沙蓬表皮毛减少突变体Astcl1的克隆及其对不同干旱自然环境的适应性研究

The Amaranthaceae species, Agriophyllum squarrosum, is an annual psammophyte adapted to mobile sand dunes in arid and semi-arid regions of China. The extreme stress tolerance and high nutritional value of A. squarrosum make it attractive for use as an alternative crop in response to concerns about climate change and food security. The aerial tissues of A. squarrosum are covered with dense trichomes, however, this adaptation trait negatively affects the final seed harvest. An ethyl methanesulfonate (EMS) induced Agriophyllum squarrosum trichomeless1 mutant (Astcl1) has been isolated and genetic analysis have revealed that phenotype variation is controlled by a single recessive locus. Here, the phenotype variation of the Astcl1, including trichome development, cuticle formation, and leaf water loss rate, will be examined in detail. A combination of bulked segregant RNA-sequencing (BSR-seq) and conventional linkage analysis will be employed to fine map and target the mutation underlying the phenotype of the Astcl1. The expression pattern of the Astcl1 will be determined in various organs and under drought treatments and gene expression profiles across different tissues will be analyzed between wild type and Astcl1 plants to illustrate the molecular mechanism of how Astcl1 controls the trichome development in A. squarrosum. Transgenic plants will also be constructed to validate the function of the Astcl1 in tobacco. Furthermore, the eco-physiological performance of Astcl1 plants under natural precipitation and artificial irrigation conditions will be examined at two different experiment stations (Shapotou and Gaolan) in arid region, and the feasibility of the Astcl1 plant as a single-trait-domesticated cultivar will be finally evaluated. The implementation of this project will significantly deepen our understanding of the development mechanism and eco-physiological function of trichomes in desert plants and may provide a new germplasm for domestication breeding of A. squarrosum.

一年生苋科藜亚科植物沙蓬主要分布于我国干旱半干旱区流动沙丘上，耐逆性极强，种子营养全面，可作为一种潜势作物以应对气候变化对粮食安全的影响。沙蓬表面密被表皮毛，这种适应性状严重影响种子采集。通过甲基磺酸乙酯诱变，我们获得一株表皮毛减少突变体Astcl1，其表型变异由隐性单基因突变控制。本项目拟系统比较Astcl1表皮毛发育和角质层形成等表型变异，明确其耐旱性；联合转录组混池测序和遗传作图，准确定位和克隆目的基因，解析该基因的时空表达和干旱胁迫响应模式，挖掘其调控和蛋白互作网络，进一步构建烟草转基因植株验证其生物学功能，揭示Astcl1调控表皮毛形成的分子机制。与此同时，观测自然降水和人工灌溉条件下Astcl1植株在干旱区不同自然环境中的适应性，评估其作为单一驯化性状栽培品系的可行性。本项目的实施将为认知沙漠植物表皮毛发育机制和生理生态功能提供理论依据，同时也为沙蓬驯化育种提供创新遗传资源。

本项目旨在克隆沙蓬表皮毛减少突变体astcl1的遗传控制基因，明确astcl1株系在不同干旱环境中的生理生态适应性，以及评估其作为诱变育种候选材料的可行性。沙蓬表皮毛在植株生长的中后期易脱落，暗示其具有发育阶段特异的生理生态功能。astcl1突变严重影响表皮毛的起始和气孔的早期形成，在不同生长阶段astcl1叶片保水性的表型变异是由表皮毛、气孔、角质层协同调控的。利用测序定位和图位克隆，项目组确认了油菜素内酯信号通路的丝氨酸/苏氨酸蛋白磷酸酶BSL1是astcl1突变体的目的基因，并利用作图群体随机测序、M5分离群体混池测序和等位突变体筛选等方法验证了基因克隆结果。差异基因分析表明astcl1突变导致角质层合成相关基因异常表达。此外，通过3年两个野外台站的栽培发现astcl1和野生型植株均可完成生活史，表型差异主要体现在种子粒径、千粒重、结实率、单株产量和收获指数等关键农艺性状上。进一步采用非靶向代谢组学分析沙地和黄土地收获的种子发现，基因型差异直接影响的化合物只有254个，说明astcl1突变只影响了小部分氨基酸合成代谢相关的营养组分。沙蓬种子代谢物的丰度变异也存在基因型依赖和非基因型依赖的可塑性响应机制。总之，astcl1株系在不同栽培方式和种植地都呈现出种子粒径和千粒重显著增大，且种子萌发整齐、速率快，具有良好的育种潜力，可作为单一驯化性状栽培株系在沙地开展栽培。本项目的执行实现了沙蓬诱变选育株系在沙地和黄土地的引种栽培，明确了利用人工诱变开展沙蓬从头驯化，快速培育栽培品系的可行性。