Overexpression of alfalfa mitochondrial HSP23 in prokaryotic and eukaryotic model systems confers enhanced tolerance to salinity and arsenic stress

The cloning and characterization of a gene (MsHSP23) coding for a heat shock protein in alfalfa in a prokaryotic and model plant system is described. MsHSP23 contains a 633 bp ORF encoding a polypeptide of 213 amino acids and exhibits greater sequence similarity to mitochondrial sHSPs from dicotyledons than to those from monocotyledons. When expressed in bacteria, recombinant MsHSP23 conferred tolerance to salinity and arsenic stress. Furthermore, MsHSP23 was cloned in a plant expressing vector and transformed into tobacco, a eukaryotic model organism. The transgenic plants exhibited enhanced tolerance to salinity and arsenic stress under ex vitro conditions. In comparison to wild type plants, the transgenic plants exhibited significantly lower electrolyte leakage. Moreover, the transgenic plants had superior germination rates when placed on medium containing arsenic. Taken together, these overexpression results imply that MsHSP23 plays an important role in salinity and arsenic stress tolerance in transgenic tobacco. This approach could be useful to develop stress tolerant crops including forage crops

Overexpression of arabidopsis YUCCA6 in potato results in high-auxin developmental phenotypes and enhance

Indole-3-acetic acid (IAA), a major plant auxin, is produced in both tryptophan-dependent and tryptophanindependent pathways. A major pathway in Arabidopsis thaliana generates IAA in two reactions from tryptophan. Step one converts tryptophan to indole-3-pyruvic acid (IPA) by tryptophan aminotransferases followed by a rate-limiting step converting IPA to IAA catalyzed by YUCCA proteins. We identified eight putative StYUC (Solanum tuberosum YUCCA) genes whose deduced amino acid sequences share 50%-70% identity with those of Arabidopsis YUCCA proteins. All include canonical, conserved YUCCA sequences: FATGY motif, FMO signature sequence, and FAD-binding and NADPbinding sequences. In addition, five genes were found with ~50% amino acid sequence identity to Arabidopsis tryptophan aminotransferases. Transgenic potato (Solanum tuberosum cv. Jowon) constitutively overexpressing Arabidopsis AtYUC6 displayed high-auxin phenotypes such as narrow downward-curled leaves, increased height, erect stature, and longevity. Transgenic potato plants overexpressing AtYUC6 showed enhanced drought tolerance based on reduced water loss. The phenotype was correlated with reduced levels of reactive oxygen species in leaves. The results suggest a functional YUCCA pathway of auxin biosynthesis in potato that may be exploited to alter plant responses to the environment. © 2012 The Author

Release of SOS2 kinase from sequestration with GIGANTEA determines salt tolerance in Arabidopsis

Kim, Woe-Yeon et al.--Environmental challenges to plants typically entail retardation of vegetative growth and delay or cessation of flowering. Here we report a link between the flowering time regulator, GIGANTEA (GI), and adaptation to salt stress that is mechanistically based on GI degradation under saline conditions, thus retarding flowering. GI, a switch in photoperiodicity and circadian clock control, and the SNF1-related protein kinase SOS2 functionally interact. In the absence of stress, the GI:SOS2 complex prevents SOS2- based activation of SOS1, the major plant Na+/H+-antiporter mediating adaptation to salinity. GI over-expressing, rapidly flowering, plants show enhanced salt sensitivity, whereas gi mutants exhibit enhanced salt tolerance and delayed flowering. Salt-induced degradation of GI confers salt tolerance by the release of the SOS2 kinase. The GISOS2 interaction introduces a higher order regulatory circuit that can explain in molecular terms, the long observed connection between floral transition and adaptive environmental stress tolerance in Arabidopsis.This research was supported by the Next-Generation BioGreen 21 Program (Systems and Synthetic Agrobiotech Center, no. PJ008025), a Cooperative Research Program for Agriculture Science & Technology Development (Project No. PJ007850), and the Ministry of Education, Science and Technology for the World Class University (WCU) program (R32-10148) from the Rural Development Administration, Republic of Korea, and by grant BIO2009-08641 financed by the Spanish Ministry of Science and Innovation and the FEDER program.Peer reviewe

A novel thiol-reductase activity of Arabidopsis YUC6 confers drought tolerance independently of auxin biosynthesis

13 páginas.-- 7 figuras.-- 69 referencias.-- Supplementary Information: Supplementary Figures 1-7 and Supplementary Tables 1-2YUCCA (YUC) proteins constitute a family of flavin monooxygenases (FMOs), with an important role in auxin (IAA) biosynthesis. Here we report that Arabidopsis plants overexpressing YUC6 display enhanced IAA-related phenotypes and exhibit improved drought stress tolerance, low rate of water loss and controlled ROS accumulation under drought and oxidative stresses. Co-overexpression of an IAA-conjugating enzyme reduces IAA levels but drought stress tolerance is unaffected, indicating that the stress-related phenotype is not based on IAA overproduction. YUC6 contains a previously unrecognized FAD- and NADPH-dependent thiol-reductase activity (TR) that overlaps with the FMO domain involved in IAA biosynthesis. Mutation of a conserved cysteine residue (Cys-85) preserves FMO but suppresses TR activity and stress tolerance, whereas mutating the FAD- and NADPH-binding sites, that are common to TR and FMO domains, abolishes all outputs. We provide a paradigm for a single protein playing a dual role, regulating plant development and conveying stress defence responses.We thank Dr Yunde Zhao for generously sharing the quadruple mutant yuc1,2,4,6 seeds and Dr Verena Kriechbaumer for kindly supporting comments for in vitro YUC assay. This work was supported by grants from the National Research Foundation of Korea (NRF) funded by the Korean Government (MSIP; 2013R1A2A1A01005170) and Next-Generation BioGreen21 Program (SSAC, PJ01106901), Rural Development Administration, Republic of Korea. J.-Y.C. and M.R.K. were supported by a scholarship from the BK21Plus Program, the Ministry of Education, Korea. M.N. and T.A. were supported by grants from Core Research for Evolutional Science and Technology (CREST) of Japan Science and Technology Agency (JST), JapanPeer reviewe

