Carotology: Are apocarotenoids conserved modulators of streptophyte physiology?

最早的陆地植物面临的一个主要挑战是克服环境压力。陆生植物的质体被认为是通过发出信号来感知环境信号的中枢，将质体与细胞生理联系在一起。这些信号的一个主要类别是类胡萝卜素裂解产生的类胡萝卜素。在MAdLand的第一个资助期，我和我的团队收集了一些数据，表明陆地植物和链藻共同产生一系列与压力相关的类胡萝卜素，这些类胡萝卜素被称为胚胎中的信号。现在，我们想了解这些分子引发了哪些生理和分子反应。我们将验证类伪胡萝卜素β-环柠檬醛、β-离子酮和二氢锕二内酯诱导与应激信号相关的保守反应模式的假设；在所有工作中，我们将使用MAdLand系统Mesotaenium endlicherium， Zygnema circumcarinatum和Physcomitrium patens作为陆地植物参考。为了分析对类伪麻素的反应，我们将追求三个协同目标：(1)测量类伪麻素对刺槐植物和陆地植物生长、光生理的影响，以及对上游类异戊二烯代谢的反馈；我们将阐明陆地植物和藻类共享的类伪胡萝卜素的生理影响。(2)推断出6亿年链藻进化中由类麻虫引发的全球响应模式；整合RNAseq和磷酸化蛋白质组学数据将确定全面的反应模式-信号转导到下游反应的候选者-我们可以通过比较来推断共享的同源信号网络。(3)探讨信号通路的保守性；虽然类胡萝卜素的一系列作用将在1和2中以自上而下的方法进行评估，但我们也有明确的候选物质：植物激素水杨酸和中胚轴菌、Zygnema和Physcomitrium中的细长下胚轴5 （HY5）和光敏色素相互作用因子3 （PIF3）的（共）同源物。我们将通过(i)与已经产生的patens Physcomitrium hy5和pif敲除突变体中的藻类基因的种间互补实验和（ii）水杨酸定量来测试这些途径的保守性。总之，我们将获得有关类伪胡萝卜素生理影响的综合数据；同时，我们将深入研究信号使用自上而下和有针对性的候选人为基础的方法。我们的数据将被投射到芦苇植物的系统发育上，并与已发表的陆地植物数据和链藻共表达数据进行比较。综合起来，我们将解决MAdLand （i-iv）的四个定义的核心主题：(i)测试通过类胡萝卜素在链藻中进化来调节应激生理的分子基础；（ii）推断这些调节模式发生在陆地植物和刺槐科的最后共同祖先中；（iii）探索它们作为分子适应在应对（iv）非生物陆地挑战中的作用。

One major challenge for the earliest land plants was overcoming environmental stressors. The plastid of land plants is recognized as a hub for sensing environmental cues by emanating signals, linking plastid and cell physiology. A major class of these signals are the apocarotenoids that emerge from cleavage of carotenoids. In the first funding period of MAdLand, my team and I have garnered data that land plants and streptophyte algae share the production of a range of stress-relevant apocarotenoids known as signals in embryophytes. Now, we want to understand which physiological and molecular responses these molecules elicit. We will test the hypothesis that the apocarotenoids β-cyclocitral, β-ionone, and dihydroactinidiolide induce conserved response patterns tied with stress signaling; for all work, we will use the MAdLand systems Mesotaenium endlicherianum, Zygnema circumcarinatum, and Physcomitrium patens as a land plant reference. To dissect responses to apocarotenoids, we will pursue three synergistic objectives: (1) Measure the impact of apocarotenoids on zygnematophyte and land plant growth, photophysiology, and feedbacks on upstream isoprenoid metabolism; we will illuminate the physiological impact of apocarotenoids shared by land plants and algae. (2) Infer apocarotenoid-triggered global response patterns shared across 600 million years of streptophyte evolution; integrating RNAseq and phosphoproteomic data will pinpoint comprehensive response patterns—candidates for signal transduction to downstream responses—that we can compare to infer a shared homologous signaling network. (3) Probe the conservation of the signaling pathway; while a range of effects of apocarotenoids will be assessed in 1 and 2 in a top-down approach, we also have clear candidates: the phytohormone salicylic acid and (co-)orthologs of ELONGATED HYPOCOTYL 5 (HY5) and PHYTOCHROME INTERACTING FACTOR 3 (PIF3) in Mesotaenium, Zygnema, and Physcomitrium. We will test for the conservation of these routes via (i) inter-species complementation experiments with the algal genes in Physcomitrium patens hy5 and pif knock-out mutants that were already generated and (ii) salicylic acid quantification. In sum, we will obtain comprehensive data on the physiological impact of apocarotenoids; concomitantly, we will delve into signaling using a top-down and a targeted candidate-based approach. Our data will be projected onto the phylogeny of Phragmoplastophyta and compared to published data on land plants and co-expression data on streptophyte algae. Combined, we will address four defined core topics of MAdLand (i-iv): (i) testing that a molecular chassis for modulation of stress physiology through apocarotenoids evolved in streptophyte algae; (ii) inferring that these regulatory patterns occurred in the last common ancestor of land plants and Zygnematophyceae; (iii) probing their role as molecular adaptations in the response to (iv) abiotic terrestrial challenges.