Sucrose is a dominant sugar transported to the sink organs of a plant where it is metabolized to other compounds or stored. Here, the importance of sucrose metabolism in a drought-tolerant wheat cultivar was compared to a drought-sensitive one. The 4-d-old Triticum aestivum L. seedlings were exposed to drought induced by water cessation for 7 d and recovery after re-watering for further 7 d. Under control conditions, constitutive expression of genes encoding vacuolar invertase (VI) and sucrose synthase (SuS) and activity of sucrose phosphate synthase (SPS) were significantly higher in the tolerant cultivar than in the sensitive one. Drought promoted the expressions of SPS and VI genes in the tolerant cultivar and increased their activities to 175 and 132 %, respectively, of those under control conditions. The activity of SuS and expression of its gene, however, were identical in both cultivars under drought stress. These changes resulted in more remarkable accumulation of sucrose in tolerant than in sensitive cultivar under water stress.

Root epidermis and apoplastic barriers (endodermis and exodermis) are the critical root structures involved in setting up plant-soil interface by regulating free apoplastic movement of solutes within root tissues. Probing root apoplast permeability with "apoplastic tracers" presents one of scarce tools available for detection of "apoplastic leakage" sites and evaluation of their role in overall root uptake of water, nutrients, or pollutants. Although the tracers are used for many decades, there is still not an ideal apoplastic tracer and flawless procedure with straightforward interpretation. In this article, we present our experience with the most frequently used tracers representing various types of chemicals with different characteristics. We examine their behaviour, characteristics, and limitations. Here, we show that results gained with an apoplastic tracer assay technique are reliable but depend on many parameters-chemical properties of a selected tracer, plant species, cell wall properties, exposure time, or sample processing.

Zinc nutrition of tea (Camelia sinensis) have a great impact on acclimation to dehydration stress and on improvement of stress recovery. Dehydration stress induced by withholding water for 7 d decreased relative water content, dry mass of leaf, and content of antioxidants like ascorbate and glutathione and increased H₂O₂ content and lipid peroxidation and changed activities of superoxide dismutase, catalase, peroxidase, and glutathione reductase. A pre-treatment with 0.1 and 0.5 mM ZnSO₄ minimized these effects and increased Zn uptake. Further, foliar spray with 0.1 and 0.5 mM ZnSO₄ before rehydration lowered H₂O₂ generation, increased content of antioxidants and activities of antioxidative enzymes, and decreased lipid peroxidation. The present findings suggest that zinc regulates water stress responses and recovery after rehydration in tea.

ABC transporters, which comprise one of the largest protein families, are involved in maintaining osmotic homeostasis, nutrient uptake, pathogen resistance, and metal tolerance. In this study, 30 ABC genes in dwarf polish wheat were characterized and classified into seven subfamilies (ABCA - ABCG). Among them, 24 ABC transporters were newly found in wheat. The expressions of 13 ABC genes in roots and leaves under six metal stresses were also analyzed. All these genes were differentially regulated by Cd (except ABCE2, ABCF4, and ABCF6 in roots), suggesting that these genes participate in Cd transport, sequestration, or uptake. These genes were also differentially regulated by other metals including Cu, Mg, Zn, Fe, and Ni. Results suggest that the expressions of ABC transporters in dwarf polish wheat played important roles in metal transport and detoxification.

The presence of solar radiation is one of the most important environmental factors, which is required for the optimal growth and development of plants. The absence of it (e.g. in the night period or artificially prolonged darkness) can alter the light-dependent signalling and regulation pathways and may induce new defence responses. Antioxidant enzymes as components of the plant defence system play a crucial role in the detoxification of reactive oxygen species (ROS) induced by several stressors; however, their regulation can be different in the light or in the dark. In this review we summarize the current knowledge about the physiological and molecular aspects of dark-modulated key antioxidant enzymes (superoxide dismutase, catalase, and ascorbate peroxidase) in different plant species and discuss their roles in different developmental processes (seedling growth and development or senescence) and in responses to environmental stresses (cold, chilling, heat, and biotic stress). Moreover, the hormonal regulation of respective gene transcription and the changes in activity of various isoenzymes at subcellular level are also summarized. Based on this knowledge, modification of these antioxidant enzymes may be used to increase the yield and stress tolerance of cultivated plants in the changing environment.

