果胶质是结构和组成最为复杂的细胞壁多糖。拟南芥种皮粘液质是一种富含果胶质的特化细胞壁，已成为研究果胶质多糖合成及其调控机制的理想的模式体系之一。I型鼠李半乳糖醛酸聚糖（RG-I）是拟南芥种皮粘液质的主要成分（约占90%）。近年来利用拟南芥种皮粘液质作为研究体系，已鉴定出多个参与果胶RG-I底物前体转运和主链合成的关键基因，但是有关果胶RG-I生物合成的转录调控机制尚不清楚。申请人前期利用拟南芥种皮粘液质作为研究体系，鉴定出了2个参与种皮粘液质中RG-I合成的MADS-box 转录因子(SHP1和SHP2)，本项目拟深入解析SHP1和SHP2在果胶RG-I生物合成中的功能，通过ChIP-Seq、RNA-seq和酵母双杂交等手段筛选其调控的下游靶标与互作蛋白，阐明SHP1和SHP2参与粘液质果胶RG-I合成的分子机制和调控网络。研究结果将有助于加深对植物果胶质多糖合成与调控机制的认识。

Pectin is structurally and functionally the most complex polysaccharide in plant cell walls. The Arabidopsis thaliana seed coat mucilage is a specialized type of cell wall mainly composed of pectic polysaccharides, and has become one of the ideal model systems for the study of the biosynthesis and regulation mechanisms of pectic polysaccharides. Rhamnogalacturonan I (RG-I) is the major component of the Arabidopsis seed coat mucilage, accounting for more than 90% of the total ploysaccharides. Although several key players involved in the transport of the RG-I precursor and the biosynthesis of RG-I backbone have been identified by utilizing the Arabidopsis seed coat mucilage as the model system in recent years, the molecular mechanisms underlying the transcriptional regulation of RG-I biosynthesis remain largely unknown. In our preliminary study, two MADS-box transcription factors SHP1 and SHP2 were identified to be involved in the biosynthesis of RG-I in Arabidopsis seed coat mucilage. The current project will aim to characterize the functional roles of SHP1 and SHP2 in the RG-I biosynthesis. The downstream target genes and interaction proteins of SHP1 and SHP2 will be identified by ChIP-seq, RNA-seq and Yeast two hybridization techniques. In addition, the molecular mechanisms and the regulation networks governing RG-I biosynthesis in seed coat mucilage will be elucidated. The results obtained will deepen our understanding on the biosynthesis and regulation mechanisms of pectin polysaccharides.