R2R3-type MYB transcription factor, CmMYB1, is a central nitrogen assimilation regulator in Cyanidioschyzon merolae
R2R3-type MYB transcription factor, CmMYB1, is a central nitrogen assimilation regulator in Cyanidioschyzon merolae
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DOI：
10.1073/pnas.0902790106
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发表时间：
2009-07-28
影响因子：
11.1
通讯作者：
Tanaka, Kan
中科院分区：
文献类型：
--
作者：
Imamura, Sousuke;Kanesaki, Yu;Tanaka, Kan
植物细胞感知环境氮水平并相应地改变其基因表达以生存;然而，潜在的调控机制仍有待阐明。在这里，我们确定并表征了一个转录因子，负责氮同化基因的表达在一个单细胞的红Cyanidioschyzon merolae。DNA微阵列和北方印迹分析表明，CmMYB 1基因的转录，R2 R3型MYB转录因子，增加氮耗尽后1小时。CmMYB 1蛋白在氮耗竭后2 h开始积累，4 h后达到峰值，与关键氮同化基因CmNRT、CmNAR、CmNIR、CmAMT和CmGS的表达相关。虽然这些氮同化基因的成绩单中检测到硝酸盐生长的细胞，他们消失后，添加优选的氮源，如铵或谷氨酰胺，这表明氮代谢产物阻遏（NCR）机制的存在。氮耗尽诱导的基因表达消失在CmMYB 1无效突变体，和突变体显示出降低细胞活力暴露后的氮耗尽的条件下相比，亲本菌株。染色质免疫沉淀分析表明，CmMYB 1只在氮耗尽条件下特异性地占据这些氮响应启动子区域，并且使用粗细胞提取物的电泳迁移率变动分析揭示了CmMYB 1或含有CmMYB 1的复合物与这些启动子的特异性结合。因此，CmMYB 1是C. merolae。
Plant cells sense environmental nitrogen levels and alter their gene expression accordingly to survive; however, the underlying regulatory mechanisms still remains to be elucidated. Here, we identified and characterized a transcription factor that is responsible for expression of nitrogen assimilation genes in a unicellular red alga Cyanidioschyzon merolae. DNA microarray and Northern blot analyses revealed that transcript of the gene encoding CmMYB1, an R2R3-type MYB transcription factor, increased 1 h after nitrogen depletion. The CmMYB1 protein started to accumulate after 2 h and reached a peak after 4 h after nitrogen depletion, correlating with the expression of key nitrogen assimilation genes, such as CmNRT, CmNAR, CmNIR, CmAMT, and CmGS. Although the transcripts of these nitrogen assimilation genes were detected in nitrate-grown cells, they disappeared upon the addition of preferred nitrogen source such as ammonium or glutamine, suggesting the presence of a nitrogen catabolite repression (NCR) mechanism. The nitrogen depletion-induced gene expression disappeared in a CmMYB1-null mutant, and the mutant showed decreased cell viability after exposure to the nitrogen-depleted conditions compared with the parental strain. Chromatin immunoprecipitation analysis demonstrated that CmMYB1 specifically occupied these nitrogen-responsive promoter regions only under nitrogen-depleted conditions, and electrophoretic mobility shift assays using crude cell extract revealed specific binding of CmMYB1, or a complex containing CmMYB1, to these promoters. Thus, the presented results indicated that CmMYB1 is a central nitrogen regulator in C. merolae.