Environmental stresses can significantly alter the synthesis of both primary and secondary metabo... more Environmental stresses can significantly alter the synthesis of both primary and secondary metabolites, resulting in medicinal plants with unpredictable biological activity. Here, in vitro shoot cultures of the medicinal plant Sutherlandia frutescens were used to study the impact of three abiotic stresses (nitrogen availability, drought and salinity), primarily on l-canavanine synthesis. This compound, a non-protein amino acid, is amongst those metabolites linked to the health benefits of Sutherlandia extracts. Nitrogen supplied to microplants positively correlated with canavanine levels, exhibited by a fourfold reduction when nitrates provided were halved. Although the biomass generated was lowered under these conditions, a higher capacity for rooting (52%) in comparison to the controls (37%) became evident. Only a small increase of the canavanine content in microplants growing on 100mM NaCl medium was detected, indicating that salinity stress was not a major limitation on cavanine production, but that it played more of a role in vitro on plantlet morphogenesis. Similarly, PEG as a supplement had little to no effect on canavanine synthesis. We conclude that a deeper understanding of the nutritional requirements for the agricultural crop management of S. frutescens, which serves the herbal products industry, is needed.
cDNA-AFLP is a commonly used, robust, and reproducible tool for genome-wide expression analysis i... more cDNA-AFLP is a commonly used, robust, and reproducible tool for genome-wide expression analysis in any species, without requirement of prior sequence knowledge. Quantitative expression data are generated by gel-based visualization of cDNA-AFLP fingerprints obtained by selective PCR amplification of subsets of restriction fragments from a double-stranded cDNA template. Differences in gene expression levels across the samples are reflected in different band intensities on the high-resolution polyacrylamide gels. The differentially expressed genes can be identified by direct sequencing of re-amplified cDNA-AFLP tags purified from the gels. The cDNA-AFLP technique is especially useful for profiling of transcriptional responses of jasmonate-treated plants or plant (tissue) cultures and the discovery of jasmonate-responsive genes.
Lateral organ boundary formation is highly regulated by transcription factors and hormones such a... more Lateral organ boundary formation is highly regulated by transcription factors and hormones such as auxins and brassinosteroids. However, in contrast to many other developmental processes in plants, no role for signalling peptides in the regulation of this process has been reported yet. The first characterization of the secreted cysteine-rich TAXIMIN (TAX) signalling peptides in Arabidopsis is presented here. TAX1 overexpression resulted in minor alterations in the primary shoot and root metabolome, abnormal fruit morphology, and fusion of the base of cauline leaves to stems forming a decurrent leaf attachment. The phenotypes at the paraclade junction match TAX1 promoter activity in this region and are similar to loss of LATERAL ORGAN FUSION (LOF) transcription factor function. Nevertheless, TAX1 expression was unchanged in lof1lof2 paraclade junctions and, conversely, LOF gene expression was unchanged in TAX1 overexpressing plants, suggesting TAX1 may act independently. This study i...
Environmental stresses can significantly alter the synthesis of both primary and secondary metabo... more Environmental stresses can significantly alter the synthesis of both primary and secondary metabolites, resulting in medicinal plants with unpredictable biological activity. Here, in vitro shoot cultures of the medicinal plant Sutherlandia frutescens were used to study the impact of three abiotic stresses (nitrogen availability, drought and salinity), primarily on l-canavanine synthesis. This compound, a non-protein amino acid, is amongst those metabolites linked to the health benefits of Sutherlandia extracts. Nitrogen supplied to microplants positively correlated with canavanine levels, exhibited by a fourfold reduction when nitrates provided were halved. Although the biomass generated was lowered under these conditions, a higher capacity for rooting (52%) in comparison to the controls (37%) became evident. Only a small increase of the canavanine content in microplants growing on 100mM NaCl medium was detected, indicating that salinity stress was not a major limitation on cavanine production, but that it played more of a role in vitro on plantlet morphogenesis. Similarly, PEG as a supplement had little to no effect on canavanine synthesis. We conclude that a deeper understanding of the nutritional requirements for the agricultural crop management of S. frutescens, which serves the herbal products industry, is needed.
