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Plants, Volume 3, Issue 3 (September 2014) – 8 articles , Pages 304-457

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1609 KiB  
Article
Live Cell Imaging During Germination Reveals Dynamic Tubular Structures Derived from Protein Storage Vacuoles of Barley Aleurone Cells
by Verena Ibl and Eva Stoger
Plants 2014, 3(3), 442-457; https://doi.org/10.3390/plants3030442 - 05 Sep 2014
Cited by 6 | Viewed by 9550
Abstract
The germination of cereal seeds is a rapid developmental process in which the endomembrane system undergoes a series of dynamic morphological changes to mobilize storage compounds. The changing ultrastructure of protein storage vacuoles (PSVs) in the cells of the aleurone layer has been [...] Read more.
The germination of cereal seeds is a rapid developmental process in which the endomembrane system undergoes a series of dynamic morphological changes to mobilize storage compounds. The changing ultrastructure of protein storage vacuoles (PSVs) in the cells of the aleurone layer has been investigated in the past, but generally this involved inferences drawn from static pictures representing different developmental stages. We used live cell imaging in transgenic barley plants expressing a TIP3-GFP fusion protein as a fluorescent PSV marker to follow in real time the spatially and temporally regulated remodeling and reshaping of PSVs during germination. During late-stage germination, we observed thin, tubular structures extending from PSVs in an actin-dependent manner. No extensions were detected following the disruption of actin microfilaments, while microtubules did not appear to be involved in the process. The previously-undetected tubular PSV structures were characterized by complex movements, fusion events and a dynamic morphology. Their function during germination remains unknown, but might be related to the transport of solutes and metabolites. Full article
(This article belongs to the Special Issue Plant Vacuole)
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768 KiB  
Article
Calmodulin Gene Expression in Response to Mechanical Wounding and Botrytis cinerea Infection in Tomato Fruit
by Hui Peng, Tianbao Yang and Wayne M. Jurick II
Plants 2014, 3(3), 427-441; https://doi.org/10.3390/plants3030427 - 29 Aug 2014
Cited by 21 | Viewed by 8968
Abstract
Calmodulin, a ubiquitous calcium sensor, plays an important role in decoding stress-triggered intracellular calcium changes and regulates the functions of numerous target proteins involved in various plant physiological responses. To determine the functions of calmodulin in fleshy fruit, expression studies were performed on [...] Read more.
Calmodulin, a ubiquitous calcium sensor, plays an important role in decoding stress-triggered intracellular calcium changes and regulates the functions of numerous target proteins involved in various plant physiological responses. To determine the functions of calmodulin in fleshy fruit, expression studies were performed on a family of six calmodulin genes (SlCaMs) in mature-green stage tomato fruit in response to mechanical injury and Botrytis cinerea infection. Both wounding and pathogen inoculation triggered expression of all those genes, with SlCaM2 being the most responsive one to both treatments. Furthermore, all calmodulin genes were upregulated by salicylic acid and methyl jasmonate, two signaling molecules involved in plant immunity. In addition to SlCaM2, SlCaM1 was highly responsive to salicylic acid and methyl jasmonate. However, SlCaM2 exhibited a more rapid and stronger response than SlCaM1. Overexpression of SlCaM2 in tomato fruit enhanced resistance to Botrytis-induced decay, whereas reducing its expression resulted in increased lesion development. These results indicate that calmodulin is a positive regulator of plant defense in fruit by activating defense pathways including salicylate- and jasmonate-signaling pathways, and SlCaM2 is the major calmodulin gene responsible for this event. Full article
(This article belongs to the Special Issue Interaction Between Abiotic and Biotic Stresses in Plants)
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20059 KiB  
Article
Vacuolar Na+/H+ NHX-Type Antiporters Are Required for Cellular K+ Homeostasis, Microtubule Organization and Directional Root Growth
by Tyler McCubbin, Elias Bassil, Shiqi Zhang and Eduardo Blumwald
Plants 2014, 3(3), 409-426; https://doi.org/10.3390/plants3030409 - 29 Aug 2014
Cited by 32 | Viewed by 9912
Abstract
Na+/H+ antiporters (NHXs) are integral membrane transporters that catalyze the electroneutral exchange of K+ or Na+ for H+ and are implicated in cell expansion, development, pH and ion homeostasis and salt tolerance. Arabidopsis contains four vacuolar NHX [...] Read more.
