Dynamic Light Regulation of Translation Status in Arabidopsis thaliana

Light, a dynamic environmental parameter, is an essential regulator of plant growth and development. Light-regulated transcriptional networks are well documented, whereas light-regulated post-transcriptional regulation has received limited attention. In this study, dynamics in translation of cytosolic mRNAs were evaluated at the genome-level in Arabidopsis thaliana seedlings grown under a typical light/dark diurnal regime, shifted to darkness at midday, and then re-illuminated. One-hour of unanticipated darkness reduced levels of polysomes by 17% in a manner consistent with inhibition of initiation of translation. This down-regulation of translation was reversed within 10 min of re-illumination. Quantitative comparison of the total cellular population of transcripts (the transcriptome) to those associated with one or more 80S ribosome (the translatome) identified over 1600 mRNAs that were differentially translated in response to light availability. Unanticipated darkness limited both transcription and translation of mRNAs encoding components of the photosynthetic machinery. Many mRNAs encoding proteins associated with the energy demanding process of protein synthesis were stable but sequestered in the dark, in a rapidly reversible manner. A meta-analysis determined these same transcripts were similarly and coordinately regulated in response to changes in oxygen availability. The dark and hypoxia translationally repressed mRNAs lack highly supported candidate RNA-regulatory elements but are characterized by G + C-rich 5′-untranslated regions. We propose that modulation of translation of a subset of cellular mRNAs functions as an energy conservation mechanism

Utilization Feasibility of Emulsifying Polymers in Cream Base

ABSTRACTObjective: Emulsifying polymer has been employed for low energy emulsification. This study investigated effect of some crucial factorson the physical properties of cream prepared from these polymers. Method: Systems containing various emulsifying polymers, distilledwater and isopropyl isostearate were prepared. Formula and process variables including type and amount of emulsifying polymer, typeand amount of solvents, and order of mixing on physical properties of cream base, were evaluated. Results: Viscosity of emulsions wasincreased as amount of emulsifying polymer was increased. Additionally, viscosity of systems depended on the type of emulsifyingpolymer and the type of solvent. Viscosity of formulation was different as order of mixing was changed. Conclusion: Type and amount ofemulsifying polymers or solvent and order of mixing notably affected viscosity of cream base. However, these polymeric emulsifiers havepotential use for emulsion both in pharmaceutical and cosmetic products.Keywords: cream base, emulsifying polymers, utilizationThai Pharm Health Sci J 2009;4(4):456-462

Isolation and molecular identification of β-carotene producing strains of Dunaliella salina and Dunaliella bardawil from salt soil samples by using species-specific primers and internal transcribed spacer (ITS) primers

Dunaliella salina and Dunaliella bardawil are unique species of the genus Dunaliella that produce large amounts of â-carotene when cultivated under appropriate conditions. These include high light intensity, high sodium chloride concentration, nitrate deficiency and extreme temperatures. Under these conditions, only D. salina and D. bardawil can accumulate â-carotene to as much as 10% of the cellular dry weight. Because the morphological characterization is based on the environmental factors, the Dunaliella will change the shape, so identification and differentiation of Dunaliella species by morphology is very difficult. In this research study, we isolated, identified and discriminated the different Dunaliella β-carotene producing strains from salt soil samples, by using 18S rDNA and internal transcribed spacer (ITS) gene sequences. The soil samples were collected from four different provinces of the North Eastern part of Thailand.namely: UdonThani, BuriRam, AmnartCharoen and Chaiyaphum. Among the four isolates, only BuriRam KU01 and UdonThani KU01 were D. salina and D. bardawil, respectively whereas AmnartCharoen KU01 and Chaiyaphum KU01 were not these Dunaliella species. At 4 M NaCl, with deficiency of nitrate (KNO3) and phosphate (KH2PO4) in the medium, the D. salina strain BuriRam KU01 produced β-carotene at the level of 56.25 ± 0.97 pg·cell-1 and D. bardawil strain UdonThani KU01 produced β-carotene at the level of 52.91 ± 0.29 pg·cell-1 at the 25th day after inoculation. The 18S rDNA and ITS sequences of D. salina strain BuriRam KU01 and D. bardawil strain UdonThani KU01 were submitted to the National Center for Biotechnology Information (NCBI) database with accession numbers of JN052202, JN052203, JN034031 and JN052204, respectively. By using the species-specific primers and ITS primers the â-carotene producing strains of Dunaliella was identified.Key words: 18S rDNA, β-carotene, carotenoid, Dunaliella bardawil, Dunaliella salina, internal transcribed spacer (ITS), salinity

Salt stress induced ion accumulation, ion homeostasis, membrane injury and sugar contents in salt-sensitive rice (Oryza sativa L. spp. indica) roots under isoosmotic conditions

