ALA调控干旱胁迫下黑果枸杞光合作用的生物学机制

Arid desert occupies the quite broad area in China, exhibiting the fragile ecosystem and low level of social and economic development. The significant scientific and social issues, which are needed to be solved for the arid desert, are to reduce the environmental pressure, to improve the stability of the arid desert ecosystem, and to increase the living standards of residents. As a star plant, Lycium ruthenicum contains ecological benefits of wind-proof and sand-fixing, as well as pivotal medicinal and health effects. Although Lycