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vegetative function [keywords]
- The Adenylyl Cyclase Plays a Regulatory Role in the Morphogenetic Switch from Vegetative to Pathogenic Lifestyle of Fusarium graminearum on Wheat. [Journal Article]
- PLoS One 2014; 9(3):e91135.
Cyclic 3',5'-adenosine monophosphate (cAMP) is a nucleotide derived from adenosine triphosphate that acts as a second messenger throughout all kingdoms. Intracellular cAMP levels are synthesized by a membrane-bound protein, the adenylyl cyclase. In order to analyze the function of this gene and the importance of cAMP in the life cycle of the cereal pathogen Fusarium graminearum, the adenylyl cyclase gene (FGSG_01234) was deleted by gene replacement (ΔFgac1). The ΔFgac1 mutant displayed a drastically reduced growth on agar medium which could be rescued by a cAMP analogon. Furthermore, the ΔFgac1 mutant was unable to produce perithecia on detached wheat nodes. However, artificial conditions like carrot agar allowed perithecia development. Pathogenicity towards wheat was drastically reduced in ΔFgac1 compared to the wild type. Point-inoculated spikelets showed only small lesions but no typical head blight disease symptoms. Fluorescence microscopy using dsRed-expressing strains revealed that the ΔFgac1 strain was unable to develop any complex infection structures like lobate appressoria and infection cushions. Instead, hyphal anastomosis occurs frequently. Scanning electron microscopy demonstrated the lack of fungal penetration. Hence, the formation of compound appressoria seems to be essential for infection of wheat. Hyphae on flower leaves produced huge amounts of new conidia, thereby circumventing the infection cycle. This abundant sporulation on wheat epidermis was not observed in wild type. Intriguingly, the Fgac1 deletion mutant was able to infect maize cobs as wild type, indicating that cAMP signaling is not important for maize infection. The ΔFgac1 mutant was unable to produce the mycotoxin deoxynivalenol both in vitro and during wheat infection. In this study, we show that cAMP signaling controls important cellular processes such as development of infection structures, pathogenicity, secondary metabolite production and sexual reproduction. For the first time, we show that cAMP regulates the switch from vegetative to pathogenic lifestyle of F. graminearum on wheat.
- Co-overexpression of two Heat Shock Factors results in enhanced seed longevity and in synergistic effects on seedling tolerance to severe dehydration and oxidative stress. [JOURNAL ARTICLE]
- BMC Plant Biol 2014 Mar 4; 14(1):56.
We have previously reported that the seed-specific overexpression of sunflower (Helianthus annuus L.) Heat Shock Factor A9 (HaHSFA9) enhanced seed longevity in transgenic tobacco (Nicotiana tabacum L.). In addition, the overexpression of HaHSFA9 in vegetative organs conferred tolerance to drastic levels of dehydration and oxidative stress.Here we found that the combined overexpression of sunflower Heat Shock Factor A4a (HaHSFA4a) and HaHSFA9 enhanced all the previously reported phenotypes described for the overexpression of HaHSFA9 alone. The improved phenotypes occurred in coincidence with only subtle changes in the accumulation of small Heat Shock Proteins (sHSP) that are encoded by genes activated by HaHSFA9. The single overexpression of HaHSFA4a in vegetative organs (which lack endogenous HSFA9 proteins) did not induce sHSP accumulation under control growth conditions; neither it conferred thermotolerance. The overexpression of HaHSFA4a alone also failed to induce tolerance to severe abiotic stress. Thus, a synergistic functional effect of both factors was evident in seedlings.Our study revealed that HaHSFA4a requires HaHSFA9 for in planta function. Our results strongly support the involvement of HaHSFA4a and HaHSFA9 in transcriptional co-activation of a genetic program of longevity and desiccation tolerance in sunflower seeds. These results would also have potential application for improving seed longevity and tolerance to severe stress in vegetative organs.
- Growing evening primroses (Oenothera). [REVIEW]
- Front Plant Sci 2014.:38.
The model plant Oenothera has contributed significantly to the biological sciences and it dominated the early development of plant genetics, cytogenetics, and evolutionary biology. The great advantage of using Oenothera as a model system is a large body of genetic, cytological, morphological, and ecological information collected over more than a century. The Oenothera system offers a well-studied taxonomy, population structure, and ecology. Cytogenetics and formal genetics at the population level are extensively developed, providing an excellent basis to study evolutionary questions. Further, Oenothera is grown as an oil seed crop for the production of essential fatty acids (gamma-linoleic acid) and is considered to be a medicinal plant due to its many pharmaceutically active secondary metabolites, such as ellagitannins. Although Oenothera has been cultivated as a laboratory organism since the end of the 19th century, there is a substantial lack of literature dealing with modern greenhouse techniques for the genus. This review compiles an overview about the growth requirements for the genus Oenothera, with a special focus on its genetically best-studied subsections Oenothera and Munzia. Requirements for greenhouse, field, and agronomic cultures are presented, together with information on substrate types, pest control, as well as vegetative and seed propagation, cross pollination, harvest, and seed storage. Particular aspects like germination, bolting, and flowering induction in taxonomically diverse material are reviewed. Methods recommended are supported by ecological and experimental data. An overview of the possibilities for wide hybridization and polyploidy induction in the genus is given. Germplasm resources are referenced. In summary, a comprehensive guideline for successful laboratory cultivation of Oenothera species is provided.
