The Rice BZ1 Locus Is Required for Glycosylation of Arabinogalactan Proteins and Galactolipid and Plays a Role in both Mechanical Strength and Leaf Color
The Rice BZ1 Locus Is Required for Glycosylation of Arabinogalactan Proteins and Galactolipid and Plays a Role in both Mechanical Strength and Leaf Color
复制标题
水稻 BZ1 基因座是阿拉伯半乳聚糖蛋白和半乳糖脂糖基化所必需的，并且在机械强度和叶色中发挥作用
DOI：
10.1186/s12284-020-00400-9
复制
发表时间：
2020-06-17
期刊：
影响因子：
5.5
通讯作者：
Li, Fengcheng
中科院分区：
文献类型：
--
作者：
Liu, Sitong;Tang, Yijun;Li, Fengcheng
背景细胞壁和叶绿体是决定植物机械强度和籽粒产量的两种基本结构。因此，了解提高植物发育健壮细胞壁和发育良好的叶绿体的能力的机制对于农业活动是至关重要的。结果在本研究中，我们报道了一个新的水稻突变体--脆茎斑马叶(Bz1)的功能特性，该突变体表现出细胞壁成分的改变和叶绿体膜的塌陷。分子和生化分析表明，BZ1编码一个功能性的UDP-半乳糖/葡萄糖差向异构酶(UGE)，在茎和叶组织中普遍表达，并且表达水平较高。多种技术分析，包括免疫印迹、免疫金标和低温扫描电子显微镜，显示阿拉伯半乳糖蛋白(AGPs)的糖基化显著受损，并在BZ1中无序沉积纤维微纤维。脂谱分析表明，叶绿体主要糖脂--单半乳糖二酰甘油(MGDG)的含量在BZ1中显著减少。综上所述，这些结果有力地证明了BZ1参与了AGPs和MGDG糖链生物合成的UDP-半乳糖供应，从而分别导致细胞壁改变和叶绿体发育异常。由于机械强度低和光合作用降低，bz1植株表现出不利的农艺性状，而bz1高表达品系表现出促进植株生长的作用。对茎和叶的转录组分析进一步表明，参与AGPs生物合成和光合作用代谢的许多关键基因在bz1中受到显著抑制。结论BZ1是AGPs和MGDG糖基化的双靶点UGE蛋白，为培育健壮的优良作物提供了一种策略。
Background The cell wall and chloroplast are two fundamental structures determining plant mechanical strength and grain yield. Therefore, understanding mechanisms that improve plants' ability to develop a robust cell wall and well-developed chloroplast is of utmost importance for agricultural activities. Results In this study, we report the functional characterization of a novel rice mutant, brittle stem and zebra leaf (bz1), which displays altered cell wall composition and collapsed chloroplast membrane. Molecular and biochemical analysis revealed that BZ1 encodes a functional UDP-galactose/glucose epimerase (UGE) and is ubiquitously expressed with higher expression in stem and leaf tissues. Multiple techniques analyses, including immunoblots, immuno-gold, and cryogenic scanning electron microscopy, demonstrated a significantly impaired glycosylation of arabinogalactan proteins (AGPs) and disordered cellulose microfibril deposition inbz1. Lipid profiling assay showed that the amount of monogalactosyldiacylglycerols (MGDG), a major chloroplast membrane glycolipid, was significantly decreased inbz1. Taken together, these results strongly demonstrate that BZ1 participates in UDP-galactose supply for the sugar chains biosynthesis of AGPs and MGDG, which thereby, respectively, results in altered cell wall and abnormal chloroplast development. Due to inferior mechanical strength and reduced photosynthesis,bz1plants displayed detrimental agronomic traits, whereas BZ1 overexpressing lines showed enhanced plant growth. Transcriptome analysis of stems and leaves further showed that numerous key genes involved in AGPs biosynthesis and photosynthesis metabolism were substantially suppressed inbz1. Conclusions Our finding identifies BZ1 as a dual-targeting UGE protein for glycosylation of AGPs and MGDG and suggests a strategy for breeding robust elite crops.