Bahieldin Ahmed, Atef Ahmed, Edris Sherif, Gadalla Nour O, Al-Matary Mohammed, Al-Kordy Magdy A, Ramadan Ahmed M, Bafeel Sameera, Alharbi Mona G, Al-Quwaie Diana A H, Sabir Jamal S M, Al-Zahrani Hassan S, Nasr Mahmoud E, El-Domyati Fotouh M
Department of Biological Sciences, Faculty of Science, King Abdulaziz University (KAU), P.O. Box 80141, 21589 Jeddah, Saudi Arabia.
Department of Biological Sciences, Faculty of Science, King Abdulaziz University (KAU), P.O. Box 80141, 21589 Jeddah, Saudi Arabia.
C R Biol. 2018 Nov-Dec;341(9-10):411-420. doi: 10.1016/j.crvi.2018.10.001. Epub 2018 Oct 26.
Catharanthus roseus is a perennial herb known for the production of important terpenoid indole alkaloids (TIAs) in addition to a variety of phenolic compounds. The goal of the present work was to detect the prolonged effects of MeJA (6 uM) treatment across time (up to 24 days) in order to detect the stepwise response of MeJA-induced genes and pathways in leaves of C. rouses. Prolonged exposure of plants to MeJA (6 uM) treatment for different time points (6, 12 and 24 days) indicated that genes in the indole alkaloid biosynthesis pathway and upstream pathways were triggered earlier (e.g., 6 days) than those in the anthocyanin biosynthesis pathway and its upstream pathways (e.g., 12 days). Three enzymes, e.g., T16H, OMT, and D4H, in the six-step vindoline biosynthesis and two enzymes, e.g., TDC and STR, acting consecutively in the conversion of tryptophan to strictosidine, were activated after 6 days of MeJA treatment. Two other key enzymes, e.g., TRP and CYP72A1, acting concurrently upstream of the TIA biosynthesis pathway were upregulated after 6 days. The genes encoding TDC and STR might concurrently act as a master switch of the TIA pathway towards the production of the indole alkaloids. On the other hand, we speculate that the gene encoding PAL enzyme also acts as the master switch of phenylpropanoid biosynthesis and the downstream flavonoid biosynthesis and anthocyanin biosynthesis pathways towards the production of several phenolic compounds. PAL and the downstream enzymes were activated 12 days after treatment. Cluster analysis confirmed the concordant activities of the flower- and silique-specific bHLH25 transcription factor and the key enzyme in the TIA biosynthesis pathway, e.g., STR. Due to the stepwise response of the two sets of pathways, we speculate that enzymes activated earlier likely make TIA biosynthesis pathway a more favourable target in C. roseus than anthocyanin biosynthesis pathway.
长春花是一种多年生草本植物，除了能产生多种酚类化合物外，还以生产重要的萜类吲哚生物碱（TIAs）而闻名。本研究的目的是检测茉莉酸甲酯（6 μM）处理在不同时间（长达24天）的长期影响，以检测茉莉酸甲酯诱导的基因和途径在长春花叶片中的逐步反应。将植物长时间暴露于茉莉酸甲酯（6 μM）处理不同时间点（6、12和24天）表明，吲哚生物碱生物合成途径及其上游途径中的基因比花青素生物合成途径及其上游途径中的基因更早（如6天）被触发。在茉莉酸甲酯处理6天后，参与长春花碱六步生物合成的三种酶，即T16H、OMT和D4H，以及在色氨酸转化为长春花苷的过程中连续起作用的两种酶，即TDC和STR，被激活。另外两种在TIAs生物合成途径上游同时起作用的关键酶，即TRP和CYP72A1，在6天后上调。编码TDC和STR的基因可能同时作为TIAs途径中吲哚生物碱生产的主开关。另一方面，我们推测编码苯丙氨酸解氨酶（PAL）的基因也作为苯丙烷生物合成以及下游类黄酮生物合成和花青素生物合成途径中几种酚类化合物生产的主开关。处理12天后，PAL和下游酶被激活。聚类分析证实了花和角果特异性bHLH25转录因子与TIAs生物合成途径中的关键酶，如STR的协同活性。由于两组途径的逐步反应，我们推测较早被激活的酶可能使TIAs生物合成途径在长春花中比花青素生物合成途径更易成为有利目标。
