<Emphasis Type="Italic">Nibribacter flagellatus</Emphasis> sp. nov., isolated from rhizosphere of <Emphasis Type="Italic">Hibiscus syriacus</Emphasis> and emended description of the genus <Emphasis Type="Italic">Nibribacter</Emphasis>

A Gram-stain negative, aerobic, motile by flagella, rod-shaped strain (THG-T16^T) was isolated from rhizosphere of Hibiscus syriacus. Growth occurred at 10–40 °C (optimum 28–30 °C), at pH 6.0–8.0 (optimum 7.0) and at 0–1.0% NaCl (optimum 0%). Based on 16S rRNA gene sequence analysis, the near phylogenetic neighbours of strain THG-T16^T were identified as Nibribacter koreensis KACC 16450^T (98.6%), Rufibacter roseus KCTC 42217^T (94.7%), Rufibacter immobilis CCTCC AB 2013351^T (94.5%) and Rufibacter tibetensis CCTCC AB 208084^T (94.4%). The DNA G+C content of strain THG-T16^T was determined to be 46.7 mol%. DNA–DNA hybridization values between strain THG-T16^T and N. koreensis KACC 16450^T, R. roseus KCTC 42217^T, R. immobilis CCTCC AB 2013351^T, R.tibetensis CCTCC AB 208084^T were 33.5?±?0.5% (31.7?±?0.7% reciprocal analysis), 28.1?±?0.2% (25.2?±?0.2%), 17.1?±?0.9% (10.2?±?0.6%) and 8.1?±?0.3% (5.2?±?0.1%). The polar lipids were identified as phosphatidylethanolamine, two unidentified aminophospholipids, an unidentified aminolipid and three unidentified lipids. The quinone was identified as MK-7 and the polyamine as sym-homospermidine. The major fatty acids were identified as C_16:1 ω5c, C_17:1 ω6c, iso-C_15:0, summed feature 3 (C_16:1 ω7c and/or C_16:1 ω6c) and summed feature 4 (iso-C_17:1 I and/or anteiso-C_17:1 B). On the basis of the phylogenetic analysis, chemotaxonomic data, physiological characteristics, and DNA–DNA hybridization data, strain THG-T16^T represents a novel species of the genus Nibribacter, for which the name Nibribacter flagellatus sp. nov. is proposed. The type strain is THG-T16^T(=?KACC 19188^T?=?CCTCC AB 2016246^T).     

The aromatic cytokinin <Emphasis Type="Italic">meta-</Emphasis>topolin promotes in vitro propagation,shoot quality and micrografting in <Emphasis Type="Italic">Corylus colurna</Emphasis> L.

The role of 4.1 or 8.2 μM meta-topolin (mT) on shoot multiplication, rooting and ex vitro acclimatization of micropropagated Corylus colurna L., a promising non-suckering rootstock for hazelnut (Corylus avellana L.), was examined in comparison to N⁶-benzyladenine (BA), the most used cytokinin in tissue culture of Corylus spp. The influence of 8.2 μM mT and BA on photosynthetic pigments content and antioxidant enzymes activity, catalase (CAT) and guaiacol peroxidase (POD), in regenerated shoots, and on the preparation of the rootstock for micrografting was also evaluated. The highest shoot multiplication was recorded on medium containing 8.2 μM mT and an overall positive effect of mT on growth and quality of micropropagated shoots was found. The highest chlorophyll a content (1.236 mg g^?1 fresh weight, FW) and chlorophyll a/b ratio (2.48), and the lowest total carotenoids content (0.292 mg g^?1 FW) and CAT activity (25.8 μmol min^?1 mg^?1 protein) were detected after 8.2 μM mT application, while no significant differences were found in chlorophyll b content and POD activity between the two cytokinins. The best rhizogenesis response (98% for 4.1 μM and 100% for 8.2 μM mT) and ex vitro acclimatization competence (higher than 78%) were exhibited from shoots multiplied on mT. Furthermore, the multiplication of rootstock on mT allowed obtaining the highest (70%) response of successful micrografting. The present findings provide the first evidence of the successful applicability of mT in C. colurna tissue culture and development of micrografted plantlets.     