Excess salt induced ionic and osmotic stresses that disturbed metabolism and led to reduction of plant development. Previous studies reported that sugars in stressed plants were involved in stress tolerance. However, the role of sugars in salt-stressed plants against only ionic effects is still unclear. The objective of this research was to investigate accumulation and homeostasis of ions, membrane injury, water content, growth characters and sugar contents in roots, in-response to salt stress under iso-osmotic conditions. Salt-sensitive rice, Pathumthani1 (PT1) was grown on MS culture medium for 7 days and was adjusted to salt stress under iso-osmotic conditions (-1.75 ± 0.20 MPa) by mannitol for 4 days. An increase in NaCl increased Na+ and Na+:K+ in PT1 roots leading to increased membrane injury, while the water content was decreased. Additionally, growth characters, including number, length, fresh weight and dry weight of roots, were inhibited. Sugar accumulations in PT1 roots were enhanced by increases in NaCl. The increase in Na+ was positively related to total soluble sugars, resulting in an osmotic adjustment of the membrane that maintained water availability. The accumulation of sugars in PT1 roots may be a primary salt-defense mechanism and may function as an osmotic control.Key words: Mannitol, membrane injury, oligosaccharides, sodium ion, potassium ion, sodium chloride

Submergence and Waterlogging Stress in Plants: A Review Highlighting Research Opportunities and Understudied Aspects

Soil flooding creates composite and complex stress in plants known as either submergence or waterlogging stress depending on the depth of the water table. In nature, these stresses are important factors dictating the species composition of the ecosystem. On agricultural land, they cause economic damage associated with long-term social consequences. The understanding of the plant molecular responses to these two stresses has benefited from research studying individual components of the stress, in particular low-oxygen stress. To a lesser extent, other associated stresses and plant responses have been incorporated into the molecular framework, such as ion and ROS signaling, pathogen susceptibility, and organ-specific expression and development. In this review, we aim to highlight known or suspected components of submergence/waterlogging stress that have not yet been thoroughly studied at the molecular level in this context, such as miRNA and retrotransposon expression, the influence of light/dark cycles, protein isoforms, root architecture, sugar sensing and signaling, post-stress molecular events, heavy-metal and salinity stress, and mRNA dynamics (splicing, sequestering, and ribosome loading). Finally, we explore biotechnological strategies that have applied this molecular knowledge to develop cultivars resistant to flooding or to offer alternative uses of flooding-prone soils, like bioethanol and biomass production

Effects of light intensity and the remaining nitrate concentration on the beta-carotene accumulation of a wild Dunaliella salina strain isolated from the saline soil

An isolated Dunaliella salina strain from northern Thailand was cultured in modified Johnson’s medium in column photobioreactor. The beta-carotene accumulation mainly depended on the quantities of cells entering into carotenogenesis condition that was significantly enhanced by high started KNO3 concentration. Low remaining nitrate concentration in the culture of each cell (RNCC) was suitable for algae to accumulate beta-carotene. Following the cultivation time extended, RNCC of all cultures decreased and tended to the same level (10-20 pg/cell) although the biomass or betacarotene content in the culture was higher in high started KNO3 concentration. High light intensity restrained the growth especially in low KNO3 concentration but improved betacarotene accumulation and RNCC. The highest biomass and beta-carotene dry weight (DW) were 2.25 g L-1 and 79.2 mg g-1 DW respectively. Above results indicated that increasing the biomass and as early as possible to strengthen the stress on each cell was important to improve the final beta-carotene yield

Short-term physiological responses to drought stress in seedling of tropical and temperate maize (Zea mays L.) cultivars

Understanding of the response of tropical and temperate maize (Zea mays L.) to drought is the first step for tolerant temperate maize improvement. Eight maize hybrids were used to investigate physiology responses under drought stress, four of them were tropical maize and the others were temperate maize. Results showed that there were different drought tolerances but similar trends in both tropical maize and temperate maize. Gas exchange parameters revealed different strategies of maize under the stress. In our study, most of the temperate hybrids maintained open stomata to keep a higher photosynthesis rate at the beginning of stress, while the other hybrids decreased stomatal conductance. Compared to temperate maize, the tropical maize had higher antioxidase activity and greater physiological parameter variation among hybrids. KS5731 and ZD309 had stronger drought resistance among tropical and temperate maize hybrids separately. Tolerant hybrids maintained active photosynthesis, have higher osmotic adjustment ability and antioxidase activities but lower malonaldehyde content than the sensitive ones. Our results led to a better understanding of the physiological responses of tropical and temperate maize plants to drought stress and may provide an insight of breeding for drought resistance in maize

Regulation of Translation by TOR, eIF4E and eIF2 alpha in Plants:Current Knowledge, Challenges and Future Perspectives

