Regulation of chloroplast gene expression by the maturase MatK

内含子成熟酶Matk是叶绿体基因组中唯一可能编码的RNA剪接因子。与相关的单特异性细菌成熟酶不同，Matk能够与多个内含子结合。虽然所有其他叶绿体RNA加工因子都是核编码的，但在所有自养的、含第二内含子的链柄植物的叶绿体基因组中，Matk都存在。由于细菌成熟酶已被证明可以调节自身的表达，这里假设Matk也参与了调控反馈环，该环要求Matk在叶绿体中顺式表达，并阻止基因转移到细胞核。为了验证这一假说，我们提出了一个三管齐下的方法：(1)我们将试图通过跨体方法干扰Matk与其自身RNA的相互作用。(2)为了拥抱更大的Matk网络，我们将测量在烟草发育过程中与Matk相互作用或依赖于Matk功能的各种已知成分的动力学。这将允许开发依赖于Matk的基因表达调控的数学模型，以便识别网络中的关键步骤/因素。(3)为了更好地了解Matk的生化网络，我们将利用质谱学和其他生化技术对含有Matk的核糖核蛋白颗粒进行表征。

The intron maturase MatK is the only putative RNA splicing factor encoded in the chloroplast genome. Different from related monospecific bacterial maturases, MatK is capable of associating with multiple introns. While all other chloroplast RNA processing factors are nuclear encoded, MatK has been maintained in the chloroplast genome in all autotrophic, group II intron-containing streptophytes. Because of the fact that bacterial maturases have been demonstrated to regulate their own expression, it is here hypothesized that MatK is also involved in regulatory feed-back loops that require its expression in cis in the chloroplast and prevent transfer of the gene to the nucleus. To test this hypothesis, a three-pronged approach is proposed: (1) We will try to perturb the interaction of MatK with its own RNA by transplastomic approaches. (2) To embrace the larger MatK-network we will measure kinetics of various components known to interact with MatK or to be dependent on MatK function across tobacco development. This will allow developing a mathematical model of MatK-dependent regulation of gene expression in order to identify critical steps/factors in the network. (3) In order to understand also the biochemical network of MatK, we will characterize MatK-containing ribonucleoprotein particles by mass-spectrometry and additional biochemical techniques.