- Changes in arterial function in a mouse model of human familial hypercholesterolemia. [JOURNAL ARTICLE]
- Acta Physiol (Oxf) 2014 Feb 26.
Atherosclerosis is the most common cause of cardiovascular disease. The ApoB mouse is a model for human familial hypercholesterolemia and has a lipoprotein profile similar to that of humans with atherosclerosis. Therefore, it is a suitable model to investigate the changes in vasoreactivity during atherogenesis. This study investigates contractile and dilatative properties of arteries in this model in relation to age.Male ApoB mice and B6, WT, mice were examined at age 4 or 18 month. Isometric measurements of 2 mm ring preparations of the aorta thoracica were performed by using a wire myograph. Histological and biochemical methods served to determine atherosclerosis, lipid status and endothelial markers, respectively.Morphometric analysis showed that all old ApoB mice had severe atherosclerosis in the aorta. Atherosclerotic alteration of the aorta of the ApoB mice coincided with a diminished vasodilatation to acetylcholine. The phenylephrine response was significantly attenuated already to the same degree in the non-atherosclerotic aorta of the young ApoB mice as in the atherosclerotic aorta of the older ApoB mice. Serum parameters showed a rise in total cholesterol and triglycerides in the ApoB strain compared to WT mice. sICAM-1 and sVCAM-1 were increased in old compared to young ApoB mice.The study shows that reduced acetylcholine-induced dilatation is related to the presence of atherosclerosis in old ApoB mice. Remarkably, the impaired vessel reactivity to phenylephrine already in young ApoB mice indicates early changes in vascular function in this model. This article is protected by copyright. All rights reserved.
- Outline of therapeutic interventions with muscarinic receptor-mediated transmission. [Journal Article]
- Physiol Res 2014 Feb 24.:S177-89.
Muscarinc receptor-mediated signaling takes part in many physiological functions ranging from complex higher nervous activity to vegetative responses. Specificity of action of the natural muscarinic agonist acetylcholine is effected by action on five muscarinic receptor subtypes with particular tissue and cellular localization, and coupling preference with different G-proteins and their signaling pathways. In addition to physiological roles it is also implicated in pathologic events like promotion of carcinoma cells growth, early pathogenesis of neurodegenerative diseases in the central nervous system like Alzheimer´s disease and Parkinson´s disease, schizophrenia, intoxications resulting in drug addiction, or overactive bladder in the periphery. All of these disturbances demonstrate involvement of specific muscarinic receptor subtypes and point to the importance to develop selective pharmacotherapeutic interventions. Because of the high homology of the orthosteric binding site of muscarinic receptor subtypes there is virtually no subtype selective agonist that binds to this site. Activation of specific receptor subtypes may be achieved by developing allosteric modulators of acetylcholine binding, since ectopic binding domains on the receptor are less conserved compared to the orthosteric site. Potentiation of the effects of acetylcholine by allosteric modulators would be beneficial in cases where acetylcholine release is reduced due to pathological conditions. When presynaptic function is severly compromised, the utilization of ectopic agonists can be a thinkable solution.
- Meristem-specific expression of epigenetic regulators safeguards transposon silencing in Arabidopsis. [JOURNAL ARTICLE]
- EMBO Rep 2014 Feb 20.
In plants, transposable elements (TEs) are kept inactive by transcriptional gene silencing (TGS). TGS is established and perpetuated by RNA-directed DNA methylation (RdDM) and maintenance methylation pathways, respectively. Here, we describe a novel RdDM function specific for shoot apical meristems that reinforces silencing of TEs during early vegetative growth. In meristems, RdDM counteracts drug-induced interference with TGS maintenance and consequently prevents TE activation. Simultaneous disturbance of both TGS pathways leads to transcriptionally active states of repetitive sequences that are inherited by somatic tissues and partially by the progeny. This apical meristem-specific mechanism is mediated by increased levels of TGS factors and provides a checkpoint for correct epigenetic inheritance during the transition from vegetative to reproductive phase and to the next generation.
- Adventitious Roots and Lateral Roots: Similarities and Differences. [JOURNAL ARTICLE]
- Annu Rev Plant Biol 2014 Feb 7.
