BACKGROUND: Cytokinin is a negative regulator of root growth, and a reduction of the cytokinin content or signalling causes the formation a larger root system in model plants, improves their growth under drought and nutrient limitation and causes increased accumulation of elements in the shoot. Roots are an important but understudied target of plant breeding. Here we have therefore explored whether root enhancement by lowering the cytokinin content can also be achieved in oilseed rape (Brassica napus L.) plants. RESULTS: Transgenic plants overexpressing the CKX2 gene of Arabidopsis thaliana encoding a cytokinin-degrading cytokinin oxidase/dehydrogenase showed higher CKX activity and a strongly reduced cytokinin content. Cytokinin deficiency led to the formation of a larger root system under different growth conditions, which was mainly due to an increased number of lateral and adventitious roots. In contrast, shoot growth was comparable to wild type, which caused an enhanced root-to-shoot ratio. Transgenic plants accumulated in their leaves higher concentrations of macro- and microelements including P, Ca, Mg, S, Zn, Cu, Mo and Mn. They formed more chlorophyll under Mg- and S-deficiency and accumulated a larger amount of Cd and Zn from contaminated medium and soil. CONCLUSIONS: These findings demonstrate the usefulness of ectopic CKX gene expression to achieve root enhancement in oilseed rape and underpin the functional relevance of a larger root system. Furthermore, the lack of major developmental consequences on shoot growth in cytokinin-deficient oilseed rape indicates species-specific differences of CKX gene and/or cytokinin action.

• Keywords
• Brassica napus, Cytokinin, Cytokinin oxidase/dehydrogenase, Leaf mineral enrichment, Phytoremediation, Plant growth, Root enhancement,
• MeSH
• Biodegradation, Environmental * MeSH
• Brassica napus genetics   growth & development   metabolism   MeSH
• Chlorophyll analysis   metabolism   MeSH
• Cytokinins genetics   metabolism   MeSH
• Plants, Genetically Modified MeSH
• Cadmium analysis   metabolism   MeSH
• Plant Roots growth & development   metabolism   MeSH
• Plant Leaves chemistry   metabolism   MeSH
• Oxidoreductases genetics   metabolism   MeSH
• Soil chemistry   MeSH
• Zinc analysis   metabolism   MeSH
• Nutrients analysis   metabolism   MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Chlorophyll MeSH
• cytokinin oxidase MeSH Browser
• Cytokinins MeSH
• Cadmium MeSH
• Oxidoreductases MeSH
• Soil MeSH
• Zinc MeSH