硅藻适应铁限制海区环境机制中铁载体的作用解析

Primary productivity is seriously restricted by low iron concentration, being one of the most important factors. In order to survive, organisms could enhance the absorption of iron by synthesis of iron strong chelating substances such as siderophores. Marine diatoms have unique abilities to be adapted to iron restricted environment. However, it is not clear whether siderophore is existed in diatoms. Based on mining of the sequenced diatom genomes, diatoms may also produce siderophores that would play important roles. In this study, by comparison of the two diatoms with quite different abilities of tolerance to low iron concentration (Phaeodactylum tricornutum and Thalassiosira pseudonana), followed by bioinformatics analysis and heterologous expression, we intend to find the potential siderophores in these diatoms. Then by using the gene editing technology, the biosynthesis pathway of siderophores would be elucidated. By exploration of its intracellular mechanism of absorption and transport of, the roles of these siderophores in the responses of different diatoms to iron deficiency would be revealed at the physiological level. By comparing the two types of marine diatoms with different tolerances and adaptations to iron limitation, it would help us to understand their distributions of different diatoms in natural sea water with different iron levels.

低铁环境是限制初级生产力的最重要因素之一，生物可通过合成铁强螯合物质（如铁载体siderophore）等增强对铁元素的吸收摄入，海洋硅藻对铁限制海区环境有其独特的适应能力，但对其是否存在此种机制还不清楚。基于前期对已知硅藻基因组的信息挖掘，表明硅藻可能产生铁载体并在其应对低铁胁迫时起到重要作用，本项目拟以耐受低铁能力差异显著的两种硅藻（三角褐指藻和假微型海链藻）为研究材料，通过生物信息学手段结合异源表达系统挖掘并比较不同硅藻中潜在的铁载体，进而利用基因编辑技术验证其生物合成途径相关基因功能并初步探索其在细胞内的吸收转运机制，最终在生理水平上解析铁载体在不同硅藻应对低铁胁迫中的作用。挖掘出相应的铁载体并阐明它们在硅藻应对低铁胁迫机制中作用，是阐明硅藻不同种属间耐受低铁能力差异的生物学基础、解析硅藻适应铁限制环境生理生态学机制的重要工作，将为进一步解释海区环境变化如何影响硅藻分布和多样性水平。

低铁环境是限制初级生产力的最重要因素之一，生物可通过合成铁强螯合物质增强对铁元素的吸收摄入，海洋硅藻对铁限制海区环境有其独特的适应能力，但对其是否存在此种机制还不清楚。本研究通过对已知硅藻基因组的信息挖掘，发现了基于非核糖体肽合酶的次生代谢生物合成途径，结合异源表达分析酶学性质，表明其很可能以L-天冬酰胺为天然底物，推测了可能合成的次生代谢产物，进而利用基因编辑技术验证其生物合成途径相关基因功能，并初步挖掘了其在低铁胁迫条件下生物合成途径调控相关的转录因子，为最终在生理水平上解析铁螯合次生代谢产物在硅藻应对低铁胁迫中的作用奠定基础。挖掘出相应的铁载体并阐明它们在硅藻应对低铁胁迫机制中作用，是阐明硅藻不同种属间耐受低铁能力差异的生物学基础、解析硅藻适应铁限制环境生理生态学机制的重要工作，将为进一步解释海区环境变化如何影响硅藻分布和多样性水平。