Tomato (Solanum lycopersicum) plants have four fructokinase genes, SlFRK1-4. The SlFRK4 is expressed only in pollen whereas the other three are expressed in all plant parts. While SlFRK2 and SlFRK3 are involved in vascular tissue development and affects the shape, size, and cell-wall width of xylem vessels and xylem fibers, the role of SlFRK1 has not been studied previously. The current work investigates the expression of SlFRK1 using transgenic tomato plants expressing the β-glucuronidase reporter gene under the SlFRK1 promoter, as well as the role of SlFRK1 using transgenic plants with antisense suppression of SlFRK1. The SlFRK1 promoter is expressed primarily in vascular tissues and specific suppression of SlFRK1 reduces water transport in stems, but has no other anatomical or phenotypic effects. Combined suppression of SlFRK1 and SlFRK2 severely inhibited plant growth and an anatomical analysis revealed a reduction in secondary xylem area and distorted phloem fibers characterized by thin cell walls and reduced lignification. The results suggest that SlFRK1 is involved in vascular tissue development and hydraulic conductivity in tomato plants and that SlFRK1 is important for normal phloem fiber development, together with SlFRK2.

The proposed work describes a protocol for high-frequency in vitro regeneration through nodal segments and shoot tips in Decalepsis arayalpathra, a critically endangered medicinal liana of the Western Ghats. Nodal segments were more responsive than shoot tips in terms of shoot proliferation. Murashige and Skoog's (MS) basal medium supplemented with 5.0 μM 6-benzyladenine (BA) was optimum for shoot initiation through both the explants. Among different combinations of plant growth regulators and growth additive screened, MS medium added with 5.0 μM BA + 0.5 μM indole-3-acetic acid + 20.0 μM adenine sulphate effectuated the highest response: 11.8 shoots per nodal segment and 5.5 shoots per shoot tip with mean shoot length of 9.2 and 4.8 cm, respectively. Half-strength MS medium with 2.5 μM α-naphthalene acetic acid was optimum for in vitro root induction. The plantlets with the well developed shoot and root were acclimatized in Soilrite™ with 92 % survival rate in the field conditions. During acclimatization, chlorophyll content, net photosynthetic rate, stomatal conductance, and transpiration rate were gradually changed in dependence of formation of new leaves. Further, the changes in activities of antioxidant enzymes, i.e., superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) as well as activity of carbonic anhydrase were also observed: a continuous rise in SOD activity, but a rise and fall in the activities of CAT, APX, and GR were also noticed. Maximum fresh mass (3.1 g plant^-1), dry mass (0.35 g plant^-1) of roots and 2-hydroxy-4-methoxybenzaldehyde content of 9.22 μg cm^-3(root extract) were recorded after 8 weeks of acclimatization.

The effects of silver nanoparticles (AgNPs), silver ions (Ag⁺), and polyvinylpyrrolidone (PVP) on mitosis and expression of a gene encoding cyclin-dependent kinase 2 (cdc2) in onion roots were compared. Three concentrations (5, 10, and 15 mg dm^-3) were employed in combination with three incubation times (3, 6, and 9 h). PVP enhanced mitotic index and cdc2 expression. Both silver forms decreased mitotic index and cdc2 expression. Genotoxicity of both silver forms were indicated by three major distinguishable classes of chromosome aberrations: spindle disturbances, clastogenic aberrations, and chromosome stickiness. Concerning Ag⁺ treatments, significant enhancements in occurrence of any chromosome aberration type was associated with significant decrease in mitotic index. On the other hand, disturbed spindle in AgNPs treatments was observed even in absence of significant reduction in mitotic index suggesting that AgNPs inhibit cellular events occurring during mitosis to proceed normally rather than starting of cell division.

Osmotic stress causes a series of morphological, physiological, biochemical, and molecular changes that alters plant growth, development, and productivity around the globe. Phytohormones, nutrients, and transcription factors may induce adaptive responses to osmotic stress in plants. We evaluated the effect of osmotic stress induced by 18.5 % polyethylene glycol (PEG) or 100 mM NaCl on growth, content of abscisic acid (ABA), chlorophyll (Chl), sodium, and potassium, and the expression of multifunctional NAC transcription factors in rice cultivars (the salt-tolerant Cotaxtla and salt-sensitive Tres Ríos). The PEG and NaCl decreased shoot height and increased ABA content in both cultivars, and reduced root length in cv. Tres Ríos. The PEG increased Chl content in cv. Cotaxtla leaves. NaCl reduced shoot K⁺ content in cv. Tres Ríos and increased shoot and root Na⁺ content in both cultivars, thus resulting in a decreased K⁺/Na⁺ ratio. Of the 57 NAC genes evaluated, two of them were repressed (Os10g42130 and Os07g04560) and two other induced (Os02g34970 and OsNAC10) in cv. Cotaxtla in response to PEG, whereas three of them were repressed (Os10g42130, Os07g04560 and Os08g10080), and six induced (Os02g56600, Os02g34970, Os11g08210, Os05g34830, OsNAC6, and OsNAC10) in response to NaCl. In the cv. Tres Ríos, we found two genes repressed (Os10g42130 and Os07g04560), and five induced (Os08g33910, Os03g60080, Os06g51070, OsNAC6, and OsNAC10) in response to PEG, while only two genes were repressed (Os10g42130 and Os07g04560) but 13 induced (Os03g21060, Os08g39110, Os03g60080, Os01g15640, Os06g51070, Os09g33490, Os04g40130, Os12g29330, Os02g36880, Os11g08210, Os05g34830, OsNAC6, and OsNAC10) by NaCl. Osmotic stress affected more severely cv. Tres Ríos than cv. Cotaxtla plants. These different responses might be regulated by ABA and NAC transcription factors.