Iron homeostasis in tropical <Emphasis Type="Italic">indica</Emphasis> rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.) cultivars having contrasting grain iron concentration

Iron homeostasis was studied in two tropical indica rice cultivars viz. Sharbati (high Fe) and Lalat (low Fe) having contrasting grain Fe concentration. Plants were hydroponically grown with 5 concentrations of Fe (0.05, 2, 5, 15, 50 mg L^?1) till maturity. The effect of incremental Fe treatment on the plant was followed by analyzing accumulation of ferritin protein, activities of aconitase enzyme, enzymes of anti-oxidative defense and accumulation of hydrogen peroxide and ascorbic acid. Plant growth was adversely affected beyond 15 mg L^?1 of Fe supplementation and effects of Fe stress (both deficiency and excess) were more apparent on the high Fe containing cultivar Sharbati than the low Fe containing Lalat. Level of ferritin protein and aconitase activity increased up to 5 mg L^?1 of Fe concentration. Lalat continued to synthesize ferritin protein at much higher Fe level than Sharbati and the cultivar also had higher activities of peroxidase, superoxide dismutase and glutathione reductase. It was concluded that the tolerance of Lalat to Fe stress was because of its higher intrinsic ability to scavenge free radicals of oxidative stress for possessing higher activity of antioxidative enzymes. This, together with its capacity to sequester the excess Fe in ferritin protein over a wider range of Fe concentrations made it more tolerant to Fe stress.     

Production of <Emphasis Type="Italic">trans</Emphasis>-10,<Emphasis Type="Italic">cis</Emphasis>-12-conjugated linoleic acid using permeabilized whole-cell biocatalyst of <Emphasis Type="Italic">Yarrowia lipolytica</Emphasis>

Objective

To improve the production of trans-10,cis-12-conjugated linoleic acid (t10,c12-CLA) from linoleic acid in recombinant Yarrowia lipolytica.

Results

Cells of the yeast were permeabilized by freeze/thawing. The optimal conditions for t10,c12-CLA production by the permeabilized cells were at 28 °C, pH 7, 200 rpm with 1.5 g sodium acetate l^?1, 100 g wet cells l^?1, and 25 g LA l^?1. Under these conditions, the permeabilized cells produced 15.6 g t10,c12-CLA l^?1 after 40 h, with a conversion yield of 62 %. The permeabilized cells could be used repeatedly for three cycles, with the t10,c12-CLA extracellular production remaining above 10 g l^?1.

Conclusion

Synthesis of t10,c12-CLA was achieved using a novel method, and the production reported in this work is the highest value reported to date.

     

Accumulation and tolerance characteristics of lead in <Emphasis Type="Italic">Althaea rosea</Emphasis> Cav. and <Emphasis Type="Italic">Malva crispa</Emphasis> L.

Two ornamental plants of Althaea rosea Cav. and Malva crispa L. were exposed to various concentrations of lead (Pb) (0, 50, 100, 200 and 500 mg·kg^?1) for 70 days to evaluate the accumulating potential and the tolerance characteristics. The results showed that both plant species grown normally under Pb stress, and A. rosea had a higher tolerance than M. crispa, while M. crispa had a higher ability in Pb accumulation than A. rosea. Besides, lower Pb concentration (50 mg·kg^?1) stimulated the shoot biomass in both plant species. Pb accumulation in plants was consistent with the increase of Pb levels, and the main accumulation sites were the roots and the older leaves. In addition, the photosynthetic pigments content and chlorophyll fluorescence parameters were influenced by Pb stress. In such case, both of the plants could improve the activities of antioxidant enzymes of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX), and the contents of the total soluble sugar and soluble protein, which reached the highest value at Pb 100 mg·kg^?1, as well as the accumulation of the total thiols (T-SH) and non-protein thiols (NP-SH) to adapt to Pb stress. Thus, it provides the theoretical basis and possibility for ornamental plants of A. rosea and M. crispa in phytoremediation of Pb contaminated areas.     

