BACKGROUND Gossypol is a specific secondary metabolite in Gossypium species. It not only plays a critical role in development and self-protection of cotton plants, but also can be used as important anti-cancer and male contraceptive compound. However, due to the toxicity of gossypol for human beings and monogastric animals, the consumption of cottonseeds was limited. To date, little is known about the gossypol metabolism in cotton plants. RESULTS In this study, we found that cotyledon was the primary source of gossypol at the seed germination stage. But thereafter, it was mainly originated from developing roots. Grafting between glanded and glandless cotton as well as sunflower rootstocks and cotton scion revealed that gossypol was mainly synthesized in the root systems of cotton plants. And both glanded and glandless cotton roots had the ability of gossypol biosynthesis. But the pigment glands, the main storage of gossypol, had indirect effects on gossypol biosynthesis. In vitro culture of root and rootless seedling confirmed the strong gossypol biosynthesis ability in root system and the relatively weak gossypol biosynthesis ability in other organs of the seedling. Expression profiling of the key genes involved in the gossypol biosynthetic pathway also supported the root as the major organ of gossypol biosynthesis. CONCLUSIONS Our study provide evidence that the cotton root system is the major source of gossypol in both glanded and glandless cottons, while other organs have a relatively weak ability to synthesize gossypol. Gossypol biosynthesis is not directed related to the expression of pigment glands, but the presence of pigment glands is essential for gossypol accumulation. These findings can not only clarify the complex regulation network of gossypol metabolism, but it could also accelerate the crop breeding process with enhanced commercial values.

中文翻译：

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棉根是棉酚生物合成和积累的主要来源。

背景技术棉酚是棉属物种中的特定次级代谢产物。它不仅在棉花植株的发育和自我保护中起着至关重要的作用，而且还可以用作重要的抗癌和雄性避孕药。但是，由于棉酚对人类和单胃动物具有毒性，因此棉籽的消费受到限制。迄今为止，对棉植物中棉酚代谢的了解还很少。结果在这项研究中，我们发现子叶是种子萌发阶段棉酚的主要来源。但此后，它主要起源于发展中的根源。在无花果和无花果棉花以及向日葵砧木和棉接穗之间进行嫁接表明，棉酚主要在棉花植物的根系中合成。腺体和非腺体的棉根都具有棉酚的生物合成能力。但是，作为棉酚的主要贮藏物的色素腺对棉酚的生物合成具有间接影响。根和无根幼苗的体外培养证实了根系中的棉酚生物合成能力强，而幼苗其他器官中的棉酚生物合成能力相对弱。棉酚生物合成途径中涉及的关键基因的表达谱也支持了根作为棉酚生物合成的主要器官。结论我们的研究提供了证据，证明棉花的根系是无棉腺和无腺棉中棉酚的主要来源，而其他器官合成棉酚的能力相对较弱。棉酚的生物合成与色素腺的表达无关，但是色素腺的存在对于棉酚的积累至关重要。这些发现不仅可以阐明棉酚代谢的复杂调控网络，而且还可以通过提高商业价值来加速作物育种过程。