We recently demonstrated that microRNA399 (miR399) controls inorganic phosphate (Pi) homeostasis by regulating the expression of UBC24 encoding a ubiquitin-conjugating E2 enzyme in Arabidopsis ...(Arabidopsis thaliana). Transgenic plants overexpressing miR399 accumulated excessive Pi in the shoots and displayed Pi toxic symptoms. In this study, we revealed that a previously identified Pi overaccumulator, pho2, is caused by a single nucleotide mutation resulting in early termination within the UBC24 gene. The level of full-length UBC24 mRNA was reduced and no UBC24 protein was detected in the pho2 mutant, whereas up-regulation of miR399 by Pi deficiency was not affected. Several characteristics of Pi toxicity in the pho2 mutant were similar to those in the miR399-overexpressing and UBC24 T-DNA knockout plants: both Pi uptake and translocation of Pi from roots to shoots increased and Pi remobilization within leaves was impaired. These phenotypes of the pho2 mutation could be rescued by introduction of a wild-type copy of UBC24. Kinetic analyses revealed that greater Pi uptake in the pho2 and miR399-overexpressing plants is due to increased Vmax. The transcript level of most PHT1 Pi transporter genes was not significantly altered, except PHT1;8 whose expression was enhanced in Pi-sufficient roots of pho2 and miR399-overexpressing compared with wild-type plants. In addition, changes in the expression of several organelle-specific Pi transporters were noticed, which may be associated with the redistribution of intracellular Pi under excess Pi. Furthermore, miR399 and UBC24 were colocalized in the vascular cylinder. This observation not only provides important insight into the interaction between miR399 and UBC24 mRNA, but also supports their systemic function in Pi translocation and remobilization.
In this study, we reveal a mechanism by which plants regulate inorganic phosphate (Pi) homeostasis to adapt to environmental changes in Pi availability. This mechanism involves the suppression of a ...ubiquitin-conjugating E2 enzyme by a specific microRNA, miR399. Upon Pi starvation, the miR399 is upregulated and its target gene, a ubiquitin-conjugating E2 enzyme, is downregulated in Arabidopsis thaliana. Accumulation of the E2 transcript is suppressed in transgenic Arabidopsis overexpressing miR399. Transgenic plants accumulated five to six times the normal Pi level in shoots and displayed Pi toxicity symptoms that were phenocopied by a loss-of-function E2 mutant. Pi toxicity was caused by increased Pi uptake and by translocation of Pi from roots to shoots and retention of Pi in the shoots. Moreover, unlike wild-type plants, in which Pi in old leaves was readily retranslocated to other developing young tissues, remobilization of Pi in miR399-overexpressing plants was impaired. These results provide evidence that miRNA controls Pi homeostasis by regulating the expression of a component of the proteolysis machinery in plants.
In this study, we reveal a mechanism by which plants regulate inorganic phosphate (Pi) homeostasis to adapt to environmental changes in Pi availability. This mechanism involves the suppression of a ...ubiquitin-conjugating E2 enzyme by a specific microRNA, miR399. Upon Pi starvation, the miR399 is upregulated and its target gene, a ubiquitin-conjugating E2 enzyme, is downregulated in
Arabidopsis thaliana
. Accumulation of the E2 transcript is suppressed in transgenic
Arabidopsis
overexpressing miR399. Transgenic plants accumulated five to six times the normal Pi level in shoots and displayed Pi toxicity symptoms that were phenocopied by a loss-of-function E2 mutant. Pi toxicity was caused by increased Pi uptake and by translocation of Pi from roots to shoots and retention of Pi in the shoots. Moreover, unlike wild-type plants, in which Pi in old leaves was readily retranslocated to other developing young tissues, remobilization of Pi in miR399-overexpressing plants was impaired. These results provide evidence that miRNA controls Pi homeostasis by regulating the expression of a component of the proteolysis machinery in plants.
We recently demonstrated that microRNA399 (miR399) controls inorganic phosphate (Pi) homeostasis by regulating the expression of UBC24 encoding a ubiquitin-conjugating E2 enzyme in Arabidopsis ...(Arabidopsis thaliana). Transgenic plants overexpressing miR399 accumulated excessive Pi in the shoots and displayed Pi toxic symptoms. In this study, we revealed that a previously identified Pi overaccumulator, pho2, is caused by a single nucleotide mutation resulting in early termination within the UBC24 gene. The level of full-length UBC24 mRNA was reduced and no UBC24 protein was detected in the pho2 mutant, whereas up-regulation of miR399 by Pi deficiency was not affected. Several characteristics of Pi toxicity in the pho2 mutant were similar to those in the miR399-overexpressing and UBC24 T-DNA knockout plants: both Pi uptake and translocation of Pi from roots to shoots increased and Pi remobilization within leaves was impaired. These phenotypes of the pho2 mutation could be rescued by introduction of a wild-type copy of UBC24. Kinetic analyses revealed that greater Pi uptake in the pho2 and miR399-overexpressing plants is due to increased Vmax. The transcript level of most PHT1 Pi transporter genes was not significantly altered, except PHT1;8 whose expression was enhanced in Pi-sufficient roots of pho2 and miR399-overexpressing compared with wild-type plants. In addition, changes in the expression of several organelle-specific Pi transporters were noticed, which may be associated with the redistribution of intracellular Pi under excess Pi. Furthermore, miR399 and UBC24 were colocalized in the vascular cylinder. This observation not only provides important insight into the interaction between miR399 and UBC24 mRNA, but also supports their systemic function in Pi translocation and remobilization.
碩士
國立政治大學
科技管理與智慧財產研究所
104
An enterprise in the process of sustainable management, facing the constant pursuit of growth and change of market demand, and due to changes in the environment, regarding ...the enterprise whether caused by internal and external impact, will force firms to transformation.
This study belongs in the medical cosmetic industry in case study of the company, how to through an agent by the consumable medical device product, to study for transformation of the enterprise case. Focus on enterprises in the pursuit of sustained growth in the process. How to through knowledge management, innovation ability and strategic formulation to develop the new markets? And, to reconfigure and effectively use for its limited resources, and by through a series of activities to accumulate their own core competencies. The case study of the company entered a not belong to the company's existing scope of business activities, and to carry out a new business.
The conclusions of this research are:
1. The knowledge m
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