scholarly journals Flagellin triggers mesophyll dehydration: An early PTI defense against bacterial establishment in intercellular spaces

2021 ◽  
Author(s):  
Ahan Dalal ◽  
Ziv Attia ◽  
Menachem Moshelion
Keyword(s):  
Cell Wall ◽  
Signal Transduction Pathway ◽  
Effector Proteins ◽  
Cell Membrane Permeability ◽  
Transduction Pathway ◽  
Intercellular Spaces ◽  
Atmospheric Humidity ◽  
Mesophyll Cells ◽  
Osmotic Water ◽  
Bundle Sheath Cells

Plants have evolved various mechanisms to defend themselves against pathogens. Many pathogens induce the formation of water-soaked lesions during early infection under conditions of high atmospheric humidity. These water-soaked spots are caused by the disruption of the plasma membrane or cell wall integrity due to various activities of effector proteins during infection. We hypothesized that bacterial PAMP-flagellin plays a role in modulating the cell-membrane permeability that controls the availability of water in the apoplast, to prevent bacterial establishment on the cell wall during the early stages of the PAMP-triggered immunity (PTI) response. Our results revealed that the conductivity of hydraulic pathways in the leaf was reduced in response to flagellin22 (flg22). The cellular osmotic water permeability (Pf) of both mesophyll cells and bundle-sheath cells was dramatically reduced in response to flg22 treatment. Moreover, the whole-leaf hydraulic conductance (Kleaf) was also reduced in response to flg22 treatment. The fact that the Pf of mesophyll cells of an aquaporin (AQP) mutant was not affected by the flg22 treatment suggests the involvement of AQP channels in the flg22-induced Pf reduction signal transduction pathway. We conclude that the binding of flagellin to their receptors elicits signals to close AQPs, consequently reducing the water content of the cell wall and intercellular spaces and leading to a more negative water potential. This serves as an early PTI response to pathogen attack, which, in turn, might decrease the rate of bacterial growth and establishment in the apoplast.

scholarly journals Different Cell Wall-Degradation Ability Leads to Tissue-Specificity between Xanthomonas oryzae pv. oryzae and Xanthomonas oryzae pv. oryzicola

Pathogens ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 187
Author(s):  
Jianbo Cao ◽  
Chuanliang Chu ◽  
Meng Zhang ◽  
Limin He ◽  
Lihong Qin ◽  
...  
Keyword(s):  
Cell Wall ◽  
Tissue Specificity ◽  
Mesophyll Cell ◽  
Xanthomonas Oryzae ◽  
Cell Wall Degradation ◽  
Intercellular Spaces ◽  
Mesophyll Cells ◽  
Degradation Ability

Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas oryzae pv. oryzicola (Xoc) lead to the devastating rice bacterial diseases and have a very close genetic relationship. There are tissue-specificity differences between Xoo and Xoc, i.e., Xoo only proliferating in xylem vessels and Xoc spreading in intercellular space of mesophyll cell. But there is little known about the determinants of tissue-specificity between Xoo and Xoc. Here we show that Xoc can spread in the intercellular spaces of mesophyll cells to form streak lesions. But Xoo is restricted to growth in the intercellular spaces of mesophyll cells on the inoculation sites. In vivo, Xoc largely breaks the surface and inner structures of cell wall in mesophyll cells in comparison with Xoo. In vitro, Xoc strongly damages the cellulose filter paper in comparison with Xoo. These results suggest that the stronger cell wall-degradation ability of Xoc than that of Xoo may be directly determining the tissue-specificity.

Intercellular pectic protuberances in leaves of some Xyris species (Xyridaceae)

1996 ◽  
Vol 74 (9) ◽  
pp. 1539-1541 ◽  
Author(s):  
S.R. Machado ◽  
M. G. Sajo
Keyword(s):  
Cell Wall ◽  
Species Level ◽  
Intercellular Spaces ◽  
Mesophyll Cells ◽  
Transmission Microscopy ◽  
Standard Methods ◽  
Electron Transmission ◽  
Mature Leaves ◽  
Periclinal Walls ◽  
Electron Transmission Microscopy

Mature leaves of eight species of Xyris were prepared by standard methods for electron transmission microscopy. Wartlike intercellular pectic protuberances were observed on the surface of inner periclinal walls of epidermal cells in Xyris obcordata, Xyris hymenachne, and Xyris pterygoblephara. In the latter, the protuberances also occur on the surface of parenchymatic mesophyll cells; they frequently project into intercellular spaces and may connect opposing cells. For the genus Xyris, the intercellular pectic protuberances may be considered taxonomically significant at the species level. Keywords: Xyris, Xyridaceae, pectin, cell wall.

Intercellular pectic strands in parenchyma: studies of plant cell walls by scanning electron microscopy.

