Organogenic response of photomorphogenic mutants of tomato

The effect of white (WL) and red (RL) light on organogenesis in vitro was studied using explants isolated from seedlings of wild-type (WT) and two photo morphogenic mutants of tomato (Lycopersicon esculentum Mill.) - aurea (au) and high pigment (hp). Explants excised from hypocotyls and cotyledons of green and etiolated seedlings were cultured on shoot or root inducing media. It was observed that both continuous white (CWL) and red light (CRL) stimulate shoot formation on hypocotyl explants isolated from green seedlings ofWT and hp plants compared with control ones cultured in darkness. On the other hand, au mutant shows very low organogenetic response in spite of light conditions applied. Explants isolated from both green and etiolated seedlings were not able to form shoots when they were cultured in darkness. In contrast to green explants, etiolated ones formed roots in spite of being grown on a shoot inducing medium. Root regeneration from etiolated explants was stimulated by short, 5-min-long daily pulses of RL. This effect was reversed by subsequent far-red light (FRL) irradiation. Stimulation of shoot regeneration from etiolated explants was found when 2-h-long daily irradiation with WL or RL was applied. The highest and the lowest shoot regeneration response was obtained from hp and au explants, respectively, with an intermediate response from WT. Under the same growth conditions shoot formation was accompanied by root formation, which also occurred in a light dependent manner. The highest number of roots regenerated from au-derived explants. The results that we have obtained may suggest that shoot formation is strongly dependent on the light sensitivity of plants and light conditions applied. It also seems that the pattern of organ (shoot and root) development in tomato is affected by the etiolated/deetiolated phenotype of explant. Therefore, w

Reactive oxygen species localization in roots of Arabidopsis thaliana seedlings grown under phosphate deficiency

Arabidopsis plants responding to phosphorus (P) deficiency increase lateral root formation and reduce primary root elongation. In addition the number and length of root hairs increases in response to P deficiency. Here we studied the patterns of radical oxygen species (ROS) in the roots of Arabidopsis seedlings cultured on media supplemented with high or low P concentration. We found that P availability affected ROS distribution in the apical part of roots. If plants were grown on high P medium, ROS were located in the root elongation zone and quiescent centre. At low P ROS were absent in the elongation zone, however, their synthesis was detected in the primary root meristem. The proximal part of roots was characterized by ROS production in the lateral root primordia and in elongation zones of young lateral roots irrespective of P concentration in the medium. On the other hand, plants grown at high or low P differed in the pattern of ROS distribution in older lateral roots. At high P, the elongation zone was the primary site of ROS production. At low P, ROS were not detected in the elongation zone. However, they were present in the proximal part of the lateral root meristem. These results suggest that P deficiency affects ROS distribution in distal parts of Arabidopsis roots. Under P-sufficiency ROS maximum was observed in the elongation zone, under low P, ROS were not synthesized in this segment of the root, however, they were detected in the apical root meristem

Transcriptome profiling and environmental linkage to salinity across Salicornia europaea vegetation

Background: Salicornia europaea, a succulent obligatory halophyte is the most salt-tolerant plant species in the world. It survives salt concentrations of more than 1 M. Therefore, it is a suitable model plant to identify genes involved in salt tolerance mechanisms that can be used for the improvement of crops. The changes in a plant’s gene expression in response to abiotic stresses may depend on factors like soil conditions at the site, seasonality, etc. To date, experiments were performed to study the gene expression of S. europaea only under controlled conditions. Conversely, the present study investigates the transcriptome and physicochemical parameters of S. europaea shoots and roots from two different types of saline ecosystems growing under natural conditions. Results: The level of soil salinity was higher at the naturally saline site than at the anthropogenic saline site. The parameters such as ECe, Na+, Cl−, Ca+, SO4 2− and HCO3− of the soils and plant organs significantly varied according to sites and seasons. We found that Na+ mainly accumulated in shoots, whereas K+ and Ca2+ levels were higher in roots throughout the growing period. Moreover, changes in S. europaea gene expression were more prominent in seasons, than sites and plant organs. The 30 differentially expressed genes included enzymes for synthesis of Sadenosyl methionine, CP47 of light-harvesting complex II, photosystem I proteins, Hsp70 gene, ATP-dependent Clp proteases, ribulose bisphosphate carboxylase/oxygenase (Rubisco), phenylalanine ammonia-lyase (PAL), cytochrome c oxidase (COX) and ATP synthase. Conclusion: The comparisons made based on two seasons, plant organs and two different sites suggest the importance of seasonal variations in gene expression of S. europaea. We identify the genes that may play an important role in acclimation to season-dependent changes of salinity. The genes were involved in processes such as osmotic adjustment, energy metabolism and photosynthesis

Antioxidant Response in the Salt-Acclimated Red Beet (<i>Beta vulgaris</i>) Callus

Callus cultures initiated from red beet tubers were acclimated to 75 or 100 mM NaCl salinity by exposing them to gradually increasing NaCl concentrations. The acclimated callus lines displayed growth rates comparable to the control culture cultivated on the NaCl-free medium. Several antioxidant system components were analyzed to assess the role of the antioxidant defense in the acclimated callus’s ability to proliferate on salt-supplemented media. It was found that proline and ascorbate concentrations were increased in salt-acclimated callus lines with respect to the control line. On the other hand, glutathione concentration was unchanged in all tested callus lines. Total activities of the antioxidant enzymes, namely superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), ascorbate peroxidase (APX, EC 1.11.1.11), and class III peroxidase (POX, EC 1.11.1.7) were increased in salt-acclimated cultures. The enzymatic components of the antioxidant systems were upregulated in a coordinated manner during the initial phases of the culture cycle when the increase in callus fresh mass occurs

