Biology subjects

Thiele, B.

Publications and source records attributed to Thiele, B..

3 recordsLinked to original sources

bioRxiv2021

Tomato leaves under stress: A comparison of stress response to mild abiotic stress between a cultivated and a wild tomato species

Tomato is one of the most produced crop plants on earth and growing in the fields and greenhouses all over the world. Breeding with known traits of wild species can enhance stress tolerance of cultivated crops. In this study, we investigated responses of the transcriptome as well as primary and secondary metabolites in leaves of a cultivated and a wild tomato to several abiotic stresses such as nitrogen deficiency, chilling or warmer temperatures, elevated light intensities and combinations thereof. The wild species responded different to varied temperature conditions compared to the cultivated tomato. Nitrogen deficiency caused the strongest responses and induced in particular the secondary metabolism in both species but to much higher extent in the cultivated tomato. Our study supports the potential of a targeted induction of valuable secondary metabolites in green residues of horticultural production, that will otherwise only be composted after fruit harvest. In particular, the cultivated tomato showed a strong induction in the group of mono caffeoylquinic acids in response to nitrogen deficiency. In addition, the observed differences in stress responses between cultivated and wild tomato can lead to new breeding targets for better stress tolerance.

plant biology↗

bioRxiv2021

Evidence for a bacterial Lands cycle phospholipase A: Structural and mechanistic insights into membrane phospholipid remodeling

Cells steadily adapt their membrane glycerophospholipid (GPL) composition to changing environmental and developmental conditions. While the regulation of membrane homeostasis via GPL synthesis in bacteria has been studied in detail, the mechanisms underlying the controlled degradation of endogenous GPLs remain unknown. Thus far, the function of intracellular phospholipases A (PLAs) in GPL remodeling (Lands cycle) in bacteria is not clearly established. Here, we identified the first cytoplasmic membrane-bound phospholipase A1 (PlaF) from Pseudomonas aeruginosa involved in the Lands cycle. PlaF is an important virulence factor, as the P. aeruginosa {Delta}plaF mutant showed strongly attenuated virulence in Galleria mellonella and macrophages. We present a 2.0-[A]-resolution crystal structure of PlaF, the first structure that reveals homodimerization of a single-pass transmembrane (TM) full-length protein. PlaF dimerization, mediated solely through the intermolecular interactions of TM and juxtamembrane regions, inhibits its activity. A dimerization site and the catalytic sites are linked by an intricate ligand-mediated interaction network which likely explains the product (fatty acid) feedback inhibition observed with the purified PlaF protein. We used molecular dynamics simulations and configurational free energy computations to suggest a model of PlaF activation through a coupled monomerization and tilting of the monomer in the membrane, which constrains the active site cavity into contact with the GPL substrates. Thus, these data show the importance of the GPL remodeling pathway for virulence and pave the way for the development of a novel therapeutic class of antibiotics targeting PlaF-mediated membrane GPL remodeling. SynopsisMembrane homeostasis can be regulated by phospholipase-controlled deacylation of endogenous glycerophospholipids (GPLs) followed by reacylation of products, known as the Lands cycle in eukaryotes. Here we show that the human pathogen Pseudomonas aeruginosa uses intracellular phospholipase A1 (PlaF) to modulate membrane GPL composition, which is the first example in bacteria. This newly identified PLA1 indirectly regulates the bacterial virulence properties by hydrolyzing a specific set of membrane GPLs. The crystal structure of full-length PlaF dimers bound to natural ligands, MD simulations, and biochemical approaches provide insights into the molecular mechanism of dimerization-mediated inactivation of this single-pass transmembrane PLA1. Our findings shed light on a mechanism by which bacterial intracellular PLAs might regulate membrane homeostasis what showcases these enzymes as a promising target for a new class of antibiotics.

molecular biology↗

bioRxiv2021

Novel intracellular phospholipase B from Pseudomonas aeruginosa with activity towards endogenous phospholipids affects biofilm assembly

Pseudomonas aeruginosa is a severe threat to immunocompromised patients due to its numerous virulence factors and multiresistance against antibiotics. This bacterium produces and secretes various toxins with hydrolytic activities including phospholipases A, C and D. However, the function of intracellular phospholipases for bacterial virulence has still not been established. Here we demonstrate that the hypothetical gene pa2927 of P. aeruginosa encodes a novel phospholipase B named PaPlaB. PaPlaB isolated from detergent-solubilized membranes of E. coli rapidly degraded various GPLs including endogenous GPLs isolated from P. aeruginosa cells. Cellular localization studies suggest that PaPlaB is peripherally bound to the inner and outer membrane of E. coli, yet the active form was predominantly associated with the cytoplasmic membrane. In vitro activity of purified and detergent-stabilized PaPlaB increases at lower protein concentrations. The size distribution profile of PaPlaB oligomers revealed that decreasing protein concentration triggers oligomer dissociation. These results indicate that homooligomerisation regulates PaPlaB activity by a yet unknown mechanism, which might be required for preventing bacteria from self-disrupting the membrane. We demonstrated that PaPlaB is an important determinant of the biofilm lifestyle of P. aeruginosa, as shown by biofilm quantification assay and confocal laser scanning microscopic analysis of biofilm architecture. This novel intracellular phospholipase B with a putative virulence role contributes to our understanding of membrane GPL degrading enzymes and may provide a target for new therapeutics against P. aeruginosa biofilms.

biochemistry↗