低温胁迫影响坛紫菜多糖动态变化与代谢调控机制研究

Porphyra haitanensis is an evolutionally special eukaryotic red algae species which is specifically cultivated in China because of its economic importance. Previous studies found that when the number of times for harvest increased, the seawater temperature decreased and gradual alterations in the content and structure of various carbohydrates were observed, suggesting the existence of some adaptive mechanism prevent the red algae from the damage caused by low temperature. However, this potential mechanism remains unexplored. Taking advantage of the Zhejiang Laver Breeding Base, this study is aimed to explore the sugar metabolism-related genes in P.haitanensis. In our study, red algae samples harvested at different time periods will be subjected to cold stress and then transcriptome analysis, and in aspects of sugar content and structure, cellular psychology and biochemistry, and RNA transcription, we will explored the factors that influence the major conversion mechanism of carbohydrate metabolism decomposition, the post-sugar-decomposition redistribution mechanism of secondary carbon resource, and the sugar allocation and accumulation. Furthermore, the glucose metabolism- and transportation-related genes in the red algae and their expression patterns will be investigated in this study to reveal the sugar mediated protective mechanism responding to low temperature. This project will establish a foundation of quality evaluation for P. haitanensis breeding, expand the knowledge of the biological mechanism of photosynthetic carbon metabolism, and provide guidance for cultivation and high-value utilization of P. haitanensis.

坛紫菜是一种进化地位特殊的真核红藻，也是我国特有的人工栽培种，具有重要经济价值。前期研究发现，随着采收次数增加，养殖区域海水温度逐渐降低，同时不同类型糖含量与结构逐渐发生变化，揭示其体内必然存在某些保护性适应机制，以有效避免低温环境对其造成的损害。目前低温环境影响坛紫菜体内糖物质的生理调控机制尚不清楚。本项研究将依托于浙江坛紫菜养殖基地，以坛紫菜中糖代谢相关基因的发掘为主要目标，以低温胁迫处理叶状体为参照对象，通过转录基因组学分析技术，分别从糖成分与结构、细胞生理生化、分子转录水平探索坛紫菜细胞糖代谢主要转换机制之间的影响因素、糖分解后的二次碳源重新分配机制以及糖的分配与积累，发掘糖代谢与转运相关基因及其表达规律，揭示糖介导的坛紫菜抗低温应答机制。本项目的实施将为完善养殖坛紫菜品质评价体系奠定基础，丰富和拓展对光合生物碳代谢机制的认识，同时对坛紫菜的栽培实践和高值化利用有重要的指导意义。

坛紫菜中糖含量占其干重的比例高达35-50%，糖代谢是贯穿其整个生活史的核心代谢过程，阐明坛紫菜应答低温胁迫的糖代谢调控机制具有重要意义。本研究以坛紫菜中糖代谢相关基因的发掘为主要目标，以不同低温胁迫同种生活阶段的叶状体为研究对象，通过转录基因组学分析技术，分别从多糖成分与结构、藻体生理生化、分子转录水平探索坛紫菜细胞糖代谢主要转换机制和动态变化规律。研究发现，从一水到六水不同采收期坛紫菜中的纤维素含量逐渐增加，红藻淀粉含量则先增加后减少，蛋白质和半乳聚糖的含量则逐渐降低至稳定状态。半乳聚糖硫酸酯的总糖含量逐渐降低，3,6-内醚半乳糖含量逐渐增加，D-半乳糖甲基化程度增加。以“浙东一号”叶状体作为实验材料，随着低温胁迫时间延长，坛紫菜的相对生长速率逐渐下降，藻体均表现出分枝减少，颜色变浅等症状。透射电镜显示，细胞内出现较多的红藻淀粉颗粒，色素体板层结构较为模糊，有明显的肿胀现象。在低温胁迫的样本中鉴定出了一系列与糖代谢有关的差异表达基因，进行了转录水平分析，参与以下糖代谢相关的pathways，分别为糖酵解/糖异生、柠檬酸循环（TCA循环）等多条路径。筛选并分析了淀粉和蔗糖代谢、果糖和甘露糖代谢、半乳糖代谢、戊糖和葡萄糖醛酸的相互转化相关的富集差异基因11条，初步阐释了坛紫菜对低温胁迫应答的分子机制。发表论文8篇（其中SCI收录4篇），申请发明专利3项（其中1项获授权）。