Project description:Drought stress response is a complex trait regulated at multiple levels. In the past few years, molecular and genomic studies have shown that several drought responsive genes (DRGs) with various functions are induced by drought stresses, and that various transcription factors (TFs) are involved in the regulation of stress-inducible genes. In addition to those DRGs mentioned above, microRNAs (miRNAs) are important regulators of gene expression at the posttranscriptional level by repressing mRNA expression. There is a complex interplay between transcriptional and post-transcriptional regulation of drought response that has not been extensively characterized in tobacco. In order to fully understand DRGs (including TFs) and different roles of miRNAs involved in the stress response, we sequenced and analysed three Digital Gene Expression (DGE) libraries in roots from drought treated tobacco plants, and four small RNA populations in roots, stems and leaves from control or drought treated tobacco plants. We identified 276 candidate DRGs in tobacco with sequence similarities to 64 known DRGs from model plants and crops and about 40% were TFs including WRKY, NAC, ERF and bZIP families. Furthermore, Out of these tobacco DRGs, 54differentially expressed DRGs included 21 TFs, which belonged to 24 TFs families such as NAC (6), MYB (4), ERF (10) and bZIP (1). Additionally, we confirmed expression of 39 known miRNA families (122 members) and five conserved miRNA families, which showed differential regulation under drought stress. Targets of miRNAs were further surveyed based on a recently published study, in which ten targets were DRGs. Finally, an integrated gene regulatory network has been proposed for the molecular mechanisms of the response of tobacco roots to drought stress using differentially expressed DRGs, the changed expression proﬁles of miRNAs and their target transcripts as a basis base on previous studies. In general, our data provide valuable information for future studies of the molecular mechanisms underlying tobacco roots in response to drought resistance in tobacco and other plants.

Project description:Drought stress response is a complex trait regulated at multiple levels. In the past few years, molecular and genomic studies have shown that several drought responsive genes (DRGs) with various functions are induced by drought stresses, and that various transcription factors (TFs) are involved in the regulation of stress-inducible genes. In addition to those DRGs mentioned above, microRNAs (miRNAs) are important regulators of gene expression at the posttranscriptional level by repressing mRNA expression. There is a complex interplay between transcriptional and post-transcriptional regulation of drought response that has not been extensively characterized in tobacco. In order to fully understand DRGs (including TFs) and different roles of miRNAs involved in the stress response, we sequenced and analysed three Digital Gene Expression (DGE) libraries in roots from drought treated tobacco plants, and four small RNA populations in roots, stems and leaves from control or drought treated tobacco plants. We identified 276 candidate DRGs in tobacco with sequence similarities to 64 known DRGs from model plants and crops and about 40% were TFs including WRKY, NAC, ERF and bZIP families. Furthermore, Out of these tobacco DRGs, 54differentially expressed DRGs included 21 TFs, which belonged to 24 TFs families such as NAC (6), MYB (4), ERF (10) and bZIP (1). Additionally, we confirmed expression of 39 known miRNA families (122 members) and five conserved miRNA families, which showed differential regulation under drought stress. Targets of miRNAs were further surveyed based on a recently published study, in which ten targets were DRGs. Finally, an integrated gene regulatory network has been proposed for the molecular mechanisms of the response of tobacco roots to drought stress using differentially expressed DRGs, the changed expression proﬁles of miRNAs and their target transcripts as a basis base on previous studies. In general, our data provide valuable information for future studies of the molecular mechanisms underlying tobacco roots in response to drought resistance in tobacco and other plants. Three tobacco (Nicotiana tabacum L.) roots tag-based DGE libraries treated at three time points (0, 6 and 48 h) with 20% PEG6000 were generated using Illumina 1G technology. The samples for four small RNA libraries was used based on the result of physiological index measurement as follows: equal quantities (10 ug) of total RNA isolated from tobacco roots treated with two time points (6 and 48 h) were mixed together to construct the drought -treated small RNA library (Root-treat), and total RNA prepared from the control roots sample was used to construct the control small RNA library (Root-ck). In addition, we also constructed another two libraries (stem and leaf) from leaves and stems of control plants, respectively. These libraries were constructed using the Small RNA Sample Prep Kit (Illumina, San Diego, CA) and then sent for Solexa sequencing.

Project description:Bacillus thuringiensis, a well-known and effective bio-insecticide, has attracted considerable attention as a potential biological control agent for the suppression of plant diseases. Treatment of tomato roots with a filter-sterilized cell-free filtrate (CF) of B. thuringiensis systemically suppresses bacterial wilt caused by Ralstonia solanacearum through systemic activation of the plant defense system. Comparative analysis of the expression of the Pathogenesis-Related 1(P6) [PR-1(P6)] gene, a marker for induced resistance to pathogens, in various tissues of tomato plants treated with CF on their roots suggested that the B. thuringiensis-induced defense system was activated in the leaf, stem, and main root tissues, but not in the lateral root tissue. At the same time, the growth of R. solanacearum was significantly suppressed in the CF-treated main root tissue but not in the CF-treated lateral root tissue. This distinct activation of the defense reaction and suppression of R. solanacearum were reflected by the differences in the transcriptional profiles of the main and lateral tissues in response to the CF. In the CF-treated main root tissue, but not CF-treated lateral root tissue, the expression of several salicylic acid (SA)-responsive defense-related genes was specifically induced, whereas jasmonic acid (JA)-related gene expression was either down-regulated or not induced in response to the CF. On the other hand, genes encoding ethylene (ET)-related proteins were induced equally in both the main and lateral root tissues. Taken together, the co-activation of SA-dependent signaling pathway with ET-dependent signaling pathway and suppression of JA-dependent signaling pathway may play key roles in B. thuringiensis-induced resistance to R. solanacearum in tomato plants. Gene expression was measured in main and lateral root tissues of tomato treated with Bacillus thuringiensis or distilled water-treated control at 48 hours after treatment. Two independent experiments were performed at each tissue (main root or lateral root tissue) for each treatment (Bacillus thuringiensis or distilled water control).

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Identification of natural diterpenes as inducers of resistance to bacterial wilt disease in tobacco, tomato, and Arabidopsis

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