Qu Yujiao, Legen Julia, Arndt Jürgen, Henkel Stephanie, Hoppe Galina, Thieme Christopher, Ranzini Giovanna, Muino Jose M, Weihe Andreas, Ohler Uwe, Weber Gert, Ostersetzer Oren, Schmitz-Linneweber Christian
Institut für Biologie, Humboldt-Universität zu Berlin, Berlin, Germany.
Computational Regulatory Genomics, Berlin Institute for Medical Systems Biology, Max Delbrück Center for Molecular Medicine, Berlin, Germany.
Front Plant Sci. 2018 Oct 4;9:1453. doi: 10.3389/fpls.2018.01453. eCollection 2018.
Chloroplasts (and other plastids) harbor their own genetic material, with a bacterial-like gene-expression systems. Chloroplast RNA metabolism is complex and is predominantly mediated by nuclear-encoded RNA-binding proteins. In addition to these nuclear factors, the chloroplast-encoded intron maturase MatK has been suggested to perform as a splicing factor for a subset of chloroplast introns. MatK is essential for plant cell survival in tobacco, and thus null mutants have not yet been isolated. We therefore attempted to over-express MatK from a neutral site in the chloroplast, placing it under the control of a theophylline-inducible riboswitch. This ectopic insertion of MatK lead to a variegated cotyledons phenotype. The addition of the inducer theophylline exacerbated the phenotype in a concentration-dependent manner. The extent of variegation was further modulated by light, sucrose and spectinomycin, suggesting that the function of MatK is intertwined with photosynthesis and plastid translation. Inhibiting translation in the transplastomic lines has a profound effect on the accumulation of several chloroplast mRNAs, including the accumulation of an RNA antisense to , a gene coding for an essential chloroplast ribosomal protein. Our study further supports the idea that MatK expression needs to be tightly regulated to prevent detrimental effects and establishes another link between leaf variegation and chloroplast translation.
叶绿体（以及其他质体）含有自身的遗传物质，并具有类似细菌的基因表达系统。叶绿体RNA代谢十分复杂，主要由核编码的RNA结合蛋白介导。除了这些核因子外，叶绿体编码的内含子成熟酶MatK被认为是叶绿体部分内含子的剪接因子。MatK对烟草中的植物细胞存活至关重要，因此尚未分离到其缺失突变体。因此，我们试图从叶绿体中的一个中性位点过表达MatK，并将其置于茶碱诱导型核糖开关的控制之下。MatK的这种异位插入导致子叶出现斑驳表型。添加诱导剂茶碱会以浓度依赖的方式加剧这种表型。斑驳程度还受到光、蔗糖和壮观霉素的进一步调节，这表明MatK的功能与光合作用和质体翻译相互交织。抑制转基因系中的翻译对几种叶绿体mRNA的积累有深远影响，包括与一个编码叶绿体必需核糖体蛋白的基因的反义RNA的积累。我们的研究进一步支持了MatK表达需要严格调控以防止产生有害影响的观点，并建立了叶斑驳与叶绿体翻译之间的另一个联系。
