The A and B forms of plastid DNA-dependent RNA polymerase from mustard (Sinapis alba L.) transcribe the same genes in a different developmental context
The A and B forms of plastid DNA-dependent RNA polymerase from mustard (Sinapis alba L.) transcribe the same genes in a different developmental context
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DOI：
10.1007/s004380050621
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发表时间：
1997-12
期刊：
影响因子：
--
通讯作者：
T. Pfannschmidt;G. Link
中科院分区：
文献类型：
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作者：
T. Pfannschmidt;G. Link
芥子体中存在两种RNA聚合酶，分别称为A(cp-polA)和B(cp-polB)。在体外，这两种酶对DNA结合的要求不同，但都与同一组叶绿体启动子结合，并从同一组叶绿体启动子转录。B酶对利福平(Rif )敏感，而A酶不敏感。当幼苗在Rif存在下生长时，与光合作用相关的叶绿体基因rbcLandpsbA的RNA池大小比未处理的对照组小，而非光合作用基因rps16、trnG、rrnandrpoB的转录本几乎不受药物的影响。RbcLandpsbA转录本的Rif抑制模式反映了A和B酶在不同阶段和光/暗条件下的相对丰度。因此，这些基因可以在体内被这两种酶中的任何一种转录，而非光合作用基因主要或仅由A酶或另一种Rif抗性的质体聚合酶转录。在对Rif抑制进行测试的几个核基因转录本中，只有Rubisco的叶绿体结合小亚基的RbcS基因家族的转录本显示池大小减小，这可能意味着存在协调不同细胞间基因表达模式的机制。
Two RNA polymerases, termed A (cp-pol A) and B (cp-pol B), are known to be present in mustard plastids. In vitro, the two enzymes have different requirements for DNA binding, but both bind to, and transcribe from, the same set of chloroplast promoters. The B enzyme is sensitive to rifampicin (Rif ), whereas the A enzyme is not. When seedlings were grown in the presence of Rif, RNA pool sizes of the photosynthesis-related plastid genesrbcLandpsbAwere smaller than in untreated controls, whereas transcripts of the non-photosynthetic genesrps16,trnG,rrnandrpoBremained virtually unaffected by the drug. The Rif inhibition patterns ofrbcLandpsbAtranscripts reflect the relative abundance of the A and B enzymes at different stages and light/dark conditions. These genes can thus be transcribed by either of the two enzymes in vivo, whereas the non-photosynthetic genes are transcribed mostly or exclusively by the A enzyme, or by another Rif-resistant plastid polymerase. Among several nuclear gene transcripts that were tested for Rif inhibition, only those of theRbcSgene family for the plastid-bound small subunit of Rubisco revealed a decrease in pool size, which may imply that mechanisms exist that serve to coordinate patterns of gene expression in the different cellular compartments.