An important step in eukaryotic gene expression is the synthesis of proteins from mRNA, a process classically divided into three stages, initiation, elongation, and termination. Translation is a precisely regulated and conserved process in eukaryotes. The presence of plant-specific translation initiation factors and the lack of well-known translational regulatory pathways in this kingdom nonetheless indicate how a globally conserved process can diversify among organisms. The control of protein translation is a central aspect of plant development and adaptation to environmental stress, but the mechanisms are still poorly understood. Here we discuss current knowledge of the principal mechanisms that regulate translation initiation in plants, with special attention to the singularities of this eukaryotic kingdom. In addition, we highlight the major recent breakthroughs in the field and the main challenges to address in the coming years

The cyclin‐dependent kinase G group defines a thermo‐sensitive alternative splicing circuit modulating the expression of Arabidopsis ATU2AF65A

The ability to adapt growth and development to temperature variations is crucial to generate plant varieties resilient to predicted temperature changes. However, the mechanisms underlying plant response to progressive increases in temperature have just started to be elucidated. Here, we report that the Cyclin?dependent Kinase G1 (CDKG1) is a central element in a thermo?sensitive mRNA splicing cascade that transduces changes in ambient temperature into differential expression of the fundamental spliceosome component, ATU2AF65A. CDKG1 is alternatively spliced in a temperature?dependent manner. We found that this process is partly dependent on both the Cyclin?dependent Kinase G2 (CDKG2) and the interacting co?factor CYCLIN L1 resulting in two distinct messenger RNAs. Relative abundance of both CDKG1 transcripts correlates with ambient temperature and possibly with different expression levels of the associated protein isoforms. Both CDKG1 alternative transcripts are necessary to fully complement the expression of ATU2AF65A across the temperature range. Our data support a previously unidentified temperature?dependent mechanism based on the alternative splicing of CDKG1 and regulated by CDKG2 and CYCLIN L1. We propose that changes in ambient temperature affect the relative abundance of CDKG1 transcripts and this in turn translates into differential CDKG1 protein expression coordinating the alternative splicing of ATU2AF65AauthorsversionPeer reviewe

Relevance of the Axis Spermidine/eIF5A for Plant Growth and Development

One key role of the essential polyamine spermidine in eukaryotes is to provide the 4-aminobutyl moiety group destined to the post-translational modification of a lysine in the highly conserved translation factor eIF5A. This modification is catalyzed by two sequential enzymatic steps leading to the activation of eIF5A by the conversion of one conserved lysine to the unusual amino acid hypusine. The active translation factor facilitates the sequence-specific translation of polyproline sequences that otherwise cause ribosome stalling. In spite of the well-characterized involvement of active eIF5A in the translation of proline repeat-rich proteins, its biological role has been recently elucidated only in mammals, and it is poorly described at the functional level in plants. Here we describe the alterations in plant growth and development caused by RNAi-mediated conditional genetic inactivation of the hypusination pathway in Arabidopsis thaliana by knocking-down the enzyme deoxyhypusine synthase. We have uncovered that spermidine-mediated activation of elF5A by hypusination is involved in several aspects of plant biology such as the control of flowering time, the aerial and root architecture, and root hair growth. In addition this pathway is required for adaptation to challenging growth conditions such as high salt and high glucose medium and to elevated concentrations of the plant hormone ABA. We have also performed a bioinformatic analysis of polyproline-rich containing proteins as putative eIF5A targets to uncover their organization in clusters of protein networks to find molecular culprits for the disclosed phenotypes. This study represents a first attempt to provide a holistic view of the biological relevance of the spermidine-dependent hypusination pathway for plant growth and development.We thank Susana Tarraga from the Proteomics Service and Javier Forment from the Bioinformatics Service, both at the Instituto de Biologia Molecular y Celular de Plantas, for their technical assistance and to Jaideep Mathur (University of Guelph) for help with the confocal microscope images. We want to acknowledge Jose Leon for providing ft-10 seeds, and to R. Mirmira for sending us aliquots of the anti-hypusine antibody prior to its commercialization. Special thanks to CSIRO, MPG (Max-Planck-Gesellschaft zur Forderung der Wissenschaften) and Dr. Ian Moore (University of Oxford) for providing the binary plasmid pOpOff2. We acknowledge funding from the Spanish MICINN/MINECO (BIO2009-11818 and BIO2011-23828). BB was a recipient of a VALi+d predoctoral (ACIF2010/085) contract of the Generalitat Valenciana.Belda Palazón, B.; Almendáriz, C.; Martí Sanchis, E.; Carbonell Gisbert, J.; Ferrando Monleón, AR. (2016). Relevance of the Axis Spermidine/eIF5A for Plant Growth and Development. Frontiers in Plant Science. 7(245):1-14. https://doi.org/10.3389/fpls.2016.00245S114724