Downstream Targets of Cyclic Nucleotides in Plants

Efficient integration of various external and internal signals is required to maintain adaptive cellular function. Numerous distinct signal transduction systems have evolved to allow cells to receive these inputs, to translate their codes and, subsequently, to expand and integrate their meanings. Two of these, cyclic AMP and cyclic GMP, together referred to as the cyclic nucleotide signaling system, are between them. The cyclic nucleotides regulate a vast number of processes in almost all living organisms. Once synthesized by adenylyl or guanylyl cyclases, cyclic nucleotides transduce signals by acting through a number of cellular effectors. Because the activities of several of these effectors are altered simultaneously in response to temporal changes in cyclic nucleotide levels, agents that increase cAMP/cGMP levels can trigger multiple signaling events that markedly affect numerous cellular functions. In this mini review, we summarize recent evidence supporting the existence of cNMP effectors in plant cells. Specifically, we highlight cAMP-dependent protein kinase A (PKA), cGMP-dependent kinase G (PKG), and cyclic nucleotide phosphodiesterases (PDEs). Essentially this manuscript documents the progress that has been achieved in recent decades in improving our understanding of the regulation and function of cNMPs in plants and emphasizes the current gaps and unanswered questions in this field of plant signaling research

Interactive physiological response of potato (Solanum tuberosum L.) plants to fungal colonization and Potato virus Y (PVY) infection

Potato plants can be colonized by various viruses and by symbiotic, saprophytic and pathogenic fungi. However, the significance of interactions of viral infection and fungal colonization is hardly known. This work presents a model experiment in which the influence of three different types of fungal associations on the growth and physiology of the potato variety Pirol was tested individually or in combination with infection by PVY. It was hypothesized that simultaneous viral and fungal infections increase the biotic stress of the host plant, but mutualistic plant-fungal associations can mask the impact of viral infection. In the present study, a symbiotic arbsucular mycorrhizal fungus, Glomus intraradices, significantly stimulated the growth of plants infected with PVY. In contrast, two saprophytic Trichoderma spp. strains either did not influence or even inhibited the growth of PVY-infected plants. Also, inoculation of PVY-infected potato plants with a pathogenic strain of Colletotrichum coccodes did not inhibit the plant growth. Growth of the PVY-free potato plants was not promoted by the symbiotic fungus, whereas T. viride, T. harzianum and C. coccodes had an evident inhibitory effect. The strongest growth inhibition and highest concentration of H2O2, as an indicator of biotic stress, was observed in PVY-free potato plants inoculated with T. harzianum and C. coccodes strains. Surprisingly, ultrastructural analysis of PVY-infected plant roots colonized by G. intraradices showed virus-like structures in the arbuscules. This pointed to the possibility of mycorrhizal-mediated transmission of virus particles and has to be further examined by testing with immunoassays and real transmission to uninfected plants. In conclusion, although mycorrhiza formation might decrease the impact of PVY infection on plants, a possible role of mycorrhizal fungi as virus vectors is discussed

The level of phyA in Pharbitis nil Chois during the photoperiodic flower induction

The aim of this work was to determine if there is any relationship between an endogenous phyA level and photoperiodic flower induction. The level of phyA was characterised with polyclonal antibodies directed to phyA from pea. At first it was detected that phyA level is predominant in cotyledons, whereas in roots and stems the concentration of labile phytochrome is rather low. So cotyledons were used for later experiments. In these cotyledons exposed to light illumination a rapid destruction of phyA has been observed. The loss of extractable phyA chromoprotein occurs already after 60 min of irradiation. Pharbitis nil is a short-day plant and a single 16-hours-long dark period is fully inductive. We assessed that phyA level is extremely low during a long inductive night and an immunodetectable phytochrome appears only after 24 hours of darkness. The obtained results suggest that labile phytochrome is not taking part in the direct control of the photoperiodic flower induction

