Small secreted proteins play an important role in plant development, as well as in reactions to changes in the environment. In Arabidopsis thaliana, they are predominantly members of highly expanded families, such as the pathogenesis-related (PR) 1-like protein family, whose most studied member PR1 is involved in plant defense responses by a so far unknown mechanism, or Clavata3/Endosperm Surrounding Region (CLE) protein family, whose members' functions in the development are well described. Our survey of the existing literature for the two families showed a lack of details on their localization, trafficking, and exocytosis. Therefore, in order to uncover the modes of their secretion, we tested the hypothesis that a direct link between the secreted cargoes and the secretion regulators such as Rab GTPases, SNAREs, and exocyst subunits could be established using in silico co-expression and clustering approaches. We employed several independent techniques to uncover that only weak co-expression links could be found for limited numbers of secreted cargoes and regulators. We propose that there might be particular spatio-temporal requirements for PR1 and CLE proteins to be synthesized and secreted, and efforts to experimentally cover these discrepancies should be invested along with functional studies.

• Klíčová slova
• CLE, PR1, SNARE, co-expression, exocyst, secretion,
• MeSH
• Arabidopsis * genetika   metabolismus   MeSH
• cytoplazma metabolismus   MeSH
• exocytóza fyziologie   MeSH
• proteiny huseníčku * genetika   metabolismus   MeSH
• proteiny SNARE metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• proteiny huseníčku * MeSH
• proteiny SNARE MeSH

Plants can acquire an improved resistance against pathogen attacks by exogenous application of natural or artificial compounds. In a process called chemical priming, application of these compounds causes earlier, faster and/or stronger responses to pathogen attacks. The primed defense may persist over a stress-free time (lag phase) and may be expressed also in plant organs that have not been directly treated with the compound. This review summarizes the current knowledge on the signaling pathways involved in chemical priming of plant defense responses to pathogen attacks. Chemical priming in induced systemic resistance (ISR) and systemic acquired resistance (SAR) is highlighted. The roles of the transcriptional coactivator NONEXPRESSOR OF PR1 (NPR1), a key regulator of plant immunity, induced resistance (IR) and salicylic acid signaling during chemical priming are underlined. Finally, we consider the potential usage of chemical priming to enhance plant resistance to pathogens in agriculture.

• Klíčová slova
• Arabidopsis thaliana, biotic stress, chemical priming, defense priming, induced systemic resistance, pathogen attack, priming, systemic acquired resistance,
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

Natural compounds isolated from macroalgae are promising, ecofriendly, and multifunctional bioinoculants, which have been tested and used in agriculture. Ulvans, for instance, one of the major polysaccharides present in Ulva spp. cell walls, have been tested for their plant growth-promoting properties as well as their ability to activate plant immune defense, on a large variety of crops. Recently, we have characterized for the first time an arabinogalactan protein-like (AGP-like) from Ulva lactuca, which exhibits several features associated to land plant AGPs. In land plant, AGPs were shown to play a role in several plant biological functions, including cell morphogenesis, reproduction, and plant-microbe interactions. Thus, isolated AGP-like proteins may be good candidates for either the plant growth-promoting properties or the activation of plant immune defense. Here, we have isolated an AGP-like enriched fraction from Ulva lactuca and we have evaluated its ability to (i) protect oilseed rape (Brassica napus) cotyledons against Leptosphaeria maculans, and (ii) its ability to activate immune responses. Preventive application of the Ulva AGP-like enriched fraction on oilseed rape, followed by cotyledon inoculation with the fungal hemibiotroph L. maculans, resulted in a major reduction of infection propagation. The noticed reduction correlated with an accumulation of H2O2 in treated cotyledons and with the activation of SA and ET signaling pathways in oilseed rape cotyledons. In parallel, an ulvan was also isolated from Ulva lactuca. Preventive application of ulvan also enhanced plant resistance against L. maculans. Surprisingly, reduction of infection severity was only observed at high concentration of ulvan. Here, no such significant changes in gene expression and H2O2 production were observed. Together, this study indicates that U. lactuca AGP-like glycoproteins exhibit promising elicitor activity and that plant eliciting properties of Ulva extract, might result not only from an ulvan-originated eliciting activities, but also AGP-like originated.

• Klíčová slova
• Arabinogalactan proteins, Ulva lactuca, elicitor, hemibiotrophic fungus, plant defense, plant immunity,
• Publikační typ
• časopisecké články MeSH

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. We found that en route from the endoplasmic reticulum, the PR1 protein transits via the multivesicular body and undergoes partial proteolytic processing, dependent on an intact C-terminal motif. Importantly, only nonmutated or processing-mimicking variants of PR1 are secreted to the apoplast. The C-terminal proteolytic cleavage releases a protein fragment that acts as a modulator of plant defence responses, including localized cell death control. However, other parts of PR1 also have immunity potential unrelated to cell death. The described modes of the PR1 contribution to immunity were found to be tissue-localized and host plant ontogenesis dependent.