Brassinosteroids (BRs) are plant hormones that were isolated for the first time in the 1970s. This group currently includes more than 70 compounds that differ in their structure and physiological activity. BRs are present in plants in a free form or in the form of conjugates. BRs are known as plant growth regulators, but they also play a role in the plant response to environmental stresses. In the case of plants that are exposed to low/high temperature, exogenous BRs can counteract growth inhibition and reduce biomass losses as well as increase plant survival. BRs show a multidirectional activity in regulating the metabolism of plants exposed to extreme temperatures. The following BRs actions can be distinguished: changes in membrane physicochemical properties, regulation of the expression of selected genes (including stress-responsive genes), as well as indirect effects on metabolism through other hormones or signalling molecules (such as hydrogen peroxide). This review summarizes the current knowledge about the effects of BRs on the physiological and biochemical processes that occur in plants during exposure to low or high temperatures.

Downy mildew caused by Hyaloperonospora parasitica is a serious fungal disease in non-heading Chinese cabbage (Brassica campestris L. ssp. chinensis Makino). Pathogenesis-related 5 (PR-5) genes play an important role in plant resistance to disease invasion. In this study, a gene encoding pathogenesis-related 5-like (PR-5L) protein, named BcPR-5L, was successfully cloned from non-heading Chinese cabbage. The cDNA sequence of BcPR-5L is 747 bp in length. It encoded a protein of molecular mass of 25.78 kDa, an isoelectric point of 4.42, and containing 248 amino acids. Multiple sequence alignment indicated that BcPR-5L protein was highly homologous to other PR-5L proteins identified in 13 different species, with the highest homology to Brassica rapa. We analyzed the subcellular localization of BcPR- 5L protein by using onion epidermal cells and found that it is localized in the membrane. Real time quantitative PCR analyses revealed that the expression of BcPR-5L gene was significantly upregulated after H. parasitica infection, and the expression in the resistant cultivar was higher than that in the susceptible cultivar. In summary, our data suggest that BcPR-5L gene may play an important role in the resistance of non-heading Chinese cabbage to H. parasitica infection.

Leaf anatomy and irradiance-dependent leaf transmittance changes serving as irradiance acclimation mechanisms in leaves were studied in two ecologically contrasting Tradescantia species, a shade plant T. fluminensis Vell. and a sun plant T. sillamontana Matuda, grown at different irradiances. A dramatic increase in leaf thickness (2 to 4-fold) under a high growth irradiance (800 μmol m^-2 s^-1) compared with a low growth irradiance (60 μmol m^-2 s^-1), achieved mainly by expansion of the epidermis, was recorded in both species. The effect took place on the background of modest changes in mesophyll thickness (1.8-fold in T. fluminensis and 1.15-fold in T. sillamontana) and chloroplast size (0.8-fold in T. fluminensis and an insignificant change in T. sillamontana). Mesophyll structure and growth irradiance response did not seem to facilitate significantly light-dependent chloroplast (avoidance) movement in these species. Nevertheless, an exceptionally large (2 to 4-fold) irradiance-induced increase in light transmittance attributable to chloroplast avoidance movement was revealed. This increase by far exceeded that in other higher plants according to available literature. The magnitude of the irradiance-dependent transmittance changes positively correlated both with the rate of photosystem II recovery and with the extent of xanthophyll deepoxidation in the leaves. This was opposite to a negative correlation observed between the same parameters in different plant species. We hypothesize that, at the evolutionary timescale, chloroplast avoidance movement might adjust independently from other photoprotective mechanisms, e.g., non-photochemical quenching, whereas, on the ontogenetic timescale, adjustment of these mechanisms inevitably follows the same trend.