Electrophysiological modelling of pulmonary artery smooth muscle cells in the rabbits--special consideration to the generation of hypoxic pulmonary vasoconstriction

In vascular smooth muscle cells, it has been suggested that membrane potential is an important component that initiates contraction. We developed a mathematical model to elucidate the quantitative contributions of major ion currents [a voltage-gated L-type Ca2+ current (ICaL), a voltage-sensitive K+ current (IKV), a Ca2+-activated K+ current (IKCa) and a nonselective cation current (INSC)] to membrane potential. In order to typify the diverse nature of pulmonary artery smooth muscle cells (PASMCs), we introduced parameters that are not fixed (variable parameters). The population of cells with different parameters was constructed and the cells that have the electrophysiological properties of PASMCs were selected. The contributions of each membrane current were investigated by sensitivity analysis and modification of the current parameters. Consequently, IKV and INSC were found to be the most important currents that affect the membrane potential. The occurrence of depolarisation in hypoxic pulmonary vasoconstriction (HPV) was also examined. In hypoxia, IKV and IKCa were reduced, but the consequent depolarisation in simulation was not enough to initiate contractions. If we add an increase of INSC (2.5-fold), the calculated membrane potential was enough to induce contraction. From the results, we conclude that the balance of various ion channel activities determines the resting membrane potential of PASMCs and our model was successful in explaining the depolarisation in HPV. Therefore, this model can be a powerful tool to investigate the various electrical properties of PASMCs in both normal and pathological conditions

Ethylene enhances transcriptions of asparagine biosynthetic genes in soybean (Glycine max L. Merr) leaves

Soybean, a vital protein-rich crop, offers bioactivity that can mitigate various chronic human diseases. Nonetheless, soybean breeding poses a challenge due to the negative correlation between enhanced protein levels and overall productivity. Our previous studies demonstrated that applying gaseous phytohormone, ethylene, to soybean leaves significantly boosts the accumulation of free amino acids, particularly asparagine (Asn). Current studies also revealed that ethylene application to soybeans significantly enhanced both essential and non-essential amino acid contents in leaves and stems. Asn plays a crucial role in ammonia detoxification and reducing fatigue. However, the molecular evidence supporting this phenomenon remains elusive. This study explores the molecular mechanisms behind enhanced Asn accumulation in ethylene-treated soybean leaves. Transcriptional analysis revealed that ethylene treatments to soybean leaves enhance the transcriptional levels of key genes involved in Asn biosynthesis, such as aspartate aminotransferase (AspAT) and Asn synthetase (ASN), which aligns with our previous observations of elevated Asn levels. These findings shed light on the role of ethylene in upregulating Asn biosynthetic genes, subsequently enhancing Asn concentrations. This molecular insight into amino acid metabolism regulation provides valuable knowledge for the metabolic farming of crops, especially in elevating nutraceutical ingredients with non-genetic modification (GM) approach for improved protein content

GIGANTEA is a co-chaperone which facilitates maturation of ZEITLUPE in the Arabidopsis circadian clock

Circadian clock systems help establish the correct daily phasing of the behavioral, developmental, and molecular events needed for the proper coordination of physiology and metabolism. The circadian oscillator comprises transcription-translation feedback loops but also requires post-translational processes that regulate clock protein homeostasis. GIGANTEA is a unique plant protein involved in the maintenance and control of numerous facets of plant physiology and development. Through an unknown mechanism GIGANTEA stabilizes the F-box protein ZEITLUPE, a key regulator of the circadian clock. Here, we show that GIGANTEA has general protein chaperone activity and can act to specifically facilitate ZEITLUPE maturation into an active form in vitro and in planta. GIGANTEA forms a ternary complex with HSP90 and ZEITLUPE and its co-chaperone action synergistically enhances HSP90/HSP70 maturation of ZEITLUPE in vitro. These results identify a molecular mechanism for GIGANTEA activity that can explain its wide-ranging role in plant biology

Whole-exome sequencing identified a missense mutation in WFS1 causing low-frequency hearing loss: a case report

Abstract Background Low-frequency nonsyndromic hearing loss (LF-NSHL) is a rare, inherited disorder. Here, we report a family with LF-NSHL in whom a missense mutation was found in the Wolfram syndrome 1 (WFS1) gene. Case presentation Family members underwent audiological and imaging evaluations, including pure tone audiometry and temporal bone computed tomography. Blood samples were collected from two affected and two unaffected subjects. To determine the genetic background of hearing loss in this family, genetic analysis was performed using whole-exome sequencing. Among 553 missense variants, c.2419A → C (p.Ser807Arg) in WFS1 remained after filtering and inspection of whole-exome sequencing data. This missense mutation segregated with affected status and demonstrated an alteration to an evolutionarily conserved amino acid residue. Audiological evaluation of the affected subjects revealed nonprogressive LF-NSHL, with early onset at 10 years of age, but not to a profound level. Conclusion This is the second report to describe a pathological mutation in WFS1 among Korean patients and the second to describe the mutation in a different ethnic background. Given that the mutation was found in independent families, p.S807R possibly appears to be a “hot spot” in WFS1, which is associated with LF-NSHL