Department of Agronomy, Zhejiang University, Hangzhou, 310058, Zhejiang, China.
USDA-ARS, Southern Plains Agricultural Research Center, College Station, TX, 77845, USA.
BMC Plant Biol. 2020 Feb 27;20(1):88. doi: 10.1186/s12870-020-2294-9.
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.
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.
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.
棉酚是棉属植物中特有的一种次生代谢物。它不仅在棉花植物的发育和自我保护中起着关键作用，还可用作重要的抗癌和男性避孕药化合物。然而，由于棉酚对人类和单胃动物的毒性，棉籽的食用受到了限制。迄今为止，人们对棉花植物中棉酚的代谢知之甚少。
在本研究中，我们发现子叶是种子萌发阶段棉酚的主要来源。但此后，它主要来源于发育中的根。棉属有腺体和无腺体棉花以及向日葵砧木和棉花接穗之间的嫁接表明，棉酚主要在棉花植物的根系中合成。有腺体和无腺体的棉花根都具有棉酚生物合成的能力。但是，色素腺体是棉酚的主要储存器官，对棉酚的生物合成只有间接影响。离体培养根和无根幼苗证实了根系具有很强的棉酚生物合成能力，而幼苗的其他器官则具有较弱的棉酚生物合成能力。参与棉酚生物合成途径的关键基因的表达谱也支持根是棉酚生物合成的主要器官。
我们的研究提供了证据表明，有腺体和无腺体棉花的根系统是棉酚的主要来源，而其他器官合成棉酚的能力较弱。棉酚的生物合成与色素腺体的表达无关，但色素腺体的存在是棉酚积累的必要条件。这些发现不仅可以阐明棉酚代谢的复杂调控网络，还可以加速具有增强商业价值的作物育种进程。