Exogenous spermidine alleviates fruit granulation in a <Emphasis Type="Italic">Citrus</Emphasis> cultivar (<Emphasis Type="Italic">Huangguogan</Emphasis>) through the antioxidant pathway

The role of exogenous spermidine (Spd) in alleviating fruit granulation in the grafted seedlings of a Citrus cultivar (Huangguogan) was investigated. Granulation resulted in increased electrical conductivity, cell membrane permeability, and total pectin, soluble pectin, cellulose, and lignin contents. However, it decreased the activities of superoxide dismutase, peroxidase, and catalase, as well as the (Spd + Spm):Put ratio. The application of exogenous Spd onto Huangguogan seedlings significantly increased proline and ascorbate contents, but decreased the H₂O₂ and O ₂ ^?· levels, which suggested that exogenous Spd provided some protection from oxidative damage. In addition, exogenous Spd decreased cell membrane permeability and MDA content, and increased the (Spd + Spm):Put ratio. The activities of antioxidant enzymes, such as catalase, peroxidase, and superoxide dismutase, were increased in Spd-treated seedlings affected by fruit granulation, resulting in a decrease in oxidative stress levels. The protective effects of Spd were reflected by a decrease in superoxide levels through osmoregulation, increased proline and ascorbate contents, and increased antioxidant activities. Our observations reveal the importance of exogenous Spd in alleviating citrus fruit granulation.     

Endophytic <Emphasis Type="Italic">Alcaligenes</Emphasis> Isolated from Horticultural and Medicinal Crops Promotes Growth in Okra (<Emphasis Type="Italic">Abelmoschus</Emphasis><Emphasis Type="Italic">esculentus</Emphasis>)

The potential of endophytic bacteria to act as biofertilizers and bioprotectants has been demonstrated, and considerable progress has been made in explaining their role in plant protection. In the present study, three endophytic bacterial strains (BHU 12, BHU 16 isolated from the leaves of Abelmoschus esculentus, and BHU M7 isolated from the leaves of Andrographis paniculata) were used which displayed high sequence similarity to Alcaligenes faecalis. The biofilm formation ability of these endophytic strains in the presence of okra root exudates confirms their chemotactic ability, an initial step for successful endophytic colonization. Further, reinoculation of spontaneous rifampicin-tagged mutants into okra seedlings revealed a CFU count above 10⁵ cells g^?1 of all three endophytic strains in root samples during the first 15 days of plant growth. The CFU count increased up to 10¹³ by 30 days of plant growth, followed by a gradual decline to approximately 10¹⁰ cells g^?1 at 45 days of plant growth. Systemic endophytic colonization was further supported by 2, 3, 5-triphenyl tetrazolium chloride staining and fluorescence imaging of ds-RED expressing conjugants of the endophytic strains. The strains were further assessed for their plausible in vivo and in vitro plant growth-promoting and antagonistic abilities. Our results demonstrated that the endophytic strains BHU 12, BHU 16, and BHU M7 augmented plant biomass by greater than 40 %. Root and shoot lengths of okra plants when primed by BHU 12, BHU 16, and BHU M7 increased up to 34 and 14.5 %, respectively. The endophytic isolates also exhibited significant in vitro antagonistic potential against the collar rot pathogen Sclerotium rolfsii. In summary, our results demonstrate excellent potential of the three endophytic bacterial strains as biofertilizers and biocontrol agents, indicating the possibility for use in sustainable agriculture.     

<Emphasis Type="Italic">C7</Emphasis>-prenylation of tryptophanyl and <Emphasis Type="Italic">O</Emphasis>-prenylation of tyrosyl residues in dipeptides by an <Emphasis Type="Italic">Aspergillus terreus</Emphasis> prenyltransferase

