Goethe University Frankfurt, Max von Laue Str. 9, 60438 Frankfurt, Germany.
Institute of Plant Biochemistry, Cluster of Excellence on Plant Sciences, Heinrich Heine University, 40225 Düsseldorf, Germany.
Plant Cell Physiol. 2017 Nov 1;58(11):1914-1923. doi: 10.1093/pcp/pcx127.
Diatoms, albeit being only distantly related with higher plants, harbor a plant-like cryptochrome (CryP) that was proposed to act as a photoreceptor required for the regulation of some photosynthetic proteins. Plant cryptochromes are involved in the regulation of developmental processes relevant only to multicellular organisms. Their role in the unicellular diatoms to date is mostly enigmatic. To elucidate the function of this plant-like cryptochrome in a unicellular species, we examined the role of CryP in the regulation of transcription in the diatom Phaeodactylum tricornutum by comparative RNA-seq of wild type and CryP knock-down mutants, under prolonged darkness and one hour after onset of blue light. In total, mRNAs of 12,298 genes were identified and more than 70% of the genes could be sorted into functional bins. CryP influenced groups of transcripts in three different ways: some transcripts displayed altered expression under blue light only, others independent of the light condition, and, surprisingly, some were influenced by CryP only in darkness. Genes regulated in any condition were distributed over almost all functional categories. CryP exerted an influence on two other photoreceptors: the genes encoding phytochrome and CPF1, another cryptochrome, which were down-regulated by CryP independent of the light condition. However, the regulatory responses of the affected photoreceptors on transcriptional output were independent. The influence of CryP on the expression of other photoreceptors hints to the existence of a regulatory signaling network in diatoms that includes several cryptochromes and phytochrome, whereby CryP acts as a regulator of transcript abundance under light as well as in darkness.
硅藻与高等植物仅有远缘关系，但却拥有一种类似于植物的隐花色素（CryP），这种隐花色素被认为是调节某些光合作用蛋白所必需的光受体。植物隐花色素参与调节仅与多细胞生物相关的发育过程。迄今为止，它们在单细胞硅藻中的作用在很大程度上仍是个谜。为了阐明这种在单细胞物种中类似于植物的隐花色素的功能，我们通过对野生型和 CryP 敲低突变体在持续黑暗和蓝光照射后 1 小时进行比较 RNA-seq，研究了 CryP 在调控单细胞硅藻三角褐指藻转录中的作用。总共鉴定出了 12298 个 mRNA，其中超过 70%的基因可以归类为功能基因库。CryP 以三种不同的方式影响转录物组：一些转录物仅在蓝光下显示表达改变，另一些则不受光照条件影响，而令人惊讶的是，一些转录物仅在黑暗中受 CryP 影响。在任何条件下受到调控的基因分布在几乎所有的功能类别中。CryP 对另外两种光受体：编码光敏色素和 CPF1 的基因也有影响，这两种光受体的基因在不受光照条件影响的情况下被 CryP 下调。然而，受影响的光受体在转录输出上的调控反应是独立的。CryP 对其他光受体表达的影响暗示在硅藻中存在一个包括几种隐花色素和光敏色素的调节信号网络，其中 CryP 作为光和黑暗条件下转录物丰度的调节剂。
