Polyamines （PA）, polyamine oxidases, copper amine oxidases, and nitric oxide （NO） play important roles in physiology and stress responses in plants. NO biosynthesis as a result of catabolism of PA by polyamine oxi...Polyamines （PA）, polyamine oxidases, copper amine oxidases, and nitric oxide （NO） play important roles in physiology and stress responses in plants. NO biosynthesis as a result of catabolism of PA by polyamine oxidases and copper amine oxidases may explain in part PA-mediated responses. Involvement of a copper amine oxidase gene, COPPER AMINE OXIDASEI （CuAO1）, of Arabidopsis was tested for its role in stress responses using the knockouts cuao1-1 and cuaol-2. PA-induced and ABA-induced NO production investigated bY fluorometry and fluorescence microscopy showed that the cuaol-1 and cuaol-2 are impaired in NO production, suggesting a function of CuAO1 in PA and ABA-mediated NO production. Furthermore, we found a PA-dependent increase in protein S-nitrosylation. The addition of PA and ABA also resulted in H2O2 increases, cuao1-1 and cuao1-2 showed less sensitivity to exogenous ABA supplementation during germination, seedling establishment, and root growth inhibition as compared to wild-type. In response to ABA treatment, expression levels of the stress-responsive genes RD29A and ADH1 were significantly lower in the knockouts. These observations characterize cuao1-1 and cuao1-2 as ABA-insensitive mutants. Taken together, our findings extend the ABA signal transduction network to include CuAO1 as one potential contributor to enhanced NO production by ABA.展开更多
Besides providing protection against mechanical damage to the root tip, the root cap is involved in the perception and processing of diverse external and internal stimuli resulting in altered growth and development, T...Besides providing protection against mechanical damage to the root tip, the root cap is involved in the perception and processing of diverse external and internal stimuli resulting in altered growth and development, The transduction of these stimuli includes hormonal signaling pathways such as those of auxin, ethylene and cytokinin. Here, we show that the root cap is essential for the ethylene-induced regulation of elongation growth and root hair formation in maize. Exogenously applied ethylene is no longer able to inhibit elongation growth when the root cap has been surgically removed prior to hormone treatment. Reconstitution of the cap positively correlates with the developing capacity of the roots to respond to ethylene again. In contrast, the removal of the root cap does not per se affect growth inhibition controlled by auxin and cytokinin. Furthermore, our semi-quantitative RT-PCR results support earlier findings that the maize root cap is a site of high gene expression activity with respect to sensing and responding to hormones such as ethylene, From these data, we propose a novel function of the root cap which is the establishment of competence to respond to ethylene in the distal zones of the root.展开更多
文摘Polyamines （PA）, polyamine oxidases, copper amine oxidases, and nitric oxide （NO） play important roles in physiology and stress responses in plants. NO biosynthesis as a result of catabolism of PA by polyamine oxidases and copper amine oxidases may explain in part PA-mediated responses. Involvement of a copper amine oxidase gene, COPPER AMINE OXIDASEI （CuAO1）, of Arabidopsis was tested for its role in stress responses using the knockouts cuao1-1 and cuaol-2. PA-induced and ABA-induced NO production investigated bY fluorometry and fluorescence microscopy showed that the cuaol-1 and cuaol-2 are impaired in NO production, suggesting a function of CuAO1 in PA and ABA-mediated NO production. Furthermore, we found a PA-dependent increase in protein S-nitrosylation. The addition of PA and ABA also resulted in H2O2 increases, cuao1-1 and cuao1-2 showed less sensitivity to exogenous ABA supplementation during germination, seedling establishment, and root growth inhibition as compared to wild-type. In response to ABA treatment, expression levels of the stress-responsive genes RD29A and ADH1 were significantly lower in the knockouts. These observations characterize cuao1-1 and cuao1-2 as ABA-insensitive mutants. Taken together, our findings extend the ABA signal transduction network to include CuAO1 as one potential contributor to enhanced NO production by ABA.
文摘Besides providing protection against mechanical damage to the root tip, the root cap is involved in the perception and processing of diverse external and internal stimuli resulting in altered growth and development, The transduction of these stimuli includes hormonal signaling pathways such as those of auxin, ethylene and cytokinin. Here, we show that the root cap is essential for the ethylene-induced regulation of elongation growth and root hair formation in maize. Exogenously applied ethylene is no longer able to inhibit elongation growth when the root cap has been surgically removed prior to hormone treatment. Reconstitution of the cap positively correlates with the developing capacity of the roots to respond to ethylene again. In contrast, the removal of the root cap does not per se affect growth inhibition controlled by auxin and cytokinin. Furthermore, our semi-quantitative RT-PCR results support earlier findings that the maize root cap is a site of high gene expression activity with respect to sensing and responding to hormones such as ethylene, From these data, we propose a novel function of the root cap which is the establishment of competence to respond to ethylene in the distal zones of the root.