During our search for novel prenyltransferases, a putative gene ATEG_04218 from Aspergillus terreus raised our attention and was therefore amplified from strain DSM 1958 and expressed in Escherichia coli. Biochemical investigations with the purified recombinant protein and different aromatic substrates in the presence of dimethylallyl diphosphate revealed the acceptance of all the tested tryptophan-containing cyclic dipeptides. Structure elucidation of the main enzyme products by NMR and MS analyses confirmed the attachment of the prenyl moiety to C-7 of the indole ring, proving the identification of a cyclic dipeptide C7-prenyltransferase (CdpC7PT). For some substrates, reversely C3- or N1-prenylated derivatives were identified as minor products. In comparison to the known tryptophan-containing cyclic dipeptide C7-prenyltransferase CTrpPT from Aspergillus oryzae, CdpC7PT showed a much higher substrate flexibility. It also accepted cyclo-l-Tyr-l-Tyr as substrate and catalyzed an O-prenylation at the tyrosyl residue, providing the first example from the dimethylallyltryptophan synthase (DMATS) superfamily with an O-prenyltransferase activity towards dipeptides. Furthermore, products with both C7-prenyl at tryptophanyl and O-prenyl at tyrosyl residue were detected in the reaction mixture of cyclo-l-Trp-l-Tyr. Determination of the kinetic parameters proved that (S)-benzodiazepinedione consisting of a tryptophanyl and an anthranilyl moiety was accepted as the best substrate with a K _M value of 204.1 μM and a turnover number of 0.125 s^?1. Cyclo-l-Tyr-l-Tyr was accepted with a K _M value of 1,411.3 μM and a turnover number of 0.012 s^?1.     

Glutathione improves survival of cryopreserved embryogenic calli of <Emphasis Type="Italic">Agapanthus praecox</Emphasis> subsp. <Emphasis Type="Italic">orientalis</Emphasis>

The effect of supplementation of reduced glutathione (GSH) to cryoprotectant solution on the generation of reactive oxygen species (ROS) (e.g., H₂O₂, OH^·, and O ₂ ^·? ) and antioxidants (e.g., SOD, POD, CAT, AsA, and GSH), as well as membrane lipid peroxidation (i.e., MDA content) mitigation in cryopreserving of embryogenic calli (EC) of Agapanthus praecox subsp. orientalis was investigated. The vitrification-based cryopreservation method was used in this study. The addition of GSH at a final concentration of 0.08 mM to the cryoprotectant solution has significantly improved cryotolerance of A. praecox EC. The EC post-thaw survival rate increased by 68.34 % using the cryoprotectant solution containing 0.08 mM GSH as compared to the control (GSH-free). EC treated with GSH displayed the reduction in  OH^· generation activity and the contents of H₂O₂ and MDA, as well as enhancement in the inhibition of O ₂ ^·? generation and the antioxidant activity. Treatment with exogenous GSH also increased endogenous AsA and GSH contents after dehydration step. Expression of stress-responsive genes, e.g., peroxidase (POD), peroxiredoxin, ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), and glutathione peroxidase (GPX), was also increased during cryopreservation processes. The expression of DAD1 (Defender against apoptotic cell death) was elevated, while cell death-related protease SBT was suppressed. These results demonstrated that the addition of GSH to cryoprotectant solution affects the ROS level and could effectively improve survival of A. praecox EC through enhancing antioxidant enzyme activities and decreasing cell death.     

Molecular cloning and functional analysis of <Emphasis Type="Italic">DoUGE</Emphasis> related to water-soluble polysaccharides from <Emphasis Type="Italic">Dendrobium officinale</Emphasis> with enhanced abiotic stress tolerance

UDP glucose 4-epimerase (UGE), an enzyme with significant impacts on sugar metabolism, catalyzes the reversible inter-conversion between UDP-glucose and UDP-galactose. However, very little is known about whether UGE plays a critical role in the accumulation of water-soluble polysaccharide (WSP) and its relationship to abiotic stress tolerance. Here, DoUGE from D. officinale, encoding UGE localized in the cytoplasm, was initially cloned and analyzed. DoUGE exhibited highly tissue-specific expression patterns. The highest expression was in the stems of seedlings and adult plants. The content of WSPs ranged from 168.43 to 416.12 mg g^?1 DW from developmental stages S1 to S4, the highest value being in S3. DoUGE was expressed throughout S1 to S4, with a maximum in S3. This trend was similar in three cultivated varieties (T10, T32-5 and T636). There was a positive correlation between DoUGE expression and the content of WSPs (R ² ?=?0.94; p?<?0.01). Furthermore, promoter analysis showed its possible role in responses to abiotic stresses. Transgenic Arabidopsis thaliana seedlings overexpressing DoUGE accumulated 34.84–44.78% more WSPs, showed 26.24–32.79% more UGE activity, and had a 1.19–1.31-fold higher chlorophyll content than the wild type. Transgenic plants also showed a 50.84 and 34.33% increase in the average content of glucose and galactose, respectively. Transgenic lines growing in half-strength Murashige and Skoog medium containing 150 mM NaCl or 200 mM mannitol displayed enhanced root length and fresh weight, as well as lower proline and malondialdehyde accumulation under salt and osmotic stresses, indicating that the DoUGE gene could be used to improve tolerance to abiotic stress in crops and medicinal or ornamental plants. Our results provide genetic evidence for the involvement of DoUGE in the regulation of WSP content during plant development in D. officinale, as well as in enhanced tolerance to salt and osmotic stresses.     

