Chitosan stimulates root hair callose deposition, endomembrane dynamics, and inhibits root hair growth.

Although angiosperm plants generally react to immunity elicitors like chitin or chitosan by the cell wall callose deposition, this response in particular cell types, especially upon chitosan treatment, is not fully understood. Here we show that the growing root hairs (RHs) of Arabidopsis can respond to a mild (0.001%) chitosan treatment by the callose deposition and by a deceleration of the RH growth.

Silurian Climatic Zonation of Cryptospore, Trilete Spore and Plant Megafossils, with Emphasis on the Přídolí Epoch.

This paper describes dispersed cryptospores and trilete spores from tropical, temperate and cool climate belts within Přídolí and compares them with the land plant megafossil record. The palynology of earlier intervals in the Silurian are also reviewed. A common feature of the cryptospore and trilete spore records is that their number is surprisingly lowest in the tropical climatic belt and much higher in the temperate and especially in the cool latitude, and the highest number of cryptospore taxa occurring only in one belt is found in the cool belt while the highest number of trilete spore taxa that occurred only in one belt is recorded in the temperate belt.

Interplay of EXO70 and MLO proteins modulates trichome cell wall composition and susceptibility to powdery mildew.

Exocyst component of 70-kDa (EXO70) proteins are constituents of the exocyst complex implicated in vesicle tethering during exocytosis. MILDEW RESISTANCE LOCUS O (MLO) proteins are plant-specific calcium channels and some MLO isoforms enable fungal powdery mildew pathogenesis. We here detected an unexpected phenotypic overlap of Arabidopsis thaliana exo70H4 and mlo2 mlo6 mlo12 triple mutant plants regarding the biogenesis of leaf trichome secondary cell walls.

Exocyst functions in plants: secretion and autophagy.

Tethering complexes mediate vesicle-target compartment contact. Octameric complex exocyst initiate vesicle exocytosis at specific cytoplasmic membrane domains. Plant exocyst is possibly stabilized at the membrane by a direct interaction between SEC3 and EXO70A.

Diversification of SEC15a and SEC15b isoforms of an exocyst subunit in seed plants is manifested in their specific roles in Arabidopsis sporophyte and male gametophyte.

The exocyst complex is an octameric evolutionarily conserved tethering complex engaged in the regulation of polarized secretion in eukaryotic cells. Here, we focus on the systematic comparison of two isoforms of the SEC15 exocyst subunit, SEC15a and SEC15b. We infer that SEC15 gene duplication and diversification occurred in the common ancestor of seed plants (Spermatophytes).

Cryogenian Glacial Habitats as a Plant Terrestrialisation Cradle - The Origin of the Anydrophytes and Zygnematophyceae Split.

For tens of millions of years (Ma), the terrestrial habitats of Snowball Earth during the Cryogenian period (between 720 and 635 Ma before present-Neoproterozoic Era) were possibly dominated by global snow and ice cover up to the equatorial sublimative desert. The most recent time-calibrated phylogenies calibrated not only on plants but on a comprehensive set of eukaryotes indicate that within the Streptophyta, multicellular charophytes (Phragmoplastophyta) evolved in the Mesoproterozoic to the early Neoproterozoic. At the same time, Cryogenian is the time of the likely origin of the common ancestor of Zygnematophyceae and Embryophyta and later, also of the Zygnematophyceae-Embryophyta split.

Immunity functions of Arabidopsis pathogenesis-related 1 are coupled but not confined to its C-terminus processing and trafficking.

The pathogenesis-related 1 (PR1) proteins are members of the cross-kingdom conserved CAP superfamily (from Cysteine-rich secretory protein, Antigen 5, and PR1 proteins). PR1 mRNA expression is frequently used for biotic stress monitoring in plants; however, the molecular mechanisms of its cellular processing, localization, and function are still unknown. To analyse the localization and immunity features of Arabidopsis thaliana PR1, we employed transient expression in Nicotiana benthamiana of the tagged full-length PR1 construct, and also disrupted variants with C-terminal truncations or mutations.

Arabidopsis EXO70B2 exocyst subunit contributes to papillae and encasement formation in antifungal defence.

In the reaction to non-adapted Blumeria graminis f. sp. hordei (Bgh), Arabidopsis thaliana leaf epidermal cells deposit cell wall reinforcements called papillae or seal fungal haustoria in encasements, both of which involve intensive exocytosis.

Dynamics of Silurian Plants as Response to Climate Changes.

The most ancient macroscopic plants fossils are Early Silurian cooksonioid sporophytes from the volcanic islands of the peri-Gondwanan palaeoregion (the Barrandian area, Prague Basin, Czech Republic). However, available palynological, phylogenetic and geological evidence indicates that the history of plant terrestrialization is much longer and it is recently accepted that land floras, producing different types of spores, already were established in the Ordovician Period. Here we attempt to correlate Silurian floral development with environmental dynamics based on our data from the Prague Basin, but also to compile known data on a global scale.

Plasma membrane phospholipid signature recruits the plant exocyst complex via the EXO70A1 subunit.

Polarized exocytosis is essential for many vital processes in eukaryotic cells, where secretory vesicles are targeted to distinct plasma membrane domains characterized by their specific lipid-protein composition. Heterooctameric protein complex exocyst facilitates the vesicle tethering to a target membrane and is a principal cell polarity regulator in eukaryotes. The architecture and molecular details of plant exocyst and its membrane recruitment have remained elusive.

