基于基因表达谱分析光质调控番茄红素合成的机理

Tomato as one of the main crops cultivated in protected conditions in northern China. The changes for light environment have great impact on fruit quality of tomato, especially the lycopene content under protected conditions. Previous studies have proved that lycopene synthesis regulated by light quality, but the mechanism of molecular is short of detailed exploration. In the present study, tomato varieties with significant different levels of lycopene content are used as material. The tomato plants are irradiated under light emitting diodes (LED) with different light quality throughout the growth period, and then, RNA-Seq method applied to get the gene expression profiles of tomato fruit, and based on the profiles, the candidate genes responded to light quality and regulating key genes expression of lycopene synthesis are preliminarily selected. Then Real-time quantitative PCR is used to make further analysis for expression level of candidate genes. At last, the key genes responded to light quality and playing important role in regulating lycopene synthesis in tomato are determined. It is expected to make clear the gene regulation pathway of light quality affecting lycopene synthesis in tomato in this study, and it is important for well understanding the accumulation of lycopene. Moreover, a great number of candidate genes responded to light quality can be obtained, which provides a basis for the future further study on transgenic test conducted to make sure that some key candidate genes really take part in the synthesis of lycopene.

番茄是我国北方地区的设施主栽作物之一，设施内光环境的变化对番茄红素含量有很大影响。已有研究证明光质可以调节番茄红素的合成，但对其调控机理缺乏深入了解。本项目拟以番茄红素含量差异较大的番茄品种为试材，采用人工光源LED不同光质全生育期照射番茄植株，通过RNA-Seq技术获得番茄果实的基因表达谱，初步筛选出番茄中对光质响应且调控番茄红素合成关键基因表达的候选基因，然后采用实时定量RT-PCR对候选基因的表达量做进一步分析，找出对光质响应且在调控番茄红素合成中发挥功能的关键基因。进一步探明光质影响番茄红素合成的基因调控途径，对理解番茄红素的积累有重要意义。同时，可以获得一批对光质响应的候选基因，为通过转基因试验对筛选的关键基因在调控番茄红素合成方面进行功能验证的后续研究奠定基础。

筛选出了适宜番茄植株生长，提高叶绿素含量和光合性能，促进干物质积累和壮苗指数增加的红蓝组合光比例3R1B。在前期筛选的适宜红蓝组合光比例的基础上，进一步证明，该比例的红蓝组合光有利于碳水化合物的积累，且通过提高番茄红素生物合成关键酶基因GGPS和PSY1的转录水平和活性，促进番茄红素合成。此外，3R1B处理能够显著促进番茄红素的直接合成前体牻牛儿牻牛儿基焦磷酸的积累，进而加速15-顺式-八氢番茄红素、六氢番茄红素、前番茄红素和全反式番茄红素的转化，最终促进番茄红素的合成。这可能与该光质诱导牻牛儿基牻牛儿基焦磷酸合成酶基因GGPS及八氢番茄红素合成酶家族基因PSY1有关。通过转录组分析初步筛选出参与番茄红素合成且明显受光质调控的酶基因GGPS、PSY1、PDS、ZDS、CRTISO、LCYb、LCYe、CHYB和ZEP。其中，红蓝光质正向调控GGPS、PSY1、PDS、ZDS、CRTISO、CHYB和ZEP的表达量，LCYb和LCYe 则表达受到抑制，从而使番茄红素大量积累，说明干扰下游基因的表达可以提高番茄红素的含量。