转录因子BjNFL调控茎瘤芥发育的分子机制研究

Tuber mustard (Brassica juncea var. tumida Tsen et Lee) is a famous vegetable for its swollen stem which can serve as the raw material for Fuling mustard. One of the most important factors affecting the yield of this vegetable is length of vegetative growth. Therefore, uncovering the developmental mechanism of tuber mustard especially the maturation period is critical for improving quality and yield of tuber mustard. In previous study, we found the expression of a bHLH transcription factor, NO FLOWERING IN SHORT DAY (BjNFL), was significantly up regulated during stem development base on the transcriptomic data. In Arabidopsis, NFL promote flowering under non-inductive short day conditions through the gibberellins (GA) signaling pathway. In addition, it has been reported that stem swelling of tuber mustard is a physiological process affecting by GA and the photoperiod. Base on these data, we propose that BjNFL might play an important role in tuber mustard development at transcriptional regulation level. In the present subject, the expression pattern of BjNFL will be analyzed by Q-PCR. The function of BjNFL will be illustrated by analysing over-expression and RNA interference transgenic plants. Moreover, ChIP-Seq and transcriptomic data will be combined to analysis the target genes of BjNFL from whole genome level. These results will be very helpful to reveal the molecular mechanism of BjNFL in regulating the development of tuber mustard. Hopefully, this study will not only enrich transcription regulation theory of modified stem development, but also provide theoretical basis for variety improving and industrial development of tuber mustard.

茎瘤芥（榨菜）以瘤状茎为收获器官，营养生长期长短是影响茎瘤芥产量的关键因素，研究茎瘤芥发育的调控机制特别是熟性早晚的调控机制对提高茎瘤芥产量和品质有重要意义。研究组前期从茎瘤芥瘤状茎发育的表达谱中筛选出1个bHLH转录因子BjNFL，其表达随着瘤状茎发育持续升高，结合前人在同科模式植物拟南芥中NFL可通过GA调控短日照下开花和茎瘤芥瘤状茎发育与GA密切相关且受光周期调控的结果，本项目提出BjNFL与茎瘤芥发育密切相关的科研假设。拟利用荧光定量PCR研究该基因的表达特性及其对开花调控措施的响应，利用超表达和RNA干扰探明BjNFL在茎瘤芥发育过程中的功能，利用染色质免疫共沉淀结合高通量测序（ChIP-Seq）等技术，筛选其下游调控的靶基因，阐明其参与调控茎瘤芥发育的分子机制。本项目的实施不仅可以丰富变态茎发育的转录调控理论，而且对茎瘤芥产业发展和新品种的选育提供重要理论依据。

茎瘤芥的瘤状茎是涪陵榨菜的原料，瘤状茎的膨大是影响茎瘤芥产量的重要因素，然而目前对茎瘤芥的瘤状茎的膨大机理尚不清楚。本项目利用‘永安小叶’茎瘤芥为材料分析了bHLH转录因子BjuNFL的表达特点，并通过拟南芥转化初步分析了其功能，同时采用了DAP-seq技术结合转录组数据对BjuNFL的下游靶基因进行了筛选，并对关键靶基因的表达和功能进行了分析。取得主要结果如下：BjuNFL在茎瘤芥的瘤状茎快速膨大期的外周组织表达量最高，转基因拟南芥的开花受到抑制，推测其也参与了营养生长向生殖生长转化调控；利用DAP-seq鉴定了44个候选靶基因，分析发现，BjuNFL可能通过调控细胞壁代谢相关基因和细胞大小控制基因来调控茎瘤芥的瘤状茎的膨大过程。本项目初步解析了茎瘤芥BjuNFL转录因子参与调控瘤状茎膨大的调控机制，为深入研究茎瘤芥的瘤状茎的膨大机制提供了重要的理论基础。