1975 ◽  
Vol 23 (1) ◽  
pp. 95 ◽  
Author(s):  
SGM Carr ◽  
DJ Carr
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Cell Wall ◽  
Chemical Composition ◽  
Light Microscope ◽  
Cell Walls ◽  
Plant Cell Walls ◽  
Intercellular Spaces ◽  
Mesophyll Cells ◽  
Scanning Electron

Rows of pectic strands, each 0.3-0.4�m in diameter, are shown to connect palisade mesophyll cells in regular ladder-like configurations ('pectic scala'). These structures are illustrated in some species of eucalypts, but probably occur in other kinds of plants. Less regular wall filaments can be observed in the intercellular spaces between other types of cells. They are particularly numerous in the parenchyma of species of ferns. These filaments and the pectic scala are readily observable by scanning electron microscopy, but can also be seen in conventional preparations for the light microscope. The structure, formation, chemical composition and possible function of these and other kinds of cell wall protuberances, described in the literature, are discussed.

scholarly journals New Insights into the WalK/WalR (YycG/YycF) Essential Signal Transduction Pathway Reveal a Major Role in Controlling Cell Wall Metabolism and Biofilm Formation in Staphylococcus aureus

2007 ◽  
Vol 189 (22) ◽  
pp. 8257-8269 ◽  
Author(s):  
Sarah Dubrac ◽  
Ivo Gomperts Boneca ◽  
Olivier Poupel ◽  
Tarek Msadek
Keyword(s):  
Signal Transduction ◽  
Staphylococcus Aureus ◽  
Cell Wall ◽  
Biofilm Formation ◽  
Signal Transduction Pathway ◽  
Physiological Role ◽  
Regulatory System ◽  
Wall Structure ◽  
Transduction Pathway ◽  
Cell Wall Metabolism

ABSTRACT The highly conserved WalK/WalR (also known as YycG/YycF) two-component system is specific to low-G+C gram-positive bacteria. While this system is essential for cell viability, both the nature of its regulon and its physiological role have remained mostly uncharacterized. We observed that, unexpectedly, Staphylococcus aureus cell death induced by WalKR depletion was not followed by lysis. We show that WalKR positively controls autolytic activity, in particular that of the two major S. aureus autolysins, AtlA and LytM. By using our previously characterized consensus WalR binding site and carefully reexamining the genome annotations, we identified nine genes potentially belonging to the WalKR regulon that appeared to be involved in S. aureus cell wall degradation. Expression of all of these genes was positively controlled by WalKR levels in the cell, leading to high resistance to Triton X-100-induced lysis when the cells were starved for WalKR. Cells lacking WalKR were also more resistant to lysostaphin-induced lysis, suggesting modifications in cell wall structure. Indeed, lowered levels of WalKR led to a significant decrease in peptidoglycan biosynthesis and turnover and to cell wall modifications, which included increased peptidoglycan cross-linking and glycan chain length. We also demonstrated a direct relationship between WalKR levels and the ability to form biofilms. This is the first example in S. aureus of a regulatory system positively controlling autolysin synthesis and biofilm formation. Taken together, our results now define this signal transduction pathway as a master regulatory system for cell wall metabolism, which we have accordingly renamed WalK/WalR to reflect its true function.

Ultrastructure and Senescence in an Achloroplastic Mutant of Hordeum vulgare L. cv. Dyan

1992 ◽  
Vol 50 (1) ◽  
pp. 844-845
Author(s):  
R.H.M. Cross ◽  
C.E.J. Botha ◽  
A.K. Cowan ◽  
B.J. Hartley
Keyword(s):  
Cell Wall ◽  
Hordeum Vulgare ◽  
Leaf Tissue ◽  
Ultrastructural Changes ◽  
Hordeum Vulgare L ◽  
Mesophyll Cells ◽  
Lethal Mutant ◽  
Cytoplasmic Matrix ◽  
Close Proximity ◽  
Pinocytotic Vesicles

Senescence is an ordered degenerative process leading to death of individual cells, organs and organisms. The detection of a conditional lethal mutant (achloroplastic) of Hordeum vulgare has enabled us to investigate ultrastructural changes occurring in leaf tissue during foliar senescence.Examination of the tonoplast structure in six and 14 day-old mutant tissue revealed a progressive degeneration and disappearance of the membrane, apparently starting by day six in the vicinity of the mitochondria associated with the degenerating proplastid (Fig. 1.) where neither of the plastid membrane leaflets is evident (arrows, Fig. 1.). At this stage there was evidence that the mitochondrial membranes were undergoing retrogressive changes, coupled with disorganization of cristae (Fig. 2.). Proplastids (P) lack definitive prolamellar bodies. The cytoplasmic matrix is largely agranular, with few endoplasmic reticulum (ER) cisternae or polyribosomal aggregates. Interestingly, large numbers of actively-budding dictysomes, associated with pinocytotic vesicles, were observed in close proximity to the plasmalemma of mesophyll cells (Fig. 3.). By day 14 however, mesophyll cells showed almost complete breakdown of subcellular organelle structure (Fig. 4.), and further evidence for the breakdown of the tonoplast. The final stage of senescence is characterized by the solubilization of the cell wall due to expression and activity of polygalacturonase and/or cellulose. The presence of dictyosomes with associated pinocytotic vesicles formed from the mature face, in close proximity to both the plasmalemma and the cell wall, would appear to support the model proposed by Christopherson for the secretion of cellulase. This pathway of synthesis is typical for secretory glycoproteins.

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