Nambeesan Savithri U, Mattoo Autar K, Handa Avtar K
Department of Horticulture, University of Georgia, Athens, GA, United States.
Sustainable Agricultural Systems Laboratory, USDA-ARS, Beltsville Agricultural Research Center, Beltsville, MD, United States.
Front Plant Sci. 2019 Sep 25;10:1033. doi: 10.3389/fpls.2019.01033. eCollection 2019.
Polyamines (PAs) constituting putrescine (Put), spermidine (Spd), and spermine (Spm) are ubiquitous in all organisms and play essential roles in the growth and developmental processes in living organisms, including plants. Evidences obtained through genetic, biochemical, and transgenic approaches suggest a tight homeostasis for cellular PA levels. Altered cellular PA homeostasis is associated with abnormal phenotypes. However, the mechanisms involved for these abnormalities are not yet fully understood, nor is it known whether cellular ratios of different polyamines play any role(s) in specific plant processes. We expressed a yeast spermidine synthase gene () under a constitutive promoter in tomato and studied the different phenotypes that developed. The constitutive expression of resulted in variable flower phenotypes in independent transgenic lines, some of which lacked fruit and seed set. Quantification of PA levels in the developing flowers showed that the transgenic plants without fruit and seed set had significantly reduced Spd levels as well as low Spd/Put ratio compared to the transgenic lines with normal fruit and seed set. Transcript levels of , , and , which impact gibberellin (GA) metabolism and signaling, were significantly reduced in bud tissue of transgenic lines that lacked fruit and seed set. These findings indicate that PAs, particularly Spd, impact floral organ identity and fruit set in tomato involving GA metabolism and signaling. Furthermore, we suggest that a nexus exists between PA ratios and developmental programs in plants.
多胺（PAs）由腐胺（Put）、亚精胺（Spd）和精胺（Spm）组成，在所有生物体中普遍存在，并在包括植物在内的生物体的生长和发育过程中发挥重要作用。通过遗传、生化和转基因方法获得的证据表明，细胞内多胺水平存在严格的稳态。细胞内多胺稳态的改变与异常表型相关。然而，这些异常所涉及的机制尚未完全了解，不同多胺的细胞比例是否在特定植物过程中发挥作用也不清楚。我们在组成型启动子下在番茄中表达了一个酵母亚精胺合酶基因（），并研究了所产生的不同表型。的组成型表达在独立的转基因系中导致了可变的花表型，其中一些缺乏果实和种子结实。对发育中的花中多胺水平的定量分析表明，与具有正常果实和种子结实的转基因系相比，没有果实和种子结实的转基因植物的Spd水平显著降低，并且Spd/Put比值较低。影响赤霉素（GA）代谢和信号传导的、和的转录水平在缺乏果实和种子结实的转基因系的芽组织中显著降低。这些发现表明，多胺特别是Spd，通过影响GA代谢和信号传导来影响番茄的花器官特性和坐果。此外，我们认为植物中多胺比例与发育程序之间存在联系。