Role of Ascorbate in the Regulation of the Arabidopsis thaliana Root Growth by Phosphate Availability

Arabidopsis root system responds to phosphorus (P) deficiency by decreasing primary root elongation and developing abundant lateral roots. Feeding plants with ascorbic acid (ASC) stimulated primary root elongation in seedlings grown under limiting P concentration. However, at high P, ASC inhibited root growth. Seedlings of ascorbate-deficient mutant (vtc1) formed short roots irrespective of P availability. P-starved plants accumulated less ascorbate in primary root tips than those grown under high P. ASC-treatment stimulated cell divisions in root tips of seedlings grown at low P. At high P concentrations ASC decreased the number of mitotic cells in the root tips. The lateral root density in seedlings grown under P deficiency was decreased by ASC treatments. At high P, this parameter was not affected by ASC-supplementation. vtc1 mutant exhibited increased lateral root formation on either, P-deficient or P-sufficient medium. Irrespective of P availability, high ASC concentrations reduced density and growth of root hairs. These results suggest that ascorbate may participate in the regulation of primary root elongation at different phosphate availability via its effect on mitotic activity in the root tips

Characteristic of the Ascorbate Oxidase Gene Family in Beta vulgaris and Analysis of the Role of AAO in Response to Salinity and Drought in Beet

Ascorbate oxidase, which is known to play a key role in regulating the redox state in the apoplast, cell wall metabolism, cell expansion and abiotic stress response in plants, oxidizes apo-plastic ascorbic acid (AA) to dehydroascorbic acid (DHA). However, there is little information about the AAO genes and their functions in beets under abiotic stress. The term salt or drought stress refers to the treatment of plants with slow and gradual salinity/drought. Contrastingly, salt shock consists of exposing plants to high salt levels instantaneously and drought shock occurs under fast drought progression. In the present work, we have subjected plants to salinity or drought treatments to elicit either stress or shock and carried out a genome-wide analysis of ascorbate oxidase (AAO) genes in sugar beet (B. vulgaris cv. Huzar) and its halophytic ancestor (B. maritima). Here, conserved domain analyses showed the existence of twelve BvAAO gene family members in the genome of sugar beet. The BvAAO_1&ndash;12 genes are located on chromosomes 4, 5, 6, 8 and 9. The phylogenetic tree exhibited the close relationships between BvAAO_1-12 and AAO genes of Spinacia oleracea and Chenopodium quinoa. In both beet genotypes, downregulation of AAO gene expression with the duration of salt stress or drought treatment was observed. This correlated with a decrease in AAO enzyme activity under defined experimental setup. Under salinity, the key downregulated gene was BvAAO_10 in Beta maritima and under drought the BvAAO_3 gene in both beets. This phenomenon may be involved in determining the high tolerance of beet to salinity and drought

Salt stress and salt shock differently affect DNA methylation in salt-responsive genes in sugar beet and its wild, halophytic ancestor.

Here we determined the impact of salt shock and salt stress on the level of DNA methylation in selected CpG islands localized in promoters or first exons of sixteen salt-responsive genes in beets. Two subspecies differing in salt tolerance were subjected for analysis, a moderately salt-tolerant sugar beet Beta vulgaris ssp. vulgaris cv. Huzar and a halophytic beet, Beta vulgaris ssp. maritima. The CpG island methylation status was determined. All target sequences were hyper- or hypomethylated under salt shock and/or salt stress in one or both beet subspecies. It was revealed that the genomic regions analyzed were highly methylated in both, the salt treated plants and untreated controls. Methylation of the target sequences changed in a salt-dependent manner, being affected by either one or both treatments. Under both shock and stress, the hypomethylation was a predominant response in sugar beet. In Beta vulgaris ssp. maritima, the hypermethylation occurred with higher frequency than hypomethylation, especially under salt stress and in the promoter-located CpG sites. Conversely, the hypomethylation of the promoter-located CpG sites predominated in sugar beet plants subjected to salt stress. This findings suggest that DNA methylation may be involved in salt-tolerance and transcriptomic response to salinity in beets

Modeling of phytoextraction efficiency of microbially stimulated <i>Salix dasyclados</i> L. in the soils with different speciation of heavy metals

<p>Bioaugmentation of soils with selected microorganisms during phytoextraction can be the key solution for successful bioremediation and should be accurately calculated for different physicochemical soil properties and heavy metal availability to guarantee the universality of this method. Equally important is the development of an accurate prediction tool to manage phytoremediation process. The main objective of this study was to evaluate the role of three metallotolerant siderophore-producing <i>Streptomyces</i> sp. B1–B3 strains in the phytoremediation of heavy metals with the use of <i>S. dasyclados</i> L. growing in four metalliferrous soils as well as modeling the efficiency of this process based on physicochemical and microbiological properties of the soils using artificial neural network (ANN) analysis. The bacterial inoculation of plants significantly stimulated plant biomass and reduced oxidative stress. Moreover, the bacteria affected the speciation of heavy metals and finally their mobility, thereby enhancing the uptake and bioaccumulation of Zn, Cd, and Pb in the biomass. The best capacity for phytoextraction was noted for strain B1, which had the highest siderophore secretion ability. Finally, ANN model permitted to predict efficiency of phytoextraction based on both the physicochemical properties of the soils and the activity of the soil microbiota with high precision.</p