Plant effectors of cyclic nucleotides

Mechanizmy, za pomocą których sygnały wewnątrz- i zewnątrzkomórkowe wywołują specyficzną odpowiedź biologiczną są istotne dla regulacji funkcji komórek, procesów wzrostu i rozwoju oraz odpowiedzi na zmiany środowiska. W ostatnich latach dokonał się ogromny postęp w badaniu elementów zaangażowanych w regulację procesów zachodzących w komórkach roślinnych o czym świadczy olbrzymia ilość publikacji poruszających problem sygnalizacji komórkowej. Cykliczne nukleotydy (cNMP) są cząsteczkami sygnalnymi, których obecność i zaangażowanie w szereg procesów w komórkach roślinnych nie budzą już wątpliwości. Z fizjologicznego punktu widzenia, stężenie cNMP w miejscu ich działania nie może być ani za wysokie ani za niskie, a jest to normowane przez odpowiednie układy generujące i inaktywujące cykliczne nukleotydy. Ponadto na końcowy efekt biologiczny ma wpływ sprawność systemów efektorowych wrażliwych na zmiany stężenia cyklicznych nukleotydów takich jak fosfodiesterazy, kinazy regulowane lub zależne od cNMP i kanały bramkowane cyklicznymi nukleotydami. W pracy tej podsumowano aktualną wiedzę dotyczącą efektorów cyklicznych nukleotydów, skupiając się zarówno na ich budowie, jak i aspekcie ich funkcjonowania w komórkach roślinnych.The mechanisms by which intra- and extracellular signals induce a specific biological response are important for the regulation of cell function, processes of growth and development and responses to environmental changes. In recent years, enormous progress has been made in studies of elements involved in the regulation of processes occurring in plant cells. Cyclic nucleotides (cNMP) are signaling molecules whose presence and involvement in a number of processes in plant cells is well documented. From the physiological point of view, the concentration of cNMP's at a site of their action could be neither too high nor too low, as it is controlled by the systems that lead to their synthesis or inactivation. In addition, the final biological effect depends on the efficiency of the effector systems such as cyclic nucleotide phosphodiesterases, cNMP-dependent or cNMP-regulated protein kinase and cyclic-nucleotide gated channels, that are sensitive to changes in cNMP concentration. In this paper we summarize the current knowledge on the cyclic nucleotide effectors, focusing both on their structure and functioning in plant cells

Treatment of Winter Wheat (Triticum aestivum L.) Seeds with Electromagnetic Field Influences Germination and Phytohormone Balance Depending on Seed Size

Electromagnetic field (EMF) and its effect on crop plant growth and their quality parameters is increasingly gaining the interest of researchers in agronomic science. However, the exact mechanism of EMF action in plant cells is still unclear. Among the completely unexplored parameters is the relationship between the EMF effects and the seed size. Thus, the EMF effect was analyzed in winter wheat seeds categorized into two size groups, small and big. The study focused on the germination kinetics, early growth parameters, and phytohormone concentrations (indole-3-acetic acid, IAA and abscisic acid, ABA) in seeds, roots, and coleoptiles after exposure to EMFs (50 Hz, 7 mT) and their controls. EMF exposure resulted in faster germination and the more rapid early growth of organs, especially in big seeds in dark conditions. The faster germination and seedling growth of small seeds in control conditions, and of big seeds after EMF exposure, corresponds largely to the decline in IAA and ABA levels. This study confirms that presowing treatment with an EMF is a promising tool for sustainable seed crop improvement, but detailed studies on the EMF mechanism of action, including phytohormones, are necessary to better control future crop yield, especially considering the factor of seed size

Treatment of Winter Wheat (<i>Triticum aestivum</i> L.) Seeds with Electromagnetic Field Influences Germination and Phytohormone Balance Depending on Seed Size

Electromagnetic field (EMF) and its effect on crop plant growth and their quality parameters is increasingly gaining the interest of researchers in agronomic science. However, the exact mechanism of EMF action in plant cells is still unclear. Among the completely unexplored parameters is the relationship between the EMF effects and the seed size. Thus, the EMF effect was analyzed in winter wheat seeds categorized into two size groups, small and big. The study focused on the germination kinetics, early growth parameters, and phytohormone concentrations (indole-3-acetic acid, IAA and abscisic acid, ABA) in seeds, roots, and coleoptiles after exposure to EMFs (50 Hz, 7 mT) and their controls. EMF exposure resulted in faster germination and the more rapid early growth of organs, especially in big seeds in dark conditions. The faster germination and seedling growth of small seeds in control conditions, and of big seeds after EMF exposure, corresponds largely to the decline in IAA and ABA levels. This study confirms that presowing treatment with an EMF is a promising tool for sustainable seed crop improvement, but detailed studies on the EMF mechanism of action, including phytohormones, are necessary to better control future crop yield, especially considering the factor of seed size

In Vitro Characterization of Guanylyl Cyclase BdPepR2 from Brachypodium distachyon Identified through a Motif-Based Approach

In recent years, cyclic guanosine 3′,5′-cyclic monophosphate (cGMP) and guanylyl cyclases (GCs), which catalyze the formation of cGMP, were implicated in a growing number of plant processes, including plant growth and development and the responses to various stresses. To identify novel GCs in plants, an amino acid sequence of a catalytic motif with a conserved core was designed through bioinformatic analysis. In this report, we describe the performed analyses and consider the changes caused by the introduced modification within the GC catalytic motif, which eventually led to the description of a plasma membrane receptor of peptide signaling molecules—BdPepR2 in Brachypodium distachyon. Both in vitro GC activity studies and structural and docking analyses demonstrated that the protein could act as a GC and contains a highly conserved 14-aa GC catalytic center. However, we observed that in the case of BdPepR2, this catalytic center is altered where a methionine instead of the conserved lysine or arginine residues at position 14 of the motif, conferring higher catalytic activity than arginine and alanine, as confirmed through mutagenesis studies. This leads us to propose the expansion of the GC motif to cater for the identification of GCs in monocots. Additionally, we show that BdPepR2 also has in vitro kinase activity, which is modulated by cGMP