In addition to its role in water and nutrient uptake, the root system is fundamentally important because it anchors a plant to its substrate. Although a wide variety of root systems exist across different species, all plants have a primary root (derived from an embryonic radicle) and different types of lateral roots. Adventitious roots, by comparison, display the same functions as lateral roots but develop from aerial tissues. In addition, they not only develop as an adaptive response to various stresses, such as wounding or flooding, but also are a key limiting component of vegetative propagation. Lateral and adventitious roots share key elements of the genetic and hormonal regulatory networks but are subject to different regulatory mechanisms. In this review, we discuss the developmental processes that give rise to lateral and adventitious roots and highlight knowledge acquired over the past few years about the mechanisms that regulate adventitious root formation. Expected final online publication date for the Annual Review of Plant Biology Volume 65 is April 29, 2014. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.
- The putative PRC1 RING-finger protein AtRING1A regulates flowering through repressing MADS AFFECTING FLOWERING genes in Arabidopsis. [Journal Article]
- Development 2014 Mar; 141(6):1303-12.
Polycomb group proteins play essential roles in the epigenetic control of gene expression in plants and animals. Although some components of Polycomb repressive complex 1 (PRC1)-like complexes have recently been reported in the model plant Arabidopsis, how they contribute to gene repression remains largely unknown. Here we show that a putative PRC1 RING-finger protein, AtRING1A, plays a hitherto unknown role in mediating the transition from vegetative to reproductive development in Arabidopsis. Loss of function of AtRING1A results in the late-flowering phenotype, which is attributed to derepression of two floral repressors, MADS AFFECTING FLOWERING 4/5 (MAF4/5), which in turn downregulate two floral pathway integrators, FLOWERING LOCUS T and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1. Levels of the H3K27me3 repressive mark at MAF4 and MAF5 loci, which is deposited by CURLY LEAF (CLF)-containing PRC2-like complexes and bound by LIKE HETEROCHROMATIN PROTEIN 1 (LHP1), are affected by AtRING1A, which interacts with both CLF and LHP1. Levels of the H3K4me3 activation mark correlate inversely with H3K27me3 levels at MAF4 and MAF5 loci. Our results suggest that AtRING1A suppresses the expression of MAF4 and MAF5 through affecting H3K27me3 levels at these loci to regulate the floral transition in Arabidopsis.
- Auxin is a central player in the hormone cross-talks that control adventitious rooting. [JOURNAL ARTICLE]
- Physiol Plant 2014 Feb 18.
Vegetative propagation of economically important woody, horticultural and agricultural species rely on an efficient adventitious root (AR) formation. The formation of adventitious roots is a complex genetic trait regulated by the interaction of environmental and endogenous factors among which the phytohormone auxin plays an essential role. This review summarizes the current knowledge related to the intricate network through which auxin controls adventitious rooting. How auxin and recently identified auxin-related compounds affect AR formation in different plant species is discussed. Particular attention is addressed to illustrate how auxin has a central role in the hormone cross-talk leading to AR development. In parallel, we describe the molecular players involved in the control of auxin homeostasis, transport and signaling, for a better understanding of the auxin action during adventitious rooting.
- Development- and cold-regulated accumulation of cold shock domain proteins in wheat. [JOURNAL ARTICLE]
- Plant Physiol Biochem 2014 Feb 1.:44-48.
Cold shock domain (CSD) proteins, or Y-box proteins, are nucleic acid-binding proteins that are widely distributed from bacteria to higher plants and animals. Bacterial CSD proteins play an essential role in cold adaptation by destabilizing RNA secondary structures. WHEAT COLD SHOCK DOMAIN PROTEIN 1 (WCSP1) shares biochemical functions with bacterial CSD proteins and is possibly involved in cold adaptation. In this study, the temporal and spatial distribution of the wheat cold shock domain protein family (WCSPs) was serologically characterized with regard to plant development and cold adaptation. Four WCSP genes were identified through database analysis and were classified into three classes based on their molecular masses and protein domain structures. Class I (20 kD) and class II (23 kD) WCSPs demonstrated a clear pattern of accumulation in root and shoot meristematic tissues during vegetative growth. In response to cold, marked increases in WCSP levels were observed but the pattern of accumulation differed by tissue. Accumulation of WCSPs in crown tissue during cold acclimation was observed in the winter cultivar 'Chihokukomugi' but not in the spring cultivar 'Haruyutaka', suggesting a possible function for WCSPs in cold acclimation. During flower and seed development, protein levels of class I and class II WCSPs remained high. The class III WCSP (27 kD) was detected only during seed development. The highest level of class III WCSP accumulation was observed at the milky seed stage. Together, the results of this study provide a view of CSD protein accumulation throughout the life cycle of wheat and suggest that WCSPs function differentially in plant development and cold adaptation.