Na+/H+ antiporters (NHXs) are integral membrane transporters that catalyze the electroneutral exchange of K+ or Na+ for H+ and are implicated in cell expansion, development, pH and ion homeostasis and salt tolerance. Arabidopsis contains four vacuolar NHX isoforms (NHX1–NHX4), but only the functional roles for NHX1 and NHX2 have been assessed thus far. Colocalization studies indicated that NHX3 and NHX4 colocalize to the tonoplast. To investigate the role of all vacuolar NHX isoforms, a quadruple knockout nhx1nhx2nhx3nhx4, lacking all vacuolar NHXs, was generated. Seedlings of nhx1nhx2nhx3nhx4 displayed significantly reduced growth, with markedly shorter hypocotyls. Under high K+, but not Na+, pronounced root skewing occurred in nhx1nhx2nhx3nhx4, suggesting that the organization of the cytoskeleton might be perturbed. Whole mount immunolabeling of cortical microtubules indicated that high K+ caused significant microtubule reorganization in nhx1nhx2nhx3nhx4 root cells of the elongation zone. Using microtubule stabilizing (Taxol) and destabilizing (propyzamide) drugs, we found that the effect of K+ on nhx1nhx2nhx3nhx4 root growth was antagonistic to that of Taxol, whereas elevated K+ exacerbated the endogenous effect of propyzamide on root skewing. Collectively, our results suggest that altered K+ homeostasis leads to an increase in the dynamics of cortical microtubule reorganization in nhx1nhx2nhx3nhx4 root epidermal cells of the elongation zone. Full article
(This article belongs to the Special Issue Plant Vacuole)
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564 KiB  
Review
Vacuolar Sorting Receptor-Mediated Trafficking of Soluble Vacuolar Proteins in Plant Cells
by Hyangju Kang and Inhwan Hwang
Plants 2014, 3(3), 392-408; https://doi.org/10.3390/plants3030392 - 25 Aug 2014
Cited by 17 | Viewed by 9860
Abstract
Vacuoles are one of the most prominent organelles in plant cells, and they play various important roles, such as degradation of waste materials, storage of ions and metabolites, and maintaining turgor. During the past two decades, numerous advances have been made in understanding [...] Read more.
Vacuoles are one of the most prominent organelles in plant cells, and they play various important roles, such as degradation of waste materials, storage of ions and metabolites, and maintaining turgor. During the past two decades, numerous advances have been made in understanding how proteins are specifically delivered to the vacuole. One of the most crucial steps in this process is specific sorting of soluble vacuolar proteins. Vacuolar sorting receptors (VSRs), which are type I membrane proteins, are involved in the sorting and packaging of soluble vacuolar proteins into transport vesicles with the help of various accessory proteins. To date, large amounts of data have led to the development of two different models describing VSR-mediated vacuolar trafficking that are radically different in multiple ways, particularly regarding the location of cargo binding to, and release from, the VSR and the types of carriers utilized. In this review, we summarize current literature aimed at elucidating VSR-mediated vacuolar trafficking and compare the two models with respect to the sorting signals of vacuolar proteins, as well as the molecular machinery involved in VSR-mediated vacuolar trafficking and its action mechanisms. Full article
(This article belongs to the Special Issue Plant Vacuole)
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1026 KiB  
Article
Expression of the Arabidopsis Sigma Factor SIG5 Is Photoreceptor and Photosynthesis Controlled
by Marina Mellenthin, Ulrike Ellersiek, Anna Börger and Margarete Baier
Plants 2014, 3(3), 359-391; https://doi.org/10.3390/plants3030359 - 18 Aug 2014
Cited by 20 | Viewed by 11100
Abstract
Two collections of Arabidopsis GAL4 enhancer trap lines were screened for light-intensity dependent reporter gene activation. Line N9313 was isolated for its strong light-intensity regulation. The T-DNA element trapped distant enhancers of the SIG5 promoter, which drives expression of a sigma factor involved [...] Read more.
Two collections of Arabidopsis GAL4 enhancer trap lines were screened for light-intensity dependent reporter gene activation. Line N9313 was isolated for its strong light-intensity regulation. The T-DNA element trapped distant enhancers of the SIG5 promoter, which drives expression of a sigma factor involved in regulation of chloroplast genes for photosystem II core proteins. The T-DNA insertion 715 bp upstream of the transcription initiation site splits the promoter in a distal and proximal part. Both parts are sensitive to blue and red light and depend on photosynthetic electron transport activity between photosystem II and the plastoquinone pool. The mainblue-light sensitivity is localized within a 196-bp sequence (–887 to –691 bp) in the proximal promoter region It is preferentially CRY1 and PHYB controlled. Type-I and type-II phytochromes mediate red-light sensitivity via various promoter elements spread over the proximal and distal upstream region. This work characterizes SIG5 as an anterograde control factor of chloroplast gene expression, which is controlled by chloroplast signals in a retrograde manner. Full article
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979 KiB  
Article
The Half-Size ABC Transporter FOLDED PETALS 2/ABCG13 Is Involved in Petal Elongation through Narrow Spaces in Arabidopsis thaliana Floral Buds
by Seiji Takeda, Akira Iwasaki, Kiyoshi Tatematsu and Kiyotaka Okada
Plants 2014, 3(3), 348-358; https://doi.org/10.3390/plants3030348 - 15 Aug 2014
Cited by 12 | Viewed by 7866
Abstract
Flowers are vital for attracting pollinators to plants and in horticulture for humans. Petal morphogenesis is a central process of floral development. Petal development can be divided into three main processes: the establishment of organ identity in a concentric pattern, primordia initiation at [...] Read more.
