蓖麻种子油脂累积与可溶性糖变化的关系

The Correlation Between Soluble Carbohydrate Metabolism and Lipid Accumulation in Castor Seeds

通过高效液相色谱、RNA-seq测序和放射性碳同位素示踪等技术研究了蓖麻种子发育过程中可溶性糖代谢与油脂累积过程的关系。结果表明,蓖麻种子可溶性糖主要由葡萄糖、果糖和蔗糖构成。随着种子发育和油脂累积,可溶性糖含量呈现明显的下降趋势。其中蔗糖含量变化与油脂累积存在极显著的负相关性(r=0.980)。在种子发育早期,己糖/蔗糖比值较高,糖代谢相关基因大量表达,其中蔗糖合成酶在蔗糖代谢过程中起关键性作用;而在发育中后期,随着种子油脂快速累积,己糖/蔗糖比值和糖代谢水平下降,参与糖代谢的相关基因表达量下调,而脂肪酸合成与油脂累积相关基因表达量明显升高。通过14C蔗糖同位素示踪实验证实:降低种子蔗糖摄入量可以显著抑制糖类向油脂转化,限制蓖麻种子油脂累积。因此,可溶性糖代谢(主要是蔗糖)在蓖麻种子油脂累积过程中具有重要作用。

The relationship between soluble carbohydrates metabolism and lipid accumulation in the development of castor seeds was studied by HPLC,RNA-seq sequencing and radioactive carbon isotope tracing method. Soluble carbohydrates in developing castor seeds were mainly composed of glucose,fructose and sucrose,and decreased obviously with seed development and oil accumulation. The significant negative correlation between sucrose content and lipid accumulation（r=0.980）was observed. Hexose-to-sucrose ratio was much higher and the genes related to carbohydrates metabolism were highly expressed in the early stage of seed development. Especially,sucrose synthase played the key role in carbohydrates metabolism. Hexose-to-sucrose ratio was decreased and the genes involved in carbohydrates metabolism were down regulated with the rapid accumulation of seed oil during the middle and late developmental stages,while the expressions of genes related to fatty acid synthesis and lipid accumulation increased significantly. Confirmed by 14C-sucrose isotope tracing experiments,the conversion of carbohydrates to oil was significantly inhibited by reducing the sucrose intake;consequently lipid accumulation was limited in developing castor seeds. Therefore,soluble carbohydrates metabolism（mainly sucrose）may play an important role in the process of lipid accumulation in castor seeds.