Tao Xiang, Fang Yang, Huang Meng-Jun, Xiao Yao, Liu Yang, Ma Xin-Rong, Zhao Hai
Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, Sichuan, 610041, China.
Key Laboratory of Environmental and Applied Microbiology, Chinese Academy of Sciences, Chengdu, 610041, China.
BMC Genomics. 2017 Feb 15;18(1):166. doi: 10.1186/s12864-017-3559-z.
As the fastest growing plant, duckweed can thrive on anthropogenic wastewater. The purple-backed duckweed, Landoltia punctata, is rich in starch and flavonoids. However, the molecular biological basis of high flavonoid and low lignin content remains largely unknown, as does the best method to combine nutrients removed from sewage and the utilization value improvement of duckweed biomass.
A combined omics study was performed to investigate the biosynthesis of flavonoid and the metabolic flux changes in L. punctata grown in different culture medium. Phenylalanine metabolism related transcripts were identified and carefully analyzed. Expression quantification results showed that most of the flavonoid biosynthetic transcripts were relatively highly expressed, while most lignin-related transcripts were poorly expressed or failed to be detected by iTRAQ based proteomic analyses. This explains why duckweed has a much lower lignin percentage and higher flavonoid content than most other plants. Growing in distilled water, expression of most flavonoid-related transcripts were increased, while most were decreased in uniconazole treated L. punctata (1/6 × Hoagland + 800 mg•L uniconazole). When L. punctata was cultivated in full nutrient medium (1/6 × Hoagland), more than half of these transcripts were increased, however others were suppressed. Metabolome results showed that a total of 20 flavonoid compounds were separated by HPLC in L. punctata grown in uniconazole and full nutrient medium. The quantities of all 20 compounds were decreased by uniconazole, while 11 were increased and 6 decreased when grown in full nutrient medium. Nutrient starvation resulted in an obvious purple accumulation on the underside of each frond.
The high flavonoid and low lignin content of L. punctata appears to be predominantly caused by the flavonoid-directed metabolic flux. Nutrient starvation is the best option to obtain high starch and flavonoid accumulation simultaneously in a short time for biofuels fermentation and natural products isolation.
浮萍作为生长最快的植物，能够在人为废水中茁壮生长。紫背浮萍（Landoltia punctata）富含淀粉和类黄酮。然而，其高类黄酮和低木质素含量的分子生物学基础在很大程度上仍不为人知，同时，将污水中去除的养分与提高浮萍生物质利用价值相结合的最佳方法也尚不清楚。
进行了一项联合组学研究，以调查紫背浮萍在不同培养基中生长时类黄酮的生物合成及代谢通量变化。鉴定并仔细分析了与苯丙氨酸代谢相关的转录本。表达定量结果表明，大多数类黄酮生物合成转录本相对高表达，而大多数与木质素相关的转录本表达较差或通过基于iTRAQ的蛋白质组分析未能检测到。这解释了为什么浮萍的木质素百分比比大多数其他植物低得多，而类黄酮含量却更高。在蒸馏水中生长时，大多数与类黄酮相关的转录本表达增加，而在烯效唑处理的紫背浮萍（1/6×霍格兰德培养基+800mg•L烯效唑）中大多数转录本表达下降。当紫背浮萍在完全营养培养基（1/6×霍格兰德培养基）中培养时，超过一半的这些转录本表达增加，然而其他转录本则受到抑制。代谢组学结果表明，通过HPLC在烯效唑和完全营养培养基中生长的紫背浮萍中总共分离出20种类黄酮化合物。烯效唑使所有20种化合物的含量降低，而在完全营养培养基中生长时，11种增加，6种减少。营养饥饿导致每个叶状体下侧明显积累紫色。
紫背浮萍的高类黄酮和低木质素含量似乎主要是由类黄酮导向的代谢通量引起的。营养饥饿是在短时间内同时获得高淀粉和类黄酮积累以用于生物燃料发酵和天然产物分离的最佳选择。
