scholarly journals Annexins - calcium- and membrane-binding proteins in the plant kingdom: potential role in nodulation and mycorrhization in Medicago truncatula.

2009 ◽  
Vol 56 (2) ◽  
Author(s):  
Tanuja Talukdar ◽  
Karolina Maria Gorecka ◽  
Fernanda De Carvalho-Niebel ◽  
J Allan Downie ◽  
Julie Cullimore ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Medicago Truncatula ◽  
Binding Proteins ◽  
Potential Role ◽  
Mycorrhizal Fungus ◽  
Calcium Signal ◽  
Dependent Manner ◽  
Calcium Response ◽  
Nod Factor

Annexins belong to a family of multi-functional membrane- and Ca(2+)-binding proteins. The characteristic feature of these proteins is that they can bind membrane phospholipids in a reversible, Ca(2+)-dependent manner. While animal annexins have been known for a long time and are fairly well characterized, their plant counterparts were discovered only in 1989, in tomato, and have not been thoroughly studied yet. In the present review, we discuss the available information about plant annexins with special emphasis on biochemical and functional properties of some of them. In addition, we propose a link between annexins and symbiosis and Nod factor signal transduction in the legume plant, Medicago truncatula. A specific calcium response, calcium spiking, is an essential component of the Nod factor signal transduction pathway in legume plants. The potential role of annexins in the generation and propagation of this calcium signal is considered in this review. M. truncatula annexin 1 (MtAnn1) is a typical member of the plant annexin family, structurally similar to other members of the family. Expression of the MtAnn1 gene is specifically induced during symbiotic associations with both Sinorhizobium meliloti and the mycorrhizal fungus Glomus intraradices. Furthermore, it has been reported that the MtAnn1 protein is preferentially localized at the nuclear periphery of rhizobial-activated cortical cells, suggesting a possible role of this annexin in the calcium response signal elicited by symbiotic signals from rhizobia and mycorrhizal fungi.

scholarly journals Epidermal growth factor and Ras regulate gene expression in GH4 pituitary cells by separate, antagonistic signal transduction pathways.

1995 ◽  
Vol 15 (12) ◽  
pp. 6777-6784 ◽  
Author(s):  
C A Pickett ◽  
A Gutierrez-Hartmann
Keyword(s):  
Signal Transduction ◽  
Transcription Factors ◽  
Growth Factor ◽  
Map Kinase ◽  
Dominant Negative ◽  
Neuroendocrine Cells ◽  
Dependent Manner ◽  
Epidermal Growth ◽  
Dose Dependent

We have previously demonstrated that epidermal growth factor (EGF) produces activation of the rat prolactin (rPRL) promoter in GH4 neuroendocrine cells via a Ras-independent mechanism. This Ras independence of the EGF response appears to be cell rather than promoter specific. Oncogenic Ras also produces activation of the rPRL promoter when transfected into GH4 cells and requires the sequential activation of Raf kinase, mitogen-activated protein (MAP) kinase, and c-Ets-1/GHF-1 to mediate this response. In these studies, we have investigated the interaction between EGF and Ras in stimulating rPRL promoter activity and the role of Raf and MAP kinases in mediating the EGF response. We have also examined the role of several transcription factors and used various promoter mutants of the rPRL gene in order to better define the trans- and cis-acting components of the EGF response. EGF treatment of GH4 cells inhibits activation of the rPRL promoter produced by transfection of V12Ras from 24- to 4-fold in an EGF dose-dependent manner. This antagonistic effect of EGF and Ras is mutual in that transfection of V12Ras also blocks EGF-induced activation of the rPRL promoter in a Ras dose-dependent manner, from 5.5- to 1.6-fold. Transfection of a plasmid encoding the dominant-negative Raf C4 blocks Ras-induced activation by 66% but fails to inhibit EGF-mediated activation of the rPRL promoter. Similarly, transfection of a construct encoding an inhibitory form of MAP kinase decreases the Ras response by 50% but does not inhibit the EGF response. Previous studies have demonstrated that c-Ets-1 is necessary and that GHF-1 acts synergistically with c-Ets-1 in the Ras response of the rPRL promoter. In contrast, overexpression of neither c-Ets-1 nor GHF-1 enhanced EGF-mediated activation of the rPRL promoter, and dominant-negative forms of these transcription factors failed to inhibit the EGF response. Using 5' deletion and site-specific mutations, we have mapped the EGF response to two regions on the proximal rPRL promoter. One region maps between -255 and -212, near the Ras response element, and a second maps between -125 and -54. The latter region appears to involve footprint 2, a previously identified repressor site on the rPRL promoter. Neither footprint 1 nor 3, known GHF-1 binding sites, appears to be crucial to RGF-mediated rPRL promoter activation. The results of these studies indicate that in GH4 neuroendocrine cells, rPRL gene regulation by EGF is mediated by a signal transduction pathway that is separate and antagonistic to the Ras pathway. Hence, the functional role of the Ras/Raf/MAP kinase pathway in mediating transcriptional responses to EGF and other receptor tyrosine kinase may differ in highly specialized cell types.