The aim of this study was to identify single nucleotide polymorphism (SNP) markers genetically linked to root elongation rate (RER) in sugar beet (Beta vulgaris L.). A population of 244 F₃ individuals, obtained from the cross between lines L01 (a low RER) and L18 (a high RER), was phenotyped by measuring RER of 11-d-old seedlings grown in a hydroponic culture. Two DNA bulks of 50 F₃ individuals with extreme phenotypes were used for bulk segregant analysis by restriction-associated DNA sequencing. A total of 20 376 SNPs were identified. Single nucleotide polymorphisms were filtered to reduce the number of the false positive and mapped on candidate chromosomal regions of the B. vulgaris reference genome. One of the total of SNPs selected, SNP10139, was strongly linked to RER (P < 0.01). The pattern of association between the SNP10139 genotype and RER was also evaluated on a breeding line panel comprising 40 low and 40 high RER individuals with different allele frequencies between groups (P < 0.01). The SNP10139 sequence was mapped on the B. vulgaris peptide transporter (PTR) gene, a carrier that influences root elongation in Arabidopsis thaliana. Our results suggest that SNP10139 influence RER in sugar beet, and sequence information can be used in marker-assisted selection programs.

Seasonal growth is characteristic for many tree species including almond. Varying conditions during the season are responsible for growth cessation, bud set, dormancy entry, cold hardening, and bud burst. Here, we report the characterization of an almond homologue of the Arabidopsis GIGANTEA (AtGI) gene (designated as PdGI, GenBank accession No. KJ502316). We propose a role for this gene in the transition to dormancy and cold acclimation. The complementary DNA (cDNA) sequence of PdGI was 4 322 bp long and contained an open reading frame of 3 512 bp. The deduced amino acid sequence of PdGI shared 76 % identity with AtGI. The expression of PdGI at ambient day/night temperatures of 22/20 ºC was differentially regulated under a 16-h or 12-h photoperiod, increasing during the day and decreasing after dusk. However, this diurnal regulation was disrupted when plants were transferred to cold (12 ºC) conditions. In addition, we have assessed the expression of PdGI and putative almond homologues of the downstream target genes CONSTANS (PdCO-like) and FLOWERING LOCUS T (PdFT-like) in flower buds and shoots from adult trees during the bud break period in autumn and early winter. Our results show a clear increase in transcript abundance towards anthesis, suggesting a role of these genes in flower development.

Boron (B) is an essential plant micronutrient. Two major B-transport proteins have been recently identified and partially characterized: BOR1, a high-affinity B efflux transporter involved in xylem loading, and NIP5;1, a plasma-membrane boric-acid channel involved in B uptake. To date, studies of these B transporters have investigated their expression individually (mainly as mRNA), and only in response to variation in B availability (mostly B deficiency); the influence of other factors, such as plant resource status, has not been studied. To address this, we grew geranium (Pelargonium × hortorum cv. Maverick White) plants under ambient or elevated CO₂ concentration, different sub-saturating irradiances, and different B availability. For comparison we also grew three other species (Arabidopsis thaliana, Azolla caroliniana, and Hordeum vulgare) under broad range of B supply. Relative accumulation of BOR1 and NIP5;1 proteins were measured using protein-specific antibodies and Western blotting or ELISA. Elevated CO₂ significantly increased content of NIP5;1, while increases in irradiance increased BOR1 content, but decreased NIP5;1 content. Across species, content of both transporters often decreased with increasing B availability, but sometimes remained unchanged or even increased, depending on CO₂, irradiance, species, or transporter. Content of BOR1 and NIP5;1 was correlated with root proteins, B content, and sugar content (for high CO₂ only), as well as B uptake, but CO₂ and irradiance often affected these relationships. Thus, relative accumulation of BOR1 and NIP5;1 is influenced not only by B content, as expected, but by other environmental factors as well.

This review reports the physiological and metabolic changes in plants during development under elevated atmospheric carbon dioxide concentration and/or limited-nitrogen supply in order to establish their effects on leaf senescence induction. Elevated CO₂ concentration and nitrogen supply modify gene expression, protein content and composition, various aspects of photosynthesis, sugar metabolism, nitrogen metabolism, and redox state in plants. Elevated CO₂ usually causes sugar accumulation and decreased nitrogen content in plant leaves, leading to imbalanced C/N ratio in mature leaves, which is one of the main factors behind premature senescence in leaves. Elevated CO₂ and low nitrogen decrease activities of some antioxidant enzymes and thus increase H₂O₂ production. These changes lead to oxidative stress that results in the degradation of photosynthetic pigments and eventually induce senescence. However, this accelerated leaf senescence under conditions of elevated CO₂ and limited nitrogen can mobilize nutrients to growing organs and thus ensure their functionality.