Environmental stresses can significantly alter the synthesis of both primary and secondary metabo... more Environmental stresses can significantly alter the synthesis of both primary and secondary metabolites, resulting in medicinal plants with unpredictable biological activity. Here, in vitro shoot cultures of the medicinal plant Sutherlandia frutescens were used to study the impact of three abiotic stresses (nitrogen availability, drought and salinity), primarily on l-canavanine synthesis. This compound, a non-protein amino acid, is amongst those metabolites linked to the health benefits of Sutherlandia extracts. Nitrogen supplied to microplants positively correlated with canavanine levels, exhibited by a fourfold reduction when nitrates provided were halved. Although the biomass generated was lowered under these conditions, a higher capacity for rooting (52%) in comparison to the controls (37%) became evident. Only a small increase of the canavanine content in microplants growing on 100mM NaCl medium was detected, indicating that salinity stress was not a major limitation on cavanine production, but that it played more of a role in vitro on plantlet morphogenesis. Similarly, PEG as a supplement had little to no effect on canavanine synthesis. We conclude that a deeper understanding of the nutritional requirements for the agricultural crop management of S. frutescens, which serves the herbal products industry, is needed.
cDNA-AFLP is a commonly used, robust, and reproducible tool for genome-wide expression analysis i... more cDNA-AFLP is a commonly used, robust, and reproducible tool for genome-wide expression analysis in any species, without requirement of prior sequence knowledge. Quantitative expression data are generated by gel-based visualization of cDNA-AFLP fingerprints obtained by selective PCR amplification of subsets of restriction fragments from a double-stranded cDNA template. Differences in gene expression levels across the samples are reflected in different band intensities on the high-resolution polyacrylamide gels. The differentially expressed genes can be identified by direct sequencing of re-amplified cDNA-AFLP tags purified from the gels. The cDNA-AFLP technique is especially useful for profiling of transcriptional responses of jasmonate-treated plants or plant (tissue) cultures and the discovery of jasmonate-responsive genes.
Lateral organ boundary formation is highly regulated by transcription factors and hormones such a... more Lateral organ boundary formation is highly regulated by transcription factors and hormones such as auxins and brassinosteroids. However, in contrast to many other developmental processes in plants, no role for signalling peptides in the regulation of this process has been reported yet. The first characterization of the secreted cysteine-rich TAXIMIN (TAX) signalling peptides in Arabidopsis is presented here. TAX1 overexpression resulted in minor alterations in the primary shoot and root metabolome, abnormal fruit morphology, and fusion of the base of cauline leaves to stems forming a decurrent leaf attachment. The phenotypes at the paraclade junction match TAX1 promoter activity in this region and are similar to loss of LATERAL ORGAN FUSION (LOF) transcription factor function. Nevertheless, TAX1 expression was unchanged in lof1lof2 paraclade junctions and, conversely, LOF gene expression was unchanged in TAX1 overexpressing plants, suggesting TAX1 may act independently. This study i...
Environmental stresses can significantly alter the synthesis of both primary and secondary metabo... more Environmental stresses can significantly alter the synthesis of both primary and secondary metabolites, resulting in medicinal plants with unpredictable biological activity. Here, in vitro shoot cultures of the medicinal plant Sutherlandia frutescens were used to study the impact of three abiotic stresses (nitrogen availability, drought and salinity), primarily on l-canavanine synthesis. This compound, a non-protein amino acid, is amongst those metabolites linked to the health benefits of Sutherlandia extracts. Nitrogen supplied to microplants positively correlated with canavanine levels, exhibited by a fourfold reduction when nitrates provided were halved. Although the biomass generated was lowered under these conditions, a higher capacity for rooting (52%) in comparison to the controls (37%) became evident. Only a small increase of the canavanine content in microplants growing on 100mM NaCl medium was detected, indicating that salinity stress was not a major limitation on cavanine production, but that it played more of a role in vitro on plantlet morphogenesis. Similarly, PEG as a supplement had little to no effect on canavanine synthesis. We conclude that a deeper understanding of the nutritional requirements for the agricultural crop management of S. frutescens, which serves the herbal products industry, is needed.
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Papers by Janine Colling