pho2, a phosphate overaccumulator, is caused by a nonsense mutation in a MicroRNA399 target gene
pho2, a phosphate overaccumulator, is caused by a nonsense mutation in a MicroRNA399 target gene
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DOI：
10.1104/pp.106.078063
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发表时间：
2006-07-01
期刊：
影响因子：
7.4
通讯作者：
Chiou, Tzyy-Jen
中科院分区：
文献类型：
--
作者：
Aung, Kyaw;Lin, Shu-I;Chiou, Tzyy-Jen
我们最近证明microRNA399（miR399）通过调节编码拟南芥（Arabidopsis thaliana）中泛素缀合E2酶的UBC 24的表达来控制无机磷酸盐（Pi）稳态。过表达miR399的转基因植物在芽中积累过量的Pi并显示Pi中毒症状。在这项研究中，我们发现，以前确定的Pi过积累，pho2，是由一个单核苷酸突变导致UBC24基因内的早期终止。在pho2突变体中，全长UBC24 mRNA的水平降低，未检测到UBC24蛋白，而Pi缺乏对miR399的上调没有影响。在pho2突变体中，Pi毒性的几个特征与miR399过表达和UBC24 T-DNA敲除植物中的那些相似：Pi吸收和Pi从根到芽的转运增加，并且Pi在叶内的再动员受损。pho2突变的这些表型可以通过引入UBC24的野生型拷贝来拯救。动力学分析表明，在pho2和miR399过表达植物中更大的Pi吸收是由于增加的V-max。大多数PHT1 Pi转运蛋白基因的转录水平没有显着改变，除了PHT1; 8，其表达增强Pi充足的根pho2和miR399-过表达相比，野生型植物。此外，几个细胞器特异性的Pi转运蛋白的表达的变化被注意到，这可能与过量的Pi下细胞内的Pi的再分配。此外，miR399和UBC 24共定位于血管柱中。这一观察结果不仅为miR399和UBC24 mRNA之间的相互作用提供了重要的见解，而且支持它们在Pi易位和再动员中的系统功能。
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 V-max. 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.