Phytochromes are red and far-red light receptors in plants that control growth and development in response to changes in the environment. Light-activated phytochromes enter the nucleus and act on a set of downstream signalling components to regulate gene expression. PHYTOCHROME INTERACTING FACTORs (PIFs) belong to the basic helix-loop-helix family of transcription factors and directly bind to light-activated phytochromes. Potential homologs of PIFs have been identified in ferns, bryophytes, and streptophyte algae, and it has been shown that the potential PIF homologs from Physcomitrella patens, PIF1 to PIF4, have PIF function when expressed in Arabidopsis. However, their function in Physcomitrella is still unknown. Seed plant PIFs bind to G-box containing promoters and therefore we searched the Physcomitrella genome for genes that contain G-boxes in their promoter. Here, we show that Physcomitrella PIFs activate these promoters in a G-box dependent manner, suggesting that they could be direct PIF targets. Furthermore, we generated Physcomitrella pif1, pif2, pif3 and pif4 knock out mutant lines and quantified expression of potential PIF direct target genes. Expression of these genes was generally reduced in pif mutants compared to the wildtype but for several genes the relative induction upon a short light treatment was higher in pif mutants than the wildtype. In contrast, expression of these genes was strongly repressed in continuous light, and pif mutants showed partial downregulation of these genes in the dark. Thus, the overall function of PIFs in light-regulated gene expression might be an ancient property of PIFs. This article is protected by copyright. All rights reserved.

中文翻译：

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苔藓 Physcomitrella patens 中的光敏色素相互作用因子调节光控基因表达

光敏色素是植物中的红光和远红光受体，可根据环境变化控制生长和发育。光激活光敏色素进入细胞核并作用于一组下游信号成分以调节基因表达。光敏色素相互作用因子 (PIF) 属于转录因子的基本螺旋-环-螺旋家族，直接与光激活光敏色素结合。已经在蕨类植物、苔藓植物和链藻藻类中鉴定了 PIF 的潜在同源物，并且已经表明，来自 Physcomitrella patens 的潜在 PIF 同源物 PIF1 到 PIF4 在拟南芥中表达时具有 PIF 功能。然而，它们在 Physcomitrella 中的功能仍然未知。种子植物 PIF 与包含 G-box 的启动子结合，因此我们在 Physcomitrella 基因组中搜索了在其启动子中包含 G-box 的基因。在这里，我们展示了 Physcomitrella PIFs 以依赖 G-box 的方式激活这些启动子，表明它们可能是直接的 PIF 目标。此外，我们生成了 Physcomitrella pif1、pif2、pif3 和 pif4 敲除突变系并量化了潜在 PIF 直接靶基因的表达。与野生型相比，这些基因在 pif 突变体中的表达通常降低，但对于一些基因，短光处理后的相对诱导在 pif 突变体中高于野生型。相比之下，这些基因的表达在连续光照下受到强烈抑制，而 pif 突变体在黑暗中显示出这些基因的部分下调。因此，PIFs 在光调节基因表达中的整体功能可能是 PIFs 的一个古老特性。本文受版权保护。版权所有。