Improvement of seedling and panicle blast resistance in <Emphasis Type="Italic">Xian</Emphasis> rice varieties following <Emphasis Type="Italic">Pish</Emphasis> introgression

Rice blast is a serious disease caused by the filamentous ascomycetous fungus Magnaporthe oryzae. Incorporating disease resistance genes in rice varieties and characterizing the distribution of M. oryzae isolates form the foundation for enhancing rice blast resistance. In this study, the blast resistance gene Pish was observed to be differentially distributed in the genomes of rice sub-species. Specifically, Pish was present in 80.5% of Geng varieties, but in only 2.3% of Xian varieties. Moreover, Pish conferred resistance against only 23.5% of the M. oryzae isolates from the Geng-planting regions, but against up to 63.2% of the isolates from the Xian-planting regions. Thus, Pish may be an elite resistance gene for improving rice blast resistance in Xian varieties. Therefore, near-isogenic lines (NILs) with Pish and the polygene pyramid lines (PPLs) PPL^Pish/Pi1, PPL^Pish/Pi54, and PPL^Pish/Pi33 in the Xian background Yangdao 6 were generated using a molecular marker-assisted selection method. The results suggested that (1) Pish significantly improved rice blast resistance in Xian varieties, which exhibited considerably improved seedling and panicle blast resistance after Pish was introduced; (2) PPLs with Pish were more effective than the NILs with Pish regarding seedling and panicle blast resistance; (3) the PPL seedling and panicle blast resistance was improved by the complementary and overlapping effects of different resistance genes; and (4) the stability of NIL and PPL resistance varied under different environmental conditions, with only PPL^Pish/Pi54 exhibiting highly stable resistance in three natural disease nurseries (Jianyang, Jinggangshan, and Huangshan). This study provides new blast resistance germplasm resources and describes a novel molecular strategy for enhancing rice blast resistance.     

Growth and phosphorus removal by <Emphasis Type="Italic">Synechococcus elongatus</Emphasis> co-immobilized in alginate beads with <Emphasis Type="Italic">Azospirillum brasilense</Emphasis>

This study examined the co-immobilization of the cyanobacterium Synechococcus elongatus with the plant growth-promoting bacterium Azospirillum brasilense in alginate beads and its potential application for the removal of phosphorus from aquaculture wastewater. Co-immobilization of both microorganisms significantly increased the cell density of S. elongatus (2852.5?×?10⁴ cells mL^?1) compared with that of immobilization of cyanobacteria alone (1325.2?×?10⁴ cells mL^?1). Chlorophyll a content was similar in co-immobilized (11.1?±?3.5 pg cell^?1) and immobilized S. elongatus (14.5?±?4.9 pg cell^?1). Azospirillum brasilense showed continuous growth until day 2, after which its cell concentration declined until the end of the assay. Co-immobilized S. elongatus removed more phosphorus (44.8 %) than immobilized cyanobacteria cells alone (32.0 %). In conclusion, phosphate removal was greater with free cells of S. elongatus but overlapped with the values that were obtained with the treatment of co-immobilization of cells. Our results demonstrate that A. brasilense enhances the growth of S. elongatus and improves its removal of phosphorus when they are co-immobilized in alginate beads compared with only immobilization of cyanobacteria cells alone.     