scholarly journals Expression of small GTPases in the roots and nodules of Medicago truncatula cv. Jemalong

2019 ◽  
Vol 78 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Abdul Razaque Memon ◽  
Christiane Katja Schwager ◽  
Karsten Niehaus
Keyword(s):  
Medicago Truncatula ◽  
Binding Proteins ◽  
Polymerase Chain Reaction Analysis ◽  
Small Gtpases ◽  
Infection Process ◽  
Nodule Development ◽  
Gtp Binding Proteins ◽  
Gtp Binding ◽  
Differential Expression Pattern

Abstract In this study we used Medicago truncatula, to identify and analyze the expression of small GTP-binding proteins (Arf1, Arl1, Sar1, Rabs, Rop/Rac) and their interacting partners in the infection process in the roots and nodules. A real-time polymerase chain reaction analysis was carried out and our results showed that Arf1 (AtArfB1c-like), MtSar1, AtRabA1e-like, AtRabC1-like, MsRab11-like and AtRop7-like genes were highly expressed in the nodules of rhizobium inoculated plants compared to the non-inoculated ones. On the contrary, AtRabA3 like, AtRab5c and MsRac1-like genes were highly expressed in non-infected nitrogen supplied roots of M. truncatula. Other Rab genes (AtRabA4a, AtRabA4c and AtRabG3a-like genes) were nearly equally expressed in both treatments. Interestingly, RbohB (a respiratory burst NADPH oxidase homologue) was more highly expressed in rhizobium infected than in non-infected roots and nodules. Our data show a differential expression pattern of small GTP-binding proteins in roots and nodules of the plants. This study demonstrates an important role of small GTP-binding proteins in symbiosome biogenesis and root nodule development in legumes.

scholarly journals The action of α-adrenergic agonists on plasma-membrane calcium fluxes in perfused rat liver

1984 ◽  
Vol 220 (1) ◽  
pp. 43-50 ◽  
Author(s):  
P H Reinhart ◽  
W M Taylor ◽  
F L Bygrave
Keyword(s):  
Plasma Membrane ◽  
Rat Liver ◽  
Potential Role ◽  
Dependent Manner ◽  
Perfused Rat Liver ◽  
Adrenergic Agonists ◽  
Mediated Effects ◽  
Alpha Agonist ◽  
Alpha Adrenergic Agonist

The effect of alpha-adrenergic agonists on Ca2+ fluxes was examined in the perfused rat liver by using a combination of Ca2+-electrode and 45Ca2+-uptake techniques. We showed that net Ca2+ fluxes can be described by the activities of separate Ca2+-uptake and Ca2+-efflux components, and that alpha-adrenergic agonists modulate the activity of both components in a time-dependent manner. Under resting conditions, Ca2+-uptake and -efflux activities are balanced, resulting in Ca2+ cycling across the plasma membrane. The alpha-adrenergic agonists vasopressin and angiotensin, but not glucagon, stimulate the rate of both Ca2+ efflux and Ca2+ uptake. During the first 2-3 min of alpha-agonist administration the effect on the efflux component is the greater, the net effect being efflux of Ca2+ from the cell. After 3-4 min of phenylephrine treatment, net Ca2+ movements are essentially complete, however, the rate of Ca2+ cycling is significantly increased. After removal of the alpha-agonist a large stimulation of the rate of Ca2+ uptake leads to the net accumulation of Ca2+ by the cell. The potential role of these Ca2+ flux changes in the expression of alpha-adrenergic-agonist-mediated effects is discussed.

scholarly journals Quorum-sensing regulation in rhizobia and its role in symbiotic interactions with legumes

2007 ◽  
Vol 362 (1483) ◽  
pp. 1149-1163 ◽  
Author(s):  
Maria Sanchez-Contreras ◽  
Wolfgang D Bauer ◽  
Mengsheng Gao ◽  
Jayne B Robinson ◽  
J Allan Downie
Keyword(s):  
Quorum Sensing ◽  
Potential Role ◽  
Active Role ◽  
Dependent Manner ◽  
Homoserine Lactones ◽  
Signalling Molecules ◽  
Sensing Systems ◽  
Symbiotic Interactions ◽  
Regulatory Systems

Legume-nodulating bacteria (rhizobia) usually produce N -acyl homoserine lactones, which regulate the induction of gene expression in a quorum-sensing (or population-density)-dependent manner. There is significant diversity in the types of quorum-sensing regulatory systems that are present in different rhizobia and no two independent isolates worked on in detail have the same complement of quorum-sensing genes. The genes regulated by quorum sensing appear to be rather diverse and many are associated with adaptive aspects of physiology that are probably important in the rhizosphere. It is evident that some aspects of rhizobial physiology related to the interaction between rhizobia and legumes are influenced by quorum sensing. However, it also appears that the legumes play an active role, both in terms of interfering with the rhizobial quorum-sensing systems and responding to the signalling molecules made by the bacteria. In this article, we review the diversity of quorum-sensing regulation in rhizobia and the potential role of legumes in influencing and responding to this signalling system.

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