Functional Specialization within the EXO70 Gene Family in Arabidopsis.

Localized delivery of plasma-membrane and cell-wall components is a crucial process for plant cell growth. One of the regulators of secretory-vesicle targeting is the exocyst tethering complex. The exocyst mediates first interaction between transport vesicles and the target membrane before their fusion is performed by SNARE proteins.

SEC6 exocyst subunit contributes to multiple steps of growth and development of Physcomitrella (Physcomitrium patens).

Spatially directed cell division and expansion is important for plant growth and morphogenesis and relies on cooperation between the cytoskeleton and the secretory pathway. The phylogenetically conserved octameric complex exocyst mediates exocytotic vesicle tethering at the plasma membrane. Unlike other exocyst subunits of land plants, the core exocyst subunit SEC6 exists as a single paralog in Physcomitrium patens and Arabidopsis thaliana genomes.

Regulation of Exocyst Function in Pollen Tube Growth by Phosphorylation of Exocyst Subunit EXO70C2.

Exocyst is a heterooctameric protein complex crucial for the tethering of secretory vesicles to the plasma membrane during exocytosis. Compared to other eukaryotes, exocyst subunit EXO70 is represented by many isoforms in land plants whose cell biological and biological roles, as well as modes of regulation remain largely unknown. Here, we present data on the phospho-regulation of exocyst isoform EXO70C2, which we previously identified as a putative negative regulator of exocyst function in pollen tube growth.

EXO70A2 Is Critical for Exocyst Complex Function in Pollen Development.

Pollen development, pollen grain germination, and pollen tube elongation are crucial biological processes in angiosperm plants that need precise regulation to deliver sperm cells to ovules for fertilization. Highly polarized secretion at a growing pollen tube tip requires the exocyst tethering complex responsible for specific targeting of secretory vesicles to the plasma membrane. Here, we demonstrate that Arabidopsis () EXO70A2 (At5g52340) is the main exocyst EXO70 isoform in the male gametophyte, governing the conventional secretory function of the exocyst, analogous to EXO70A1 (At5g03540) in the sporophyte.

Synergy among Exocyst and SNARE Interactions Identifies a Functional Hierarchy in Secretion during Vegetative Growth.

Vesicle exocytosis underpins signaling and development in plants and is vital for cell expansion. Vesicle tethering and fusion are thought to occur sequentially, with tethering mediated by the exocyst and fusion driven by assembly of soluble NSF attachment protein receptor (SNARE) proteins from the vesicle membrane (R-SNAREs or vesicle-associated membrane proteins [VAMPs]) and the target membrane (Q-SNAREs). Interactions between exocyst and SNARE protein complexes are known, but their functional consequences remain largely unexplored.

Redundant and Diversified Roles Among Selected EXO70 Paralogs During Biotic Stress Responses.

The heterooctameric vesicle-tethering complex exocyst is important for plant development, growth, and immunity. Multiple paralogs exist for most subunits of this complex; especially the membrane-interacting subunit EXO70 underwent extensive amplification in land plants, suggesting functional specialization. Despite this specialization, most Arabidopsis mutants are viable and free of developmental defects, probably as a consequence of redundancy among isoforms.

Division of Labor Between Two Actin Nucleators-the Formin FH1 and the ARP2/3 Complex-in Epidermal Cell Morphogenesis.

The ARP2/3 complex and formins are the only known plant actin nucleators. Besides their actin-related functions, both systems also modulate microtubule organization and dynamics. Loss of the main housekeeping Class I membrane-targeted formin FH1 (At3g25500) is known to increase cotyledon pavement cell lobing, while mutations affecting ARP2/3 subunits exhibit an opposite effect.

Functional analysis of phospholipase Dδ family in tobacco pollen tubes.

Phosphatidic acid (PA), an important signalling and metabolic phospholipid, is predominantly localized in the subapical plasma membrane (PM) of growing pollen tubes. PA can be produced from structural phospholipids by phospholipase D (PLD), but the isoforms responsible for production of PM PA were not identified yet and their functional roles remain unknown. Following genome-wide bioinformatic analysis of the PLD family in tobacco, we focused on the pollen-overrepresented PLDδ class.

Protein Prenylation in Plant Stress Responses.

Protein prenylation is one of the most important posttranslational modifications of proteins. Prenylated proteins play important roles in different developmental processes as well as stress responses in plants as the addition of hydrophobic prenyl chains (mostly farnesyl or geranyl) allow otherwise hydrophilic proteins to operate as peripheral lipid membrane proteins. This review focuses on selected aspects connecting protein prenylation with plant responses to both abiotic and biotic stresses.

Three subfamilies of exocyst EXO70 family subunits in land plants: early divergence and ongoing functional specialization.

Localized delivery of plasma membrane and cell wall components is an essential process in all plant cells. The vesicle-tethering complex, the exocyst, an ancient eukaryotic hetero-octameric protein cellular module, assists in targeted delivery of exocytosis vesicles to specific plasma membrane domains. Analyses of Arabidopsis and later other land plant genomes led to the surprising prediction of multiple putative EXO70 exocyst subunit paralogues.