• Klíčová slova
• extracellular proteins, multivesicular bodies, pathogenesis-related 1, plant immunity, vesicular trafficking,
• MeSH
• Arabidopsis * metabolismus   MeSH
• endoplazmatické retikulum metabolismus   MeSH
• fyziologický stres MeSH
• imunita rostlin genetika   MeSH
• proteiny huseníčku * metabolismus   MeSH
• regulace genové exprese u rostlin MeSH
• tabák genetika   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• proteiny huseníčku * MeSH

The Arabidopsisthaliana pathogenesis-related 1 (PR1) is an important defense protein, so far it has only been detected in extracellular space and its subcellular sorting and transport remain unexplained. Using a green fluorescent protein (GFP) tagged full length, as well as a C-terminus truncated version of PR1, we observed that when expressed ectopically in Nicotiana benthamiana leaves, PR1 co-localizes only partially with Golgi markers, and much more prominently with the late endosome (LE)/multivesicular body (MVB) FYVE marker. The C-truncated version PR1ΔC predominantly localized to the endoplasmic reticulum (ER). The same localizations were found for stable Arabidopsis transformants with expression of PR1 and PR1ΔC driven by the native promoter. We conclude that the A. thaliana PR1 (AtPR1) undergoes an unconventional secretion pathway, starting from the C-terminus-dependent sorting from the ER, and utilizing further transportation via phosphatidyl-inositol-3-phosphate (PI(3)P) positive LE/MVB-like vesicles. The homology model of the PR1 structure shows that the cluster of positively charged amino acid residues (arginines 60, 67, 137, and lysine 135) could indeed interact with negatively charged phospholipids of cellular membranes. It remains to be resolved whether Golgi and LE/MVB localization reflects an alternative sorting or trafficking succession, and what the role of lipid interactions in it will be.

• Klíčová slova
• CAPE, MVB, PI(3)P, PR1, secretion, trafficking,
• MeSH
• Arabidopsis metabolismus   MeSH
• endoplazmatické retikulum metabolismus   MeSH
• endozomy metabolismus   MeSH
• fosfatidylinositolfosfáty metabolismus   MeSH
• Golgiho aparát metabolismus   MeSH
• konfokální mikroskopie MeSH
• listy rostlin metabolismus   MeSH
• promotorové oblasti (genetika) MeSH
• proteiny huseníčku genetika   metabolismus   MeSH
• rekombinantní fúzní proteiny biosyntéza   genetika   MeSH
• tabák metabolismus   MeSH
• zelené fluorescenční proteiny genetika   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• fosfatidylinositolfosfáty MeSH
• phosphatidylinositol 3-phosphate MeSH Prohlížeč
• PR-1 protein, Arabidopsis MeSH Prohlížeč
• proteiny huseníčku MeSH
• rekombinantní fúzní proteiny MeSH
• zelené fluorescenční proteiny MeSH

Cryptogein is a proteinaceous elicitor secreted by Phytophthora cryptogea that can induce resistance to P. parasitica in tobacco plants. On the basis of previous computer modelling experiments, by site-directed mutagenesis a series of cryptogein variants was prepared with altered abilities to bind sterols, phospholipids or both. The sterol binding and phospholipid transfer activities corresponded well with the previously reported structural data. Induction of the synthesis of reactive oxygen species (ROS) in tobacco cells in suspension and proteomic analysis of intercellular fluid changes in tobacco leaves triggered by these mutant proteins were not proportional to their ability to bind or transfer sterols and phospholipids. However, changes in the intercellular proteome corresponded to transcription levels of defence genes and resistance to P. parasitica and structure-prediction of mutants did not reveal any significant changes in protein structure. These results suggest, contrary to previous proposals, that the sterol-binding ability of cryptogein and its mutants, and the associated conformational change in the ω-loop, might not be principal factors in either ROS production or resistance induction. Nevertheless, the results support the importance of the ω-loop for the interaction of the protein with the high affinity binding site on the plasma membrane.

• MeSH
• fosfolipidy metabolismus   MeSH
• fungální proteiny genetika   metabolismus   MeSH
• imunita rostlin imunologie   MeSH
• kyselina chlorogenová analýza   MeSH
• listy rostlin genetika   imunologie   parazitologie   fyziologie   MeSH
• mutace MeSH
• nemoci rostlin imunologie   parazitologie   MeSH
• Phytophthora genetika   metabolismus   patogenita   MeSH
• proteiny genetika   metabolismus   MeSH
• proteomika metody   MeSH
• reaktivní formy kyslíku metabolismus   MeSH
• rekombinantní proteiny MeSH
• seskviterpeny analýza   MeSH
• steroly metabolismus   MeSH
• tabák genetika   imunologie   parazitologie   fyziologie   MeSH
• vazba proteinů MeSH
• vztahy mezi strukturou a aktivitou MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• capsidiol MeSH Prohlížeč
• cryptogein protein, Phytophthora cryptogea MeSH Prohlížeč
• elicitin, Phytophthora MeSH Prohlížeč
• fosfolipidy MeSH
• fungální proteiny MeSH
• kyselina chlorogenová MeSH
• proteiny MeSH
• reaktivní formy kyslíku MeSH
• rekombinantní proteiny MeSH
• seskviterpeny MeSH
• steroly MeSH