Distinct phytochrome actions in nonvascular plants revealed by targeted inactivation of phytobilin biosynthesis
Distinct phytochrome actions in nonvascular plants revealed by targeted inactivation of phytobilin biosynthesis
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DOI：
10.1073/pnas.1201744109
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发表时间：
2012-05-22
影响因子：
11.1
通讯作者：
Tu, Shih-Long
中科院分区：
文献类型：
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作者：
Chen, Yu-Rong;Su, Yi-Shin;Tu, Shih-Long
红光/远红光光感受器光敏色素介导植物的光形态反应。对于光传感和信号传导，光敏色素需要与作为发色团的开链四吡咯分子缔合。四吡咯发色团的生物合成需要铁氧还蛋白依赖性胆色素还原酶（FDBR）的成员。研究表明，LONG HYPOCOTYL 2（HY 2）是开花植物中唯一产生光敏色素光敏色素移动素（P Phi B）的FDBR。然而，在苔藓小立碗藓中，我们发现了第二种FDBR，它催化藻胆素（PUB）的形成，这是一种四吡咯色素，通常在蓝藻和红藻中以蛋白质结合的形式存在。因此，我们将这种酶命名为PUB合酶（PUBS）。当小立碗藓的HY 2和PUBS基因被靶向破坏时，会出现严重的光形态发生表型，包括光敏色素介导的向光性缺陷。这表明HY 2和PUBS在光敏色素介导的非维管植物响应中具有冗余功能。我们的研究还表明，功能PUBS直系同源物中发现的选择石松和绿藻基因组。使用mRNA测序的转录组分析，我们证明了大多数红光响应基因的表达在pubs hy 2双突变体中被错误调节。这些研究表明，苔藓光敏色素快速抑制参与细胞壁组织，转录，激素反应和蛋白质磷酸化的基因的表达，但激活参与光合作用和压力信号在去黄化过程中的基因。我们建议，在非维管植物中，HY 2和PUBS产生结构不同，但功能相似的光敏色素的发色团前体。全光敏色素通过光信号调节生物过程，以有效地重编程基因表达，从而在光下进行营养生长。
The red/far-red light photoreceptor phytochrome mediates photo-morphological responses in plants. For light sensing and signaling, phytochromes need to associate with open-chain tetrapyrrole molecules as the chromophore. Biosynthesis of tetrapyrrole chromophores requires members of ferredoxin-dependent bilin reductases (FDBRs). It was shown that LONG HYPOCOTYL 2 (HY2) is the only FDBR in flowering plants producing the phytochromobilin (P Phi B) for phytochromes. However, in the moss Physcomitrella patens, we found a second FDBR that catalyzes the formation of phycourobilin (PUB), a tetrapyrrole pigment usually found as the protein-bound form in cyanobacteria and red algae. Thus, we named the enzyme PUB synthase (PUBS). Severe photomorphogenic phenotypes, including the defect of phytochrome-mediated phototropism, were observed in Physcomitrella patens when both HY2 and PUBS were disrupted by gene targeting. This indicates HY2 and PUBS function redundantly in phytochrome-mediated responses of nonvascular plants. Our studies also show that functional PUBS orthologs are found in selected lycopod and chlorophyte genomes. Using mRNA sequencing for transcriptome profiling, we demonstrate that expression of the majority of red-light-responsive genes are misregulated in the pubs hy2 double mutant. These studies showed that moss phytochromes rapidly repress expression of genes involved in cell wall organization, transcription, hormone responses, and protein phosphorylation but activate genes involved in photosynthesis and stress signaling during deetiolation. We propose that, in nonvascular plants, HY2 and PUBS produce structurally different but functionally similar chromophore precursors for phytochromes. Holophytochromes regulate biological processes through light signaling to efficiently reprogram gene expression for vegetative growth in the light.