Effect of over-expression of <Emphasis Type="Italic">Linum usitatissimum</Emphasis> PINORESINOL LARICIRESINOL REDUCTASE (<Emphasis Type="Italic">LuPLR</Emphasis>) gene in transgenic <Emphasis Type="Italic">Phyllanthus amarus</Emphasis>

Shoot tip explants of Phyllanthus amarus were cocultivated with Agrobacterium tumefaciens strain LBA 4404 carrying plasmid pCAMBIA 2301 harbouring genes coding for betaglucuronidase (gus), kanamycin (kan), and neomycin phosphotransferase II (nptII) along with a gene coding for Linum usitatissimum PINORESINOL LARICIRESINOL REDUCTASE (Lu-PLR). Transformed shoot tip explants were maintained in a Murashige and Skoog (MS) medium containing TDZ 1.54 mg l^?1, kan 50 mg l^?1 and cephotaxime 62.5 mg l^?1. The optimum medium for regeneration of multiple shoots was MS supplemented with TDZ 1.54 mg l^?1, kan 50 mg l^?1. Efficient and effective rooting of plantlets was achieved by culturing the in vitro regenerated shoots on liquid ½ MS medium containing 0.7 mg l^?1 indole 3-butyric acid (IBA) and 5 mg l^?1 kan. Rooted plants were acclimatized in the mixtures of vermiculite and soil. The transformation of kan-resistant plantlets regenerated from shoot-tip explants was confirmed by GUS and polymerase chain reaction (PCR) analysis. Southern blot and reverse transcribed PCR (RT-PCR) analysis confirmed successful integration and expression of Lu-PLR gene. Quantitative analysis of phyllanthin performed on transgenic and wild plants using high-performance liquid chromatography (HPLC) revealed that transgenic lines contained higher phyllanthin content (0.3–0.81% w/w) than wild plants (0.09% w/w). The highest yield of phyllanthin was detected in transgenic lines was up to 1.16, 1.22 and 1.23 folds higher than that of wild plant. This report highlights the transgenic approach to enhance the contents of phyllanthin and hypophyllanthin.     

A chalcone synthase gene <Emphasis Type="Italic">AeCHS</Emphasis> from <Emphasis Type="Italic">Abelmoschus esculentus</Emphasis> regulates flavonoid accumulation and abiotic stress tolerance in transgenic <Emphasis Type="Italic">Arabidopsis</Emphasis>

Chalcone synthase (CHS) is one of the key enzymes in flavonoid biosynthesis pathway in plants. However, the roles of AeCHS gene from Abelmoschus esculentus in flavonoid accumulation and tolerance to abiotic stresses have not been studied. In this study, the AeCHS gene was cloned from Abelmoschus esculentus. The open reading frame contained 1170 nucleotides encoding 389 amino acids. The coding region of AeCHS was cloned into a binary vector under the control of 35S promoter and then transformed into Arabidopsis to obtain transgenic plants. Overexpression of AeCHS increased the production of downstream flavonoids and the expression of related genes in the flavonoid biosynthesis pathway. It also improved resistance to salt and mannitol stresses during seed germination and root development. Further component and enzymatic analyses showed the decreased content of H₂O₂ and malondialdehyde and the increased activities of superoxide dismutase (SOD) and peroxidase (POD) in transgenic seedlings. Meanwhile, the expression level of AtSOD and AtPOD genes was up-regulated against salt and osmotic stresses. Together, our finding indicated that changing the expression level of AeCHS in plants alters the accumulation of flavonoids and regulates plantlet tolerance to abiotic stress by maintaining ROS homeostasis. The AeCHS gene has the potential to be used to increase the content of valuable flavonoids and improve the tolerance to abiotic stresses in plants.     

