Tetrahydrofolate Modulates Floral Transition through Epigenetic Silencing

Abstract

Folates, termed from tetrahydrofolate (THF) and its derivatives, function as coenzymes in one-carbon transfer reactions and play a central role in synthesis of nucleotides and amino acids. Dysfunction of cellular folate metabolism leads to serious defects in plant development; however, the molecular mechanisms of folate-mediated cellular modifications and physiological responses in plants are still largely unclear. Here, we reported that THF controls flowering time by adjusting DNA methylation-regulated gene expression in Arabidopsis (). Wild-type seedlings supplied with THF as well as the high endogenous THF content mutant exhibited significant up-regulation of the flowering repressor of and thereby delaying floral transition in a dose-dependent manner. Genome-wide transcripts and DNA methylation profiling revealed that THF reduces DNA methylation so as to manipulate gene expression activity. Moreover, in accompaniment with elevated cellular ratios between monoglutamylated and polyglutamylated folates under increased THF levels, the content of -adenosylhomo-Cys, a competitive inhibitor of methyltransferases, was obviously higher, indicating that enhanced THF accumulation may disturb cellular homeostasis of the concerted reactions between folate polyglutamylation and folate-dependent DNA methylation. In addition, we found that the loss-of-function mutant of CG DNA methyltransferase MET1 displayed much less responsiveness to THF-associated flowering time alteration. Taken together, our studies revealed a novel regulatory role of THF on epigenetic silencing, which will shed lights on the understanding of interrelations in folate homeostasis, epigenetic variation, and flowering control in plants.

Epigenomic Regulatory Mechanism of Flowering in Apple Demonstrated in Two Varieties with Contrasted Flowering Behaviors

“…Numerous studies have reported the regulation mechanism of owering process in their whole life cycle of plants, including oral induction [37], juvenile-to-adult transition [38], reproduction [12], and oral organ identity process [39] involved in transcriptional and post-transcriptional, and epigenetic regulation in multiple owering pathways. DNA methylation as epigenetic modi cations regulation is critical for oral induction and formation in woody plants, such as Apple [3], Pear [16], and Citrus [18].…”

“…3). Indeed, the DMRs happened on various genomic regions (i.e., promoter, gene-body, or intron) may lead to different gene transcript levels in multiple plants [3,37], indicating that gene transcription is closely related to methylation. In our data, we found that methylation levels had a negative regulatory relationship with gene expression levels involved in the CG, CHG, and CHH contexts in the gene-body region (Fig.…”

Seeing the unseen: a trifoliate (MYB117) mutant allele fortifies folate and carotenoids in tomato fruits

“…Considering that in Arabidopsis, high folate levels delay inflorescence initiation (Wang et al, 2017), we examined whether the trifoliate mutation influenced folate levels. (e) Fruit phenotype at the mature-green (MG), breaker (BR), and red-ripe (RR) stages of ripening.…”

Integrated analysis between folate metabolites profiles and transcriptome of panicle in foxtail millet

“…3.1 谷穗发育过程中叶酸合成途径关键基因表 达影响叶酸代谢物组成特征 谷子籽粒富含叶酸, 可作为人们日常摄入天然 叶酸的来源之一。深入探讨其籽粒中叶酸代谢谱分 布特征及相关基因表达模式, 为挖掘叶酸代谢关键 基因, 获得高稳定性叶酸材料, 培育高品质谷子品 种提供思路。Lian 等 [19] 在研究玉米籽粒发育过程叶 酸含量发现, 随着生育期的推进, 叶酸含量呈下降 趋势, 这与本研究中谷穗叶酸含量变化规律一致。 成熟小穗鲜样中所测得的叶酸总含量为 1.89 μg g 1 FW, 与本实验室测定干样含量存在差异(2.02 μg g 1 DW) [12] , 这是含水量差异所致。此外, 本研究仅用 含量降低的重要原因。Lian 等 [19] 对玉米籽粒中叶酸 含量的研究发现, 在未成熟籽粒中的 5-M-THF 的含 量高于成熟玉米籽, 进一步推测 5-M-THF 在穗发育 前期高含量可能是由于籽粒发育早期一碳循环更活 跃造成; Blancquaert 等 [21] 在水稻 pABA 含量上也观 察到类似的情况。除此之外, 叶酸介导所有生物必 需的一碳转移反应, 如 10-F-THF 和 5,10-CH=THF 衍生物的代谢参与嘌呤和胸苷酸的产生 [22] , SHMT1 通过参与羟甲基转移为生物合成提供一碳单位, 并 影响叶酸代谢; DHFR2 作为一碳途径和叶酸合成途 径的关键基因, 与叶酸主要化合物之间联系紧密。 在 拟南芥中, THF 合成的倒数第 2 个步骤是由双功能二 氢叶酸还原-胸苷酸合成酶(DHFR-TS)催完成 [23][24] 。在 这类双功能酶中, DHFR 酶位于 N 端, 将经过 TS 形 成的 DHF 还原为 THF [25] 。此外, 在本研究中发现, 物的生长发育过程中发挥重要的调控作用 [27] 。本研 究发现, 16 个叶酸合成关键基因发生了不同类型的可 变剪切, 且在穗发育不同时期可变剪切数目不同。 研究表明, IR 的发生可在转录本中插入提前终止密 码子, 使基因表达下调 [28] [33] 。叶酸在甲基化反应中提供 S-腺 苷蛋氨酸, 是甲基化反应的关键因素 [34] 。本研究发 现, 一碳代谢甲基化关键酶基因 DDM1、DDM2、 MET1、MET3 与叶酸合成基因 DHFR1、DHFR2 之 间有直接关系, 但叶酸代谢基因与甲基化相关基因 之间具体调控关系尚不明确。Wang 等 [35]…”