Biology subjects

Frigerio, L.

Publications and source records attributed to Frigerio, L..

4 recordsLinked to original sources

bioRxiv2023

Rapid local and systemic jasmonate signalling drives initiation and establishment of plant systemic immunity

Successful recognition of pathogen effectors by plant disease resistance proteins (effector triggered immunity, ETI) contains the invading pathogen through a localized hypersensitive response (HR). In addition, ETI activates long-range signalling cascades that establish broad spectrum systemic acquired resistance (SAR). Using a novel and sensitive reporter we have been able to image the spatio-temporal dynamics of SAR. We demonstrate that local ETI triggered SAR signal generation, followed by rapid propagation and establishment in systemic responding leaves, is dependent on both jasmonate biosynthesis and perception. Further, ETI initiates calcium- and jasmonate-dependent systemic surface electrical potentials, reminiscent of those activated by herbivory but with slower propagation kinetics. Thus, jasmonate signalling is crucial to the initiation and establishment of systemic defence responses against a diverse range of phytopathogens.

plant biology↗

bioRxiv2022

Plant peptidoglycan precursor biosynthesis: Conservation between moss chloroplasts and Gram negative bacteria

An accumulation of evidence suggests that peptidoglycan, consistent with a bacterial cell wall, is synthesised around the chloroplasts of many photosynthetic eukaryotes, from glaucophyte algae to land plants at least as evolved as pteridophyte ferns, but the biosynthetic pathway has not been demonstrated. We employed mass spectrometry and enzymology in a twofold approach to characterize the synthesis of peptidoglycan in chloroplasts of the moss Physcomitrium (Physcomitrella) patens. To drive the accumulation of peptidoglycan pathway intermediates, P.patens was cultured with the antibiotics phosphomycin, D-cycloserine and carbenicillin, which inhibit key peptidoglycan pathway proteins in bacteria. Mass spectrometry of the TCA-extracted moss metabolome revealed elevated levels of five of the predicted intermediates from UDP-GlcNAc through to the UDP-MurNAc-D,L-diaminopimelate (DAP)-pentapeptide. Most Gram negative bacteria, including cyanobacteria, incorporate meso-diaminopimelate (D,L-DAP) into the third residue of the stem peptide of peptidoglycan, as opposed to L-lysine, typical of most Gram positive bacteria. To establish the specificity of D,L-DAP incorporation into the P.patens precursors, we analysed the recombinant protein, UDP-MurNAc-tripeptide ligase (MurE), from both P.patens and the cyanobacterium Anabaena sp. strain PCC 7120. Both ligases incorporated D,L-DAP in almost complete preference to L-Lys, consistent with the mass spectrophotometric data, with catalytic efficiencies similar to previously documented Gram negative bacterial MurE ligases. We discuss how these data accord with the conservation of active site residues common to DL-DAP-incorporating bacterial MurE ligases and of the probability of a horizontal gene transfer event within the plant peptidoglycan pathway.

evolutionary biology↗

bioRxiv2020

The plant endoplasmic reticulum is both receptive and responsive to pathogen effectors

The endoplasmic reticulum (ER) is the entry point to the secretory pathway and, as such, is critical for adaptive responses to biotic stress, when the demand for de novo synthesis of immunity-related proteins and signalling components increases significantly. Comprised of a network of interconnected tubules and cisternae, the architecture of the ER is highly pleomorphic and dynamic, rapidly remodelling to meet new cellular requirements. During infection with the hemi-biotrophic phytopathogen, Pseudomonas syringae pv. tomato DC3000, the ER in cells immediately adjacent to established bacterial colonies condenses into knot-like structures, reminiscent of fenestrated sheets. Based on known temporal dynamics of pathogen effector delivery and initial bacterial multiplication, the timing of these observed morphological changes is rapid and independent of classical elicitor activation of pathogen-triggered immunity. To further investigate a role for ER reconfiguration in suppression of plant immunity we identified a conserved C-terminal tail-anchor domain in a set of pathogen effectors known to localize to the ER and used this protein topology in an in silico screen to identify putative ER-localised effectors within the effectorome of the oomycete Phytophthora infestans. Subsequent characterization of a subset of 15 candidate tail-anchored P. infestans effectors revealed that 11 localised to the ER and/or Golgi. Notably, transient expression of an ER-localised effector from the closely related oomycete, Plasmopara halstedii, reconfigured the ER network, revealing intimate association of labelled ER with perinuclear chloroplasts and clusters of chloroplasts, potentially facilitating retrograde signalling during plant defence.

plant biology↗

bioRxiv2018

Arabidopsis Lunapark proteins are involved in ER cisternae formation

The plant endoplasmic reticulum (ER) is crucial to the maintenance of cellular homeostasis. The ER consists of a dynamic and continuously remodelling network of tubules and cisternae. Several conserved membrane proteins have been implicated in formation and maintenance of the ER network in plants, such as RHD3 and the reticulon family of proteins.\n\nDespite the recent work in mammalian and yeast cells, the detailed molecular mechanisms of ER network organisation in plants still remain largely unknown. Recently novel ER network-shaping proteins called Lunapark have been identified in yeast and mammalian cells.\n\nHere we identify two arabidopsis LNP homologues and investigate their subcellular localisation via confocal microscopy and potential function in shaping the ER network using protein-protein interaction assays and mutant analysis.\n\nWe show that AtLNP1 overexpression in tobacco leaf epidermal cells mainly labels the three-way junctions (trivia) of the ER network whereas AtLNP2 labels the whole ER. Overexpression of LNP proteins results in an increased abundance of ER cisternae and an lnp1lnp2 amiRNA line displays a less structured ER network.\n\nThus, we hypothesize that AtLNP1 and AtLNP2 are involved in determining the dynamic morphology of the plant ER, possibly by regulating the formation of ER cisternae.

plant biology↗