Project description:Jatropha curcas L. is a potential biofuel plant. Application of exogenous cytokinin (6-benzyladenine, BA) on its inflorescence buds can significantly increase the number of female flowers, thereby improving seed yield. To investigate which genes and signal pathways are involved in the response to cytokinin in J. curcas inflorescence buds, we monitored transcriptional activity in inflorescences at 0, 3, 12, 24, and 48 h after BA treatment using a microarray. We detected 5,555 differentially expressed transcripts over the course of the experiment, which could be grouped into 12 distinct temporal expression patterns. We also identified 31 and 131 transcripts in J. curcas whose homologs in model plants function in flowering and phytohormonal signaling pathways, respectively. According to the transcriptional analysis of genes involved in flower development, we hypothesized that BA treatment delays floral organ formation by inhibiting the transcription of the A, B and E classes of floral organ-identity genes, which would allow more time to generate more floral primordia in inflorescence meristems, thereby enhancing inflorescence branching and significantly increasing flower number per inflorescence. BA treatment might also play an important role in maintaining the flowering signals by activating the transcription of GIGANTEA (GI) and inactivating the transcription of CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1) and TERMINAL FLOWER 1b (TFL1b). In addition, exogenous cytokinin treatment could regulate the expression of genes involved in the metabolism and signaling of other phytohormones, indicating that cytokinin and other phytohormones jointly regulate flower development in J. curcas inflorescence buds. Our study provides a framework to better understand the molecular mechanisms underlying changes in flowering traits in response to cytokinin treatment in J. curcas inflorescence buds. The results provide valuable information related to the mechanisms of cross-talk among multiple phytohormone signaling pathways in woody plants.
Project description:Jatropha curcas L. is a potential biofuel plant. Application of exogenous cytokinin (6-benzyladenine, BA) on its inflorescence buds can significantly increase the number of female flowers, thereby improving seed yield. To investigate which genes and signal pathways are involved in the response to cytokinin in J. curcas inflorescence buds, we monitored transcriptional activity in inflorescences at 0, 3, 12, 24, and 48 h after BA treatment using a microarray. We detected 5,555 differentially expressed transcripts over the course of the experiment, which could be grouped into 12 distinct temporal expression patterns. We also identified 31 and 131 transcripts in J. curcas whose homologs in model plants function in flowering and phytohormonal signaling pathways, respectively. According to the transcriptional analysis of genes involved in flower development, we hypothesized that BA treatment delays floral organ formation by inhibiting the transcription of the A, B and E classes of floral organ-identity genes, which would allow more time to generate more floral primordia in inflorescence meristems, thereby enhancing inflorescence branching and significantly increasing flower number per inflorescence. BA treatment might also play an important role in maintaining the flowering signals by activating the transcription of GIGANTEA (GI) and inactivating the transcription of CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1) and TERMINAL FLOWER 1b (TFL1b). In addition, exogenous cytokinin treatment could regulate the expression of genes involved in the metabolism and signaling of other phytohormones, indicating that cytokinin and other phytohormones jointly regulate flower development in J. curcas inflorescence buds. Our study provides a framework to better understand the molecular mechanisms underlying changes in flowering traits in response to cytokinin treatment in J. curcas inflorescence buds. The results provide valuable information related to the mechanisms of cross-talk among multiple phytohormone signaling pathways in woody plants. Gene expression of flower buds in response to BA was measured at 0h, 3h, 12h, 24h and 48h after 1mM 6-benzylaminopurine treatment. Three biological replicates were prepared for each time point.
Project description:Jatropha curcas, a multipurpose plant attracting much attention due to its high oil content and quality for biofuel, is recognized as a drought tolerant species. However, this drought tolerance is still poorly characterized. This study aims to contribute to uncover the molecular background of this tolerance, with the use of a combined approach of transcriptional profiling and morphophysiological characterization along a period of water withholding (49 days) followed by rewatering (7 days). Morphophysiological measurements evidenced that J. curcas plants presented different adaptations to withstand moderate and severe drought. Thus, RNA-Seq was performed for samples collected at moderate and severe stress followed by rewatering, for both roots and leaves. Transcriptomic analysis revealed organ-specific adaptations across all investigated conditions, except under severe stress, in which the drought response of J. curcas surpassed organ-specificity by dramatic transcriptomic reorganization. These changes in gene expression were clearly evidenced by the down-regulation of genes involved in growth and water uptake, and up-regulation of osmotic adjustments and cellular homeostasis related genes. However, organ-specific variations were also detected, such as strong up-regulation of chlorophyll and trehalose metabolism in leaves. Functional validation further corroborated the differentially expression of genes coding for enzymes involved in chlorophyll metabolism, which correlates with the metabolite content of this pathway. Two Jatropha curcas accessions were submitted to moderate and severe drought stress (water withholding) followed by recovery (3d re-watering), transcriptomic profiles were assessed by RNA-Seq.
Project description:Jatropha curcas, a multipurpose plant attracting much attention due to its high oil content and quality for biofuel, is recognized as a drought tolerant species. However, this drought tolerance is still poorly characterized. This study aims to contribute to uncover the molecular background of this tolerance, with the use of a combined approach of transcriptional profiling and morphophysiological characterization along a period of water withholding (49 days) followed by rewatering (7 days). Morphophysiological measurements evidenced that J. curcas plants presented different adaptations to withstand moderate and severe drought. Thus, RNA-Seq was performed for samples collected at moderate and severe stress followed by rewatering, for both roots and leaves. Transcriptomic analysis revealed organ-specific adaptations across all investigated conditions, except under severe stress, in which the drought response of J. curcas surpassed organ-specificity by dramatic transcriptomic reorganization. These changes in gene expression were clearly evidenced by the down-regulation of genes involved in growth and water uptake, and up-regulation of osmotic adjustments and cellular homeostasis related genes. However, organ-specific variations were also detected, such as strong up-regulation of chlorophyll and trehalose metabolism in leaves. Functional validation further corroborated the differentially expression of genes coding for enzymes involved in chlorophyll metabolism, which correlates with the metabolite content of this pathway.
Project description:Casbene synthase is responsible for the first commited step in the biosynthesis of phorbol esters (PE) in the Euphorbiaceae. PE are abundant in the seeds of the biofuel crop Jatropha curcas and its toxicity precludes the use of the protein-rich cake obtained after oil extraction as an animal feed and the toxicity of the fumes derived from burning PE containing biofuel is also a matter of concern. This toxicity is a major hindrance to exploit the potential of this crop as a source of raw material for the production of biodiesel. For this reason, current research on J. curcas is mainly focused in the understanding of the biosynthesis and site of synthesis of PE, as an avenue for the development of biotechnological of genotypes unable to synthesize PE in its seeds. Here, we present the results of targeted proteome assays (SRM and PRM) to monitor and quantify casbene synthase in leaves, endosperma and roots of two J. curcas of contrasting levels of PE. The assays were based in the use of synthetic isotopic labeled peptides derived from 12 gene models of casbene synthase from the J. curcas genome and results showed the presence of casbene synthase encoded in seven of the 12 gene models. Several specific transitions were identified and which can be used to monitor several casbene synthase proteins by any one of the two targeted proteomics assays and/or to validate the results of transcription-based experiments.