<Emphasis Type="Italic">Sr33</Emphasis> and <Emphasis Type="Italic">Sr35</Emphasis> gene homolog identification in genomes of cereals related to <Emphasis Type="Italic">Aegilops tauschii</Emphasis> and <Emphasis Type="Italic">Triticum monococcum</Emphasis>

Using bioinformatics analysis, the homologs of genes Sr33 and Sr35 were identified in the genomes of Triticum aestivum, Hordeum vulgare, and Triticum urartu. It is known that these genes confer resistance to highly virulent wheat stem rust races (Ug99). To identify amino acid sites important for this resistance, the found homologs were compared with the Sr33 and Sr35 protein sequences. It was found that sequences S5DMA6 and E9P785 are the closest homologs of protein RGAle, a Sr33 gene product, and sequences M7YFA9 (CNL-C) and F2E9R2 are homologs of protein CNL9, a Sr35 gene product. It is assumed that the homologs of genes Sr33 and Sr35, which were obtained from the wild relatives of wheat and barley, can confer resistance to various forms of stem rust and can be used in the future breeding programs aimed at improvement of national wheat varieties.     

The <Emphasis Type="Italic">Adh</Emphasis> locus and adaptation of <Emphasis Type="Italic">cn</Emphasis> and <Emphasis Type="Italic">vg</Emphasis> mutants in experimental populations of <Emphasis Type="Italic">Drosophila melanogaster MEIG</Emphasis>

A complex study on the adaptation of cn and vn mutants and the allozymes of alcoholdehydrogenase (ADH) was carried out in initially pure lines, and their panmixia populations during exchange of the mutant genotype with that of wild-type flies (C-S) and D) through saturating crossings. The relative adaptation of the genotypes was estimated by their effect on reproductive efficiency in the experimentally obtained population. Fecundity, lifespan, and the resistance of the studied genotypes to hyperthermia were investigated individually. It was shown that the high level of adaptation of the cn mutants and the low level of adaptation of the vg mutants was correlated with the presence of different ADH allozymes. In the studied population, the F-allozyme of ADH accompanied the vg mutation, while the S-allozyme of the enzyme was detected in cn mutants. Saturating crossings of C-S(Adh ^S)×vg(Adh ^F) and D(Adh ^F) × cn(Adh ^S), along with the parallel determination of the allele composition of the Adh locus, demonstrated that the complete substitution of the F-allozyme of ADH in the vg mutants by the S-allozyme in D flies, as well as the substitution of the S-allozyme of ADH in the cn mutants by the F-allozyme in D flies was realized only after the 15th–20th backcrosses. These results favor the coadaptation of cn and vg marker genes with alleles of the Adh locus and indicate the important role of the latter in the adaptation of genotypes. In the studied population, selection acted primarily against the vg mutants, which were inferior to the cn mutants, and heterozygote genotypes in indices of the main adaptation components.     

Role of Arabidopsis <Emphasis Type="Italic">ABF1</Emphasis>/<Emphasis Type="Italic">3</Emphasis>/<Emphasis Type="Italic">4</Emphasis> during <Emphasis Type="Italic">det1</Emphasis> germination in salt and osmotic stress conditions

Key message

Arabidopsis det1 mutants exhibit salt and osmotic stress resistant germination. This phenotype requires HY5, ABF1, ABF3, and ABF4.

Abstract

While DE-ETIOLATED 1 (DET1) is well known as a negative regulator of light development, here we describe how det1 mutants also exhibit altered responses to salt and osmotic stress, specifically salt and mannitol resistant germination. LONG HYPOCOTYL 5 (HY5) positively regulates both light and abscisic acid (ABA) signalling. We found that hy5 suppressed the det1 salt and mannitol resistant germination phenotype, thus, det1 stress resistant germination requires HY5. We then queried publically available microarray datasets to identify genes downstream of HY5 that were differentially expressed in det1 mutants. Our analysis revealed that ABA regulated genes, including ABA RESPONSIVE ELEMENT BINDING FACTOR 3 (ABF3), are downregulated in det1 seedlings. We found that ABF3 is induced by salt in wildtype seeds, while homologues ABF4 and ABF1 are repressed, and all three genes are underexpressed in det1 seeds. We then investigated the role of ABF3, ABF4, and ABF1 in det1 phenotypes. Double mutant analysis showed that abf3, abf4, and abf1 all suppress the det1 salt/osmotic stress resistant germination phenotype. In addition, abf1 suppressed det1 rapid water loss and open stomata phenotypes. Thus interactions between ABF genes contribute to det1 salt/osmotic stress response phenotypes.