Flowers are vital for attracting pollinators to plants and in horticulture for humans. Petal morphogenesis is a central process of floral development. Petal development can be divided into three main processes: the establishment of organ identity in a concentric pattern, primordia initiation at fixed positions within a whorl, and morphogenesis, which includes petal elongation through the narrow spaces within the bud. Here, we show that the FOLDED PETALS 2 (FOP2) gene, encoding a member of the half-size ATP binding cassette (ABC) transporter family ABCG13, is involved in straight elongation of petals in Arabidopsis thaliana. In fop2 mutants, flowers open with folded petals, instead of straight-elongated ones found in the wild type. The epicuticular nanoridge structures are absent in many abaxial epidermal cells of fop2 petals, and surgical or genetic generation of space in young fop2 buds restores the straight elongation of petals, suggesting that the physical contact of sepals and petals causes the petal folding. Similar petal folding has been reported in the fop1 mutant, and the petals of fop2 fop1 double mutants resemble those of both the fop1 and fop2 single mutants, although the epidermal structure and permeability of the petal surface is more affected in fop2. Our results suggest that synthesis and transport of cutin or wax in growing petals play an important role for their smooth elongation through the narrow spaces of floral buds. Full article
(This article belongs to the Special Issue Plant Reproductive Transition and Flower Development)
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2380 KiB  
Article
Characterization of Four Bifunctional Plant IAM/PAM-Amidohydrolases Capable of Contributing to Auxin Biosynthesis
by Beatriz Sánchez-Parra, Henning Frerigmann, Marta-Marina Pérez Alonso, Víctor Carrasco Loba, Ricarda Jost, Mathias Hentrich and Stephan Pollmann
Plants 2014, 3(3), 324-347; https://doi.org/10.3390/plants3030324 - 07 Aug 2014
Cited by 22 | Viewed by 10759
Abstract
Amidases [EC 3.5.1.4] capable of converting indole-3-acetamide (IAM) into the major plant growth hormone indole-3-acetic acid (IAA) are assumed to be involved in auxin de novo biosynthesis. With the emerging amount of genomics data, it was possible to identify over forty proteins with [...] Read more.
Amidases [EC 3.5.1.4] capable of converting indole-3-acetamide (IAM) into the major plant growth hormone indole-3-acetic acid (IAA) are assumed to be involved in auxin de novo biosynthesis. With the emerging amount of genomics data, it was possible to identify over forty proteins with substantial homology to the already characterized amidases from Arabidopsis and tobacco. The observed high conservation of amidase-like proteins throughout the plant kingdom may suggest an important role of theses enzymes in plant development. Here, we report cloning and functional analysis of four, thus far, uncharacterized plant amidases from Oryza sativa, Sorghum bicolor, Medicago truncatula, and Populus trichocarpa. Intriguingly, we were able to demonstrate that the examined amidases are also capable of converting phenyl-2-acetamide (PAM) into phenyl-2-acetic acid (PAA), an auxin endogenous to several plant species including Arabidopsis. Furthermore, we compared the subcellular localization of the enzymes to that of Arabidopsis AMI1, providing further evidence for similar enzymatic functions. Our results point to the presence of a presumably conserved pathway of auxin biosynthesis via IAM, as amidases, both of monocot, and dicot origins, were analyzed. Full article
(This article belongs to the Special Issue Auxin Signaling, Transport, and Metabolism)
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790 KiB  
Article
Shielding Flowers Developing under Stress: Translating Theory to Field Application
by Noam Chayut, Shiri Sobol, Nahum Nave and Alon Samach
Plants 2014, 3(3), 304-323; https://doi.org/10.3390/plants3030304 - 11 Jul 2014
Cited by 6 | Viewed by 7125
Abstract
Developing reproductive organs within a flower are sensitive to environmental stress. A higher incidence of environmental stress during this stage of a crop plants’ developmental cycle will lead to major breaches in food security. Clearly, we need to understand this sensitivity and try [...] Read more.
Developing reproductive organs within a flower are sensitive to environmental stress. A higher incidence of environmental stress during this stage of a crop plants’ developmental cycle will lead to major breaches in food security. Clearly, we need to understand this sensitivity and try and overcome it, by agricultural practices and/or the breeding of more tolerant cultivars. Although passion fruit vines initiate flowers all year round, flower primordia abort during warm summers. This restricts the season of fruit production in regions with warm summers. Previously, using controlled chambers, stages in flower development that are sensitive to heat were identified. Based on genetic analysis and physiological experiments in controlled environments, gibberellin activity appeared to be a possible point of horticultural intervention. Here, we aimed to shield flowers of a commercial cultivar from end of summer conditions, thus allowing fruit production in new seasons. We conducted experiments over three years in different settings, and our findings consistently show that a single application of an inhibitor of gibberellin biosynthesis to vines in mid-August can cause precocious flowering of ~2–4 weeks, leading to earlier fruit production of ~1 month. In this case, knowledge obtained on phenology, environmental constraints and genetic variation, allowed us to reach a practical solution. Full article
(This article belongs to the Special Issue Plant Reproductive Transition and Flower Development)
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