid and lignin.\nC_LIO_LIThis suggests that CWD causes increased CKX2/3 expression through a NIA1/2-mediated process. Increased CKX expression seems to cause changes in cytokinin levels, leading to reduced cell cycle gene expression.\nC_LI

plant biology↗