Root cortical aerenchyma (RCA) is suggested to reduce metabolic cost for root growth, but it might lower water uptake by plants. The objective of this work was to evaluate the effects of drought and phosphorus on the RCA development along the root axis and to elucidate its role in water stress tolerance of two maize genotypes. Plants of drought-tolerant DKB390 and drought-sensitive BRS1010 genotypes were grown in Vermiculite at field capacity of 100, 75, 50, and 25 % and supplied with 0.1, 0.4, and 0.8 mM phosphorus. Growth parameters, RCA, and plant P content were evaluated for all plants. Higher RCA development was observed in DKB390 than in BRS1010. Drought reduced the percentage of RCA in the root-hair zone of both genotypes but increased its development in the root maturation zone. Phosphorus limitation enhanced RCA development only in the DKB390. Under drought stress, DKB390 showed resilient growth whereas growth was inhibited in BRS1010. Higher root P content was related to its higher supply. Therefore, RCA formation was induced either by drought or by phosphorus limitation, while no interaction was evident. The RCA development varied along the root axis in order to balance water and phosphorus uptake and the drought response was genotype dependent.

Heat stress, one of the major abiotic stresses in wheat, affects chlorophyll fluorescence and chlorophyll content and thereby photosynthesis. To identify quantitative trait loci (QTLs) associated with these traits under terminal heat stress, 251 recombinant inbred lines (RILs) derived from a cross HD 2808/HUW510 were phenotyped. Using composite interval mapping, 40 QTLs were identified; 17 were related to conditions after timely sowing and 23 to heat stress after late sowing. The various parameters of chlorophyll fluorescence were associated with 23 QTLs, which were located on chromosomes 1A, 2A, 3A, and 2D and explained 3.67 to 18.04 % of phenotypic variation, whereas chlorophyll content was associated with 17 QTLs on chromosomes 2A, 2B, 2D, 5B, and 7A explaining 3.49 to 31.36 % of phenotypic variation. Most of the identified QTLs were clustered on chromosome 2D followed by 2A and 1A. The QTL Qchc.iiwbr-2A for chlorophyll content linked with marker gwm372 was stable over conditions and explained 3.81 to 18.05 % of phenotypic variation. In addition, 7 epistatic QTL pairs were also detected which explained 1.67 to 11.0 % of phenotypic variance. These identified genomic regions can be used in marker assisted breeding after validation for heat tolerance in wheat.

In Arabidopsis, EXPORTIN1A (HIT2/XPO1A) and EXPORTIN1B (XPO1B) mediate the translocation of nuclear export sequence (NES)-bearing proteins from nucleus to cytoplasm. However, a mutation in HIT2/XPO1A but not in XPO1B induces sensitivity to high irradiance (HI). Arabidopsis thaliana heat stress elements A4a and A5 (AtHsfA4a and AtHsfA5) are involved in plant responses to HI and possess NESs; therefore, their nucleo-cytoplasmic partitioning was analyzed. In wild-type and xpo1b mutant cells, AtHsfA4a normally remained in the cytoplasm but became concentrated in the nucleus following exposure to HI, whereas AtHsfA5 was constitutively distributed in both cytoplasm and nucleus. However, in hit2/xpo1a mutant, AtHsfA4a and AtHsfA5 were always confined to the nucleus, regardless of the irradiance. Although AtHsfA4a can enhance the ability of plants to scavenge H₂O₂, and AtHsfA5 is a repressor of AtHsfA4a, athsfa5 but not athsfa4a mutant plants exhibited HI sensitivity. Additionally, athsfa4a plants expressing AtHsfA4aΔNES were sensitive to HI, but athsfa5 plants expressing AtHsfA5ΔNES were not. Meanwhile, hit2/athsfa4a double mutant was more tolerant to HI than hit2. These results indicate that both AtHsfA4a and AtHsfA5 were HIT2/XPO1A-specific substrates. Long-term accumulation of AtHsfA4a contributed to the hit2 HI-sensitive phenotype independent of the scavenging ability of H₂O₂, and the presence of AtHsfA5 could mitigate this adverse effect.

