由于全球气候变化,干旱正在成为植物生长和农业生产力的主要威胁。脱落酸(ABA)与植物耐旱性有关,然而,其对植物生长的延缓作用不容忽视。由1-脱氧-D-木酮糖-5-磷酸合酶(DXS)和1-脱氧-D-木酮糖-5-磷酸还原异构酶(DXR)蛋白催化的反应是植物类异戊二烯生物合成中的关键步骤。这里,从决明子基因组中鉴定出5个DXS(CtDXS1-5)和2个DXR(CtDXR1-2)基因。基于包括系统发育在内的多种分析,顺式作用元素,表达模式,和亚细胞定位,CtDXS1和CtDXR1基因可能是控制类异戊二烯生物合成的潜在候选者。有趣的是,CtDXS1转基因植物导致耐旱性,但生长迟缓,而CtDXR1转基因植物表现出增强的耐旱性和增加的生长。通过β-胡萝卜素的比较,叶绿素,野生型和转基因植物中脱落酸(ABA)和赤霉素3(GA3)含量,绝对含量和(或)改变的GA3/ABA水平被认为是耐旱性与植物生长之间平衡的原因。CtDXR1转基因植物的转录组表明,关键基因的转录水平,比如DXS,9-顺式-环氧类胡萝卜素双加氧酶(NCED),ent-kaurene合酶(KS)等,与叶绿素有关,β-胡萝卜素,诱导了ABA和GA3的生物合成,其含量相应增加。总的来说,CtDXR1诱导的权衡效应与植物激素稳态结构的重新设计有关,因此在未来的育种目的中得到了强调。
Due to global climate change, drought is emerging as a major threat to plant growth and agricultural productivity. Abscisic acid (ABA) has been implicated in plant drought tolerance, however, its retarding effects on plant growth cannot be ignored. The reactions catalyzed by 1-deoxy-D-xylulose-5-phosphate synthase (DXS) and 1-deoxy-D-xylulose-5-phosphate reductoisomerase (DXR) proteins are critical steps within the isoprenoid biosynthesis in plants. Here, five DXS (CtDXS1-5) and two DXR (CtDXR1-2) genes were identified from Cassia tora genome. Based on multiple assays including the phylogeny, cis-acting element, expression pattern, and subcellular localization, CtDXS1 and CtDXR1 genes might be potential candidates controlling the isoprenoid biosynthesis. Intriguingly, CtDXS1 transgenic plants resulted in drought tolerance but retardant growth, while CtDXR1 transgenic plants exhibited both enhanced drought tolerance and increased growth. By comparison of β-carotene, chlorophyll, abscisic acid (ABA) and gibberellin 3 (GA3) contents in wild-type and transgenic plants, the absolute contents and (or) altered GA3/ABA levels were suggested to be responsible for the balance between drought tolerance and plant growth. The transcriptome of CtDXR1 transgenic plants suggested that the transcript levels of key genes, such as DXS, 9-cis-epoxycarotenoid dioxygenases (NCED), ent-kaurene synthase (KS) and etc, involved with chlorophyll, β-carotene, ABA and GA3 biosynthesis were induced and their contents increased accordingly. Collectively, the trade-off effect induced by CtDXR1 was associated with redesigning architecture in phytohormone homeostasis and thus was highlighted for future breeding purposes.