The objective of this study was to investigate the effect of Selenium (Se) supply (0, 3, 6, 12, 24 mg kg−1) on the growth, photosynthetic characteristics, Se accumulation and distribution of flue-cured tobacco (Nicotiana tabacum L.). Results showed that low-dose Se treatments (≤6 mg kg−1) stimulated plant growth but high-dose Se treatments (≥12 mg kg−1) hindered plant growth. Optimal Se dose (6 mg kg−1) stimulated plant growth by reducing MDA content and improving photosynthetic capability. However, excess Se (24 mg kg−1) increased MDA content by 28%, decreased net photosynthetic rate and carboxylation efficiency by 34% and 39%, respectively. The Se concentration in the roots, stems, and leaves of the tobacco plants significantly increased with increasing Se application. A linear correlation (R = 0.95, P < 0.01) was observed between Se level and tobacco plant tissue Se concentration. This correlation indicated that the tobacco plant tissues were not saturated within the concentration range tested. The pattern of total Se concentration in the tobacco plant tissues followed the order root > leaf > stem. The Se concentration in the roots was 3.17 and 7.57 times higher than that in the leaves and stems, respectively, after treatment with 24 mg kg−1 Se. In conclusion, the present study suggested that optimal Se dose (6 mg kg−1) improved the plant growth mainly by enhancing photosynthesis, stomatal conductance, carboxylation efficiency and Rubisco content in the flue-cured tobacco leaves. However, the inhibition of excess Se on tobacco growth might be due to high accumulation of Se in roots and the damage of photosynthesis in leaves.
The tuber necrotic strain of Potato virus Y (PVYNTN) causes widespread disease and has severe negative effects on the growth and yields of plants, especially those of the Solanaceae family. The consequences of residual toxicity and non-biodegradation of synthetic chemicals and pollution of the environment has led to investigations into new non-toxic and biological treatments to control plant viral diseases. Ethanolic extracts of Bowiea volubilis (bulbs), Cotyledon orbiculata (leaves), Gomphocarpus fruticosus (leaves), Merwilla plumbea (dry and fresh bulbs), Nerium oleander (leaves), and the fruits and leaves of Strophanthus speciosus, were evaluated against PVYNTN in vivo and in vitro. At a concentration of 20 mg · ml−1, ethanolic extracts of Strophanthus speciosus (leaves) and fruits (50 mg · ml−1) significantly reduced the expression of PVYNTN symptoms on tobacco plants in vitro without affecting the normal growth and development of the plant. Similarly, at 50 mg · ml−1, N. oleander, C. orbiculata and B. volubilis (fresh bulbs) and S. speciousus leaves at 20 mg · ml−1 extracts showed significant differences in PVYNTN symptoms in the in vivo experiment. Strophanthus speciosus leaf and fruit extracts showed significant inhibition in the in vitro and in vivo assays and demonstrated that S. speciosus has potential to be used as an antiphytoviral treatment.
H. pylori ureA and ureB genes encoding both subunits of urease were expressed transgenically in a low-alkaloid line of tobacco (LA Burley 21). Analysis of transgene expression at both the mRNA and protein levels revealed a significant increase (up to 8-fold) in ammonia concentration correlated with an amount of UreB protein detected in the leaves, and an increase (up to 2-fold) in urease activity in transformants as compared to control plants.
Matrix attachment regions (MARs) are thought to participate in the organization and segregation of independent chromosomal loop domains. Although there are several reports on the action of natural MARs in the context of heterologous genes in transgenic plants, in our study we tested a synthetic MAR (sMAR) with the special property of unpairing when under superhelical strain, for its effect on reporter gene expression in tobacco plants. The synthetic MAR was a multimer of a short sequence from the MAR 3 end of the immunoglobulin heavy chain (IgH) enhancer. This sMAR sequence was used to flank the β-glucuronidase (GUS) reporter gene within the T-DNA of the binary vector pBI121. Vectors with or without the sMARs were then used to transform tobacco plants by Agrobacterium tumefaciens. Transgenic plants containing the sMAR sequences flanking the GUS gene exhibited higher levels of transgene expression compared with transgenic plants which lacked the sMARs. This effect was observed independently of the position of the sMAR at the 5 side of the reporter gene. However, variation of the detected transgene expression was significant in all transformed plant populations, irrespective of the construct used.
PR-10 proteins (pathogensis-related), ubiquitous within the plant kingdom, are usually encoded by multigene families. To date we have identified 10 homologous pr-10 genes in a yellow lupine cDNA library. Here, the structure and expression of two newly identified yellow lupine pr-10 genes (LlYpr10-2b and LlYpr10-2f) are presented. Many potential regulatory sites were found in both gene promoters including common ones as well as those unique for each gene. However, promoter deletion analysis in transgenic tobacco plants revealed similar patterns of reporter gene (gus) expression. Shortened fragments of both gene promoters studied caused high GUS activity in leaves (along vascular bundles), stamen stigma, anthers and pollen grains. When conjugated with longer LlYpr-10.2 promoter fragments, GUS was additionally present in petal edges. Only a long fragment of the LlYpr10-2b gene promoter caused GUS expression in the stem. In yellow lupine the pr-10.2 genes are present in all studied organs, but their level of expression depends on the stage of development and is affected by wounding, oxidative stress and salicylic acid treatment. Silencing of the Llpr-10.2b gene in 4-week-old yellow lupine plants did not lead to any visible symptoms, which suggests that the function of the silenced gene is supplemented by its close homologues, still present in the studied plants.
The role of histone H1 in the regulation of flower growth and development and in microsporogenesis was investigated in previously obtained transgenic tobacco plants expressing the antisense histone H1 cDNA. These plants exhibited a characteristic male-sterility phenotype caused by altered proportions of the native histone H1 in chromatin. The type and frequency of chromosomal aberrations during male meiosis as well as the distortions affecting tetrad formation in transgenic plants are reported.
Conditions of achieving the maximal accumulation of sulfhydryl metabolites in the leaves of tobacco were explored. Simultaneous production of bacterial O-acetylserine (thiol)-lyase and serine acetyltransferase resulted in the increased thiols contents as compared to single transformants and controls. However, leaf discs feeding experiments differently affected thiols concentration in different plant groups and suggested that the most promising strategy to obtain plants with a high level of non-protein thiol-containing compounds might be sulfate feeding to plants overproducing serine acetyltransferase.
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