Auxins are one of the main regulators of in vitro plant growth and development. However, the mechanisms, by which auxins, such as 1-naphthaleneacetic acid (NAA), affect in vitro root and leaf anatomy and photosystem function, remain unclear. Accordingly, the aim of the present study was to analyze the effect of different NAA concentrations on the anatomy and photosynthetic performance of in vitro-propagated Aechmea blanchetiana and to determine whether such a treatment affects micropropagated plants after acclimatization. In vitro-established A. blanchetiana plants were transferred to culture media that contained 0, 2, 4, or 6 μM NAA, and after 50 d, they were transplanted into plastic seedling trays with a commercial substrate and cultivated for 60 d in a greenhouse. The plants were evaluated after a 50-d in vitro NAA exposure (growth traits, chlorophyll α fluorescence, and root and leaf anatomy) and after 60 d of acclimatization in the greenhouse (root and leaf growth). Changes induced by NAA in root anatomy might improve uptake of minerals and sugars from the medium, thereby increasing the in vitro growth. In the leaves, the lowest chlorenchyma thickness and sclerenchyma area were observed in plants grown without NAA, and NAA exposure also improved photosystem II activity. The highest ex vitro growth rate was observed for plants that were propagated with 4 μM NAA. Therefore, the use of NAA during in vitro propagation can improve the anatomical and physiological quality of A. blanchetiana plants, as well as to improve ex vitro transfer.

Brassinosteroids (Brs) have drawn wide attention due to their protective role against toxicity of heavy metals in plants. To better understand the role of Br in arsenic (As) and cadmium (Cd) uptake by rice plants, a hydroponic experiment was conducted to investigate the combined effect of 24-epibrassinolide (Br24) or 28-homobrassinolide (Br28) and iron plaque (IP) on As and Cd uptake and accumulation in rice seedlings. Six-week-old seedlings were sprayed with 0.2 or 0.02 μM Br24 or Br28 and grown in nutrient solution for 3 d, and then 20 or 60 mg Fe²⁺ dm^-3 (Fe20 and Fe60) was used to induce root IP formation for 3 d. These seedlings with or without Br and with or without IP were exposed to solution containing 0.5 mg dm^-3 As^III or Cd for 9 d. The results showed that rice growth decreased when Br24 were applied, but it increased when combination of Br24 and IP was applied. Fe concentrations in dithionite-citratebicarbonate (DCB) extracts were increased after 0.2 or 0.02 μM Br24 application in the absence of IP, but decreased by Br24 in the presence of IP. In the absence of IP, As and Cd content in leaves was significantly reduced by 0.02 μM Br24 and 0.2 μM Br28, respectively. The As content in leaves was also reduced by the combination of 0.02 and 0.2 μM Br28 and IP, and the Cd content in leaves was reduced by the combined effect of 0.2 μM Br24 and IP. These results indicate that Br24 and Br28 could impede As and Cd accumulation, and the interactions between Br and IP may have a potential in restricting the transport of As and Cd into rice shoots.

The effects of copper and zinc salts on transgenic canola plants expressing rice transcription factor (TF) OsMYB4 were investigated. Transgenic plants (TPs), which showed a high OsMyb4 expression in response to either Cu or to Zn excess, were used for the current study. In leaves of TPs, the content of Cu was equal and the content of Zn was significantly higher than in non-transformed plants (NTPs). The TPs grown on an extremely high concentration of heavy metals (HMs; 150 μМ CuSO₄ or 5 000 μМ ZnSO₄) were able to survive for more than 15 d, while NTPs died after 7 - 9 d of incubation. This indicates that expression of OsMyb4 in canola plants improved their HM tolerance. The TPs tolerance to HMs was confirmed by a higher shoot biomass than that in NTPs. Excess of HMs caused oxidative stress (indicated by increase in malondialdehyde content) especially in leaves of NTPs. This data suggests a protective role of the OsMyb4 TF in oxidative stress. The HMs caused a lower decrease in activities of superoxide dismutase and guaiacol peroxidase in TPs than in NTPs. Higher tolerance of TPs to HMs was also suggested by a considerable increase in the content of low-molecular phenolic compounds, including flavonoids and anthocyanins, as well as proline (a potential antioxidant and chaperone). These data suggest that OsMYB4 may play a role as a positive regulator of phenylpropanoid pathway and proline synthesis. The created canola OsMyb4 TPs may be useful for future applications in phytoremediation of HM-polluted soils.

Papaya (Carica papaya L.) is susceptible to viral diseases caused by Papaya mosaic virus (PapMV) and Papaya ringspot virus (PRSV), which limit fruit production and affect economic yield. The symptoms produced by both the viruses are similar in early stages of infection and include vein and leaf chlorosis, which develop into mosaic at later stages of infection when leaf lamina can get reduced in size and distorted with a shoe-string aspect. Digital image analyses, such as fractal dimension (FD) and lacunarity (λ) were used here to examine papaya tissue after single and mixed infections of PRSV and PapMV. Morphological changes, such as hypoplasia, hyperplasia, and neoplasia are described in tissues with viral infections. Furthermore, we quantified these changes and suggest three ranges of tissue damage according to their λ values in rank 1 (0.01 to 0.39), rank 2 (0.4 to 0.79), and rank 3 (0.8 to 1). Our analyses suggest that in synergism and antagonism there is a competition of both viruses to occupy the same mesophyll cells, as indicated by their intermediate values of lacunarity.

The miR171 is a conserved microRNA (miRNA) family and has been shown to participate in plant growth and development. However, the precise function of miR171 in Pinus densata remains largely unclear. Mature miR171 sequence comparison reveals high similarity between Arabidopsis thaliana and P. densata and the pre-miR171 could fold into a characteristic stem-loop hairpin structure. Genes encoding GRAS (GAI-RGA-SCR) family transcription factors and actin binding protein were identified as targets of pde-miR171 using a modified RNA ligase mediated 5' rapid amplification of cDNA ends (RLM-RACE). Furthermore, the interaction between pde-miR171 and Arabidopsis SCL6 (SCARECROW-LIKE6) was further validated through transient co-expression of both genes in Nicotiana benthamiana leaves. Next, results of real-time quantitative PCR demonstrated that the expression of pde-miR171 was significantly up-regulated in miR171-overexpressing plants than in wild-type plants, which was inversely correlated with the expression of Arabidopsis SCL6 genes. In addition, overexpression of pde-miR171 in Arabidopsis induced larger leaves and earlier flowering under long-day conditions compared with the wild type. The findings presented here suggest that miR171 derived from a P. densata precursor together with its target gene SCL6 may play important roles in the regulation of primary root growth, leaf shape, and flowering time in plants.

Gibberellin 2-oxidases (GA2oxs) irreversibly convert bioactive gibberellins (GAs) and their immediate precursors into inactive GAs via 2-β hydroxylation and so regulate gibberellin content in plants. However, to the best of our knowledge, little has been known about the GA2oxs and its function in cool season turfgrass Poa pratensis. In this study, rapid amplification of cDNA end (RACE) was employed to isolate PpGA2ox from P. pratensis. The open reading frame of PpGA2ox was 1 047 bp in length, corresponding to 348 amino acids. PpGA2ox was localized in both nucleus and cytoplasm. The expression of PpGA2ox could be up-regulated by 10 μM gibberellic acid, 5 μM methyl jasmonate, or 10 μM indole-3-acetic acid. In addition, its native promoter could drive GUS expression in both leaf apex and shoot apical region. Moreover, overexpression of PpGA2ox in Arabidopsis led to GA-deficiency leading to dwarf phenotype, delayed flowering time, and increased chlorophyll content. Our study suggests that PpGA2ox could be a candidate gene for breeding new cultivars of P. pratensis.

Salinity is one of the major abiotic constraints to agriculture. The physiological and molecular mechanisms of salt tolerance have been studied in plants for many years. The regulation of osmosis and ion homeostasis is crucial. A lot of important components involved in plant responses to salt stress have been identified. Among them, ion transporters and channels take an essential role in ion homeostasis, mainly for Na⁺, Cl^-, and K⁺. Until now, many cation antiporters important for salt tolerance in plants have been characterized. Among them, the monovalent cation/proton antiporters (CPA) family is one of the most important families, including sodium proton exchangers (NHXs), K⁺-efflux antiporters (KEAs), and cation/H⁺ exchangers (CHXs). Here, the current knowledge of the plant CPA family in responses to salt stress was reviewed. The regulation mechanisms were also included and discussed.

With the dramatic increase in nanotechnologies, it has become probable that biological systems will be exposed to excess of nanoparticles (NPs). However, the impact of NPs on plants, remains to be explored. The aim of this research was to determine the effects of ZnO NPs on tomato (Solanum lycopersicum L.) plants. Plant growth, photosynthetic characteristics, chlorophyll fluorescence parameters, and activities of antioxidative enzymes were measured in 35-d-old plants. The ZnO NP treatments significantly inhibited tomato root and shoot growth, decreased the content of chlorophylls a and b, and reduced photosynthetic efficiency and some other chlorophyll fluorescence parameters in a concentration-dependent manner. However, the supernatant of ZnO NP suspensions did not affect growth of tomato, despite the presence of small amounts of Zn²⁺. Taken together, these results suggest that toxic effects on tomato plants were from ZnO NPs, not from Zn²⁺ released into the solution; toxicity was likely caused by reduced chlorophyll content and damaged photochemical system, which in turn limited photosynthesis and led to the reduction in biomass accumulation. Also, ZnO NPs enhanced the transcription of genes related to antioxidant capacity, suggesting that ZnO NPs could enhance the defence response by increasing activities of antioxidant enzymes.

The tubular ray flower (turf) mutant of sunflower is characterized by a switch of ray flowers from zygomorphic to near-actinomorphic disc flowers. In sunflower, floral symmetry of ray and disc flowers is specified by the activity of members of a CYCLOIDEA (CYC) gene family. The turf mutant is generated by the insertion of a CACTA-like transposable element (TE), named Transposable element of turf1 (Tetu1), in the coding sequence of the HaCYC2c gene. The TEinsertion changes the reading frame of turf-HaCYC2c for the encoded protein and leads to a premature stop codon. Tetu1 is a non-autonomous version of a CACTA TEcarrying the minimum sequences necessary for transposition in the presence of autonomous elements in the sunflower genome. In the previous analysis, performed in more than 11 000 plants homozygous for the turf-HaCYC2c allele, the absence of chimerism and the segregation rate of derived-progenies from reverted phenotypes suggest that Tetu1 transpositions are restricted to a time shortly before and/or during meiosis. Here, we report the analysis of F₅ and F₆ progenies, derived from an F₄ progeny of the cross turf × Chrysanthemoides2, where plants with a chimeric inflorescence were detected. Tetu1 showed active excision in all progenies taken into consideration and named High Frequency of Tetu1 Transposition (HFTT). Within a total of 449 plants, Tetu1 excision generated a 13.81 % of non-chimeric revertants but also a 5.12 % of plants with somatic sectors of variable size in the outmost whorl of the inflorescence. These unexpected results suggest variations in tissue specificity and time of TEexcision. The excision of Tetu1 was confirmed by DNA molecular screening of non-chimeric and chimeric revertants and transcription analysis of the HaCYC2c gene. In HFTT progenies, sequence analyses excluded significant DNA changes with respect to the original Tetu1 transposon as well as to the adjacent 5'- and 3'-TE regions. Genetic and epigenetic regulatory mechanisms were proposed to explain the time and frequency of Tetu1 transposition in HFTT progenies.

To facilitate functional genomic analysis and molecular breeding of velvet ash (Fraxinus velutina Torr), the de novo sequencing was carried out by Illumina sequencing technology. The cDNA samples were prepared from eleven different tissues of velvet ash and sequenced by using the Illumina genome analyzer. Subsequently, de novo assemebly, functional annotation databases, and the screening of expressed sequence tag-simple sequence repeats (EST-SSRs) were performed by comparing with corresponding databases using BLASTx and software tools. We obtained 51 698 unigenes with an average length of 661 bp and an N50 length of 980 bp. Among all these unigenes, 41 267 (79.8 %) were annotated in the NCBI non-redundant protein database and 25 236 (48.8 %) were annotated in the Swiss-Prot database. A total of 31 546 (61.0 %) and 13 281 (25.7 %) unigenes were successfully categorized to 59 and 25 functional groups, respectively, by gene ontology categories and clusters of orthologous group categories. A total of 22 323 (43.2 %) unigenes were assigned to 128 pathways using the Kyoto encyclopedia of genes and genomes pathway database. Additionally, 3 249 EST-SSRs markers were detected in 51 698 unigenes from velvet ash. Based on 3 249 EST-SSRs markers, 1 800 primer pairs were successfully designed using Primer 3. In the 50 randomly selected primers, 48 successfully amplified fragments, and 42 showed polymorphisms. We completed a successful application of the Illumina platform to de novo transcriptome assembly of velvet ash, which has the potential to be used for discovering novel genes and further characterization of gene expression profiles.

Wild rice genotypes are rich in genetic diversity. This has potential to improve agronomic rice by allele mining for superior traits. Late embryogenesis abundant (LEA) proteins are often associated with desiccation tolerance and stress signalling. In the present study, a group 3 LEA gene, Wsi18 from the wild rice Oryza nivara was expressed under its own inducible promoter element in stress susceptible cultivated indica rice (cv. IR20). The resulting transgenic plants cultivated in a greenhouse showed enhanced tolerance to soil water deficit. Transgenic plants had higher grain yield, plant survival rate, and shoot relative water content compared to wild type (WT) IR20. Cell membrane stability index, proline and soluble sugar content were also greater in transgenic than WT plants under water stress. These results demonstrate the potential for improving SWS tolerance in agronomically important rice cultivar by incorporating Wsi18 gene from a wild rice O. nivara.