Exogenous expression of ACC deaminase gene in psychrotolerant bacteria alleviates chilling stress and promotes plant growth in millets under chilling conditions

463-468Endogeneous ethylene evolved during cold stress is a major limiting factor for plant growth which can be controlled by bacterial enzyme 1-aminocyclopropane-1-carboxylate (ACC) deaminase (ACCD), by breaking down ACC, the precursor of ethylene. In the present study, we introduced ACCD expressing plasmid in ACCD negative psychrotolerant bacteria to study its effect on growth of finger and foxtail millet seedlings. ACCD negative Sphingomonas faeni ISO were selected and transformed with plasmid pRKACC containing the acdS gene. Inoculation of the millet seeds and studying physiological parameters when a cold stress of 4 and 10ºC was imposed showed that inoculation with ACCD expressing strains improved root and shoot length, biomass content of foxtail and finger millets seeds. Further, we also observed increased antioxidant activity in the plants by high levels of SOD, CAT, GPX, POD, APX and GR enzyme activity, and decreased proline content on inoculation with ACCD positive mutants. The enzyme ACC deaminase is thus be proved to be a potential strategy to alleviate cold stress in foxtail and finger millet by regulating endogenous ethylene evolved during stress conditions

Complete mitochondrial genome sequence of a xerophilic fungus, Aspergillus pseudoglaucus

Aspergillus pseudoglaucus is a xerophilic filamentous fungus which can produce various secondary metabolites. Here, we reported the complete mitochondrial genome sequence of A. pseudoglaucus isolated from Meju, a soybean brick in Korea. Its mitochondrial genome was successfully assembled from raw reads sequenced using MiSeq by Velvet and SOAPGapCloser. Total length of the mitochondrial genome is 53,882 bp, which is third longest among known Aspergillus mitochondrial genomes and encoded 58 genes (30 protein-coding genes including hypothetical ORFs, two rRNAs, and 26 tRNAs). Nucleotide sequence of coding regions takes over 66.6% and overall GC content is 27.8%. Phylogenetic trees present that A. pseudoglaucus is located outside of section Nidulantes. Additional researches will be required for clarifying phylogenetic position of section Aspergillus

Cold Stress Tolerance in Psychrotolerant Soil Bacteria and Their Conferred Chilling Resistance in Tomato (<i>Solanum lycopersicum</i> Mill.) under Low Temperatures

<div><p>The present work aimed to study the culturable diversity of psychrotolerant bacteria persistent in soil under overwintering conditions, evaluate their ability to sustain plant growth and alleviate chilling stress in tomato. Psychrotolerant bacteria were isolated from agricultural field soil samples colleced during winter and then used to study chilling stress alleviation in tomato plants (<i>Solanum lycopersicum</i> cv Mill). Selective isolation after enrichment at 5°C yielded 40 bacterial isolates. Phylogenetic studies indicated their distribution in genera <i>Arthrobacter</i>, <i>Flavimonas</i>, <i>Flavobacterium</i>, <i>Massilia</i>, <i>Pedobacter</i> and <i>Pseudomonas</i>. Strains OS211, OB146, OB155 and OS261 consistently improved germination and plant growth when a chilling stress of 15°C was imposed and therefore were selected for pot experiments. Tomato plants treated with the selected four isolates exhibited significant tolerance to chilling as observed through reduction in membrane damage and activation of antioxidant enzymes along with proline synthesis in the leaves when exposed to chilling temperature conditions (15°C). Psychrotolerant physiology of the isolated bacteria combined with their ability to improve germination, plant growth and induce antioxidant capacity in tomato plants can be employed to protect plants against chilling stress.</p></div

Plant growth promoting characteristics of the isolates analyzed at 5°C.

<p>Plant growth promoting characteristics of the isolates analyzed at 5°C.</p

Psychrotolerant characteristics of the isolates as observed by days taken for colony appearance at 5 and 25°C and maximum temperatures of growth.

<p>Psychrotolerant characteristics of the isolates as observed by days taken for colony appearance at 5 and 25°C and maximum temperatures of growth.</p

Heat map indicating the distribution of cellular fatty acids taken as markers for cold adaptation.

<p>Pair-wise Pearson correlation coefficients were used to generate heat map using MultiExperiment Viewer (MeV) software v 4.9.0. Color scale is representative of the percentage of fatty acids.</p

Physiochemical properties of the collected soil samples.

<p>Physiochemical properties of the collected soil samples.</p

Phylogenetic diversity among the psychrotolerant bacterial isolates.

<p>Neighbor-joining tree was constructed based on 16S rRNA gene sequences. GenBank accession numbers of individual member strains are given in parentheses. Scale bar corresponds to 0.05 units of the number of base substitutions per site.</p

Re-Identification of <i>Aspergillus</i> Subgenus <i>Nidulantes</i> Strains and Description of Three Unrecorded Species From Korea

Aspergillus subgenus Nidulantes with nine section forms the second largest subgenus of the fungi that comes under the genus Aspergillus. Species in this group of fungi are important as they are reported to play several important roles in the environment including influencing air quality in confined spaces, food spoilage, production of mycotoxins as well as in human pathogenicity. In the present study, 53 strains of Aspergillus subgenus Nidulantes (section: Nidulantes & Usti) isolated from Korea and preserved at the Korean Agricultural Culture Collection (KACC) were subjected to re-identification by using a combined dataset of partial β-tubulin (BenA), Calmodulin (CaM) gene sequences as well as their morphological data. We confirmed 14 species from 53 isolates in Korea. Of them, eleven species were reported in Korea previously (A. amoenus, A. baeticus, A. calidoustus, A. creber, A. insuetus, A. jensenii, A. nidulans, A. protuberus, A. sydowii, A. tabacinus and A. unguis), and three species (A. griseoaurantiacus, A. puulaauensis and A. sublatus) were previously unreported from Korea. We detailed the characteristic features of these three species, that remain unexplored in Korea.</p

Lipid ROS- and Iron-Dependent Ferroptotic Cell Death in Unicellular Algae Chlamydomonas reinhardtii

The phenomenon of heat stress leading to ferroptosis-like cell death has recently been observed in bacteria as well as plant cells. Despite recent findings, the evidence of ferroptosis, an iron-dependent cell death remains unknown in microalgae. The present study aimed to investigate if heat shock could induce reactive oxygen species (ROS) and iron-dependent ferroptotic cell death in Chlamydomonas reinhardtii in comparison with RSL3-induced ferroptosis. After RSL3 and heat shock (50 &deg;C) treatments with or without inhibitors, Chlamydomonas cells were evaluated for cell viability and the induction of ferroptotic biomarkers. Both the heat shock and RSL3 treatment were found to trigger ferroptotic cell death, with hallmarks of glutathione&ndash;ascorbic acid depletion, GPX5 downregulation, mitochondrial dysfunction, an increase in cytosolic calcium, ROS production, lipid peroxidation, and intracellular iron accumulation via heme oxygenase-1 activation (HO-1). Interestingly, the cells preincubated with ferroptosis inhibitors (ferrostatin-1 and ciclopirox) significantly reduced RSL3- and heat-induced cell death by preventing the accumulation of Fe2+ and lipid ROS. These findings reveal that ferroptotic cell death affects the iron homeostasis and lipid peroxidation metabolism of Chlamydomonas, indicating that cell death pathways are evolutionarily conserved among eukaryotes