Department of Botany II, Cologne Biocenter, University of Cologne, Zülpicherstr. 47b, 50674 Cologne, Germany
Department of Botany II, Cologne Biocenter, University of Cologne, Zülpicherstr. 47b, 50674 Cologne, Germany.
Mol Plant. 2014 Jul;7(7):1121-37. doi: 10.1093/mp/ssu064. Epub 2014 May 23.
The concept of retrograde control of nuclear gene expression assumes the generation of signals inside the chloroplasts, which are either released from or sensed inside of the organelle. In both cases, downstream signaling pathways lead eventually to a differential regulation of nuclear gene expression and the production of proteins required in the chloroplast. This concept appears reasonable as the majority of the over 3000 predicted plastidial proteins are encoded by nuclear genes. Hence, the nucleus needs information on the status of the chloroplasts, such as during acclimation responses, which trigger massive changes in the protein composition of the thylakoid membrane and in the stroma. Here, we propose an additional control mechanism of nuclear- and plastome-encoded photosynthesis genes, taking advantage of pathways involved in sugar- or hormonal signaling. Sugars are major end products of photosynthesis and their contents respond very sensitively to changes in light intensities. Based on recent findings, we ask the question as to whether the carbohydrate status outside the chloroplast can be directly sensed within the chloroplast stroma. Sugars might synchronize the responsiveness of both genomes and thereby help to coordinate the expression of plastome- and nuclear-encoded photosynthesis genes in concert with other, more specific retrograde signals.
核基因表达的逆行控制的概念假定在叶绿体内部产生信号，这些信号要么从细胞器内部释放出来，要么在细胞器内部被感知。在这两种情况下，下游信号通路最终导致核基因表达的差异调节和叶绿体中所需蛋白质的产生。这个概念似乎是合理的，因为超过 3000 种预测的质体蛋白大多数是由核基因编码的。因此，细胞核需要了解叶绿体的状态，例如在适应反应期间，这会引发类囊体膜和基质中蛋白质组成的大量变化。在这里，我们提出了一种额外的核基因和质体基因编码光合作用基因的控制机制，利用涉及糖或激素信号的途径。糖是光合作用的主要终产物，其含量对光强度的变化非常敏感。基于最近的发现，我们提出了一个问题，即叶绿体外部的碳水化合物状态是否可以在叶绿体基质内部直接感知。糖可能会使两个基因组的反应同步，从而有助于协调质体基因和核基因编码的光合作用基因与其他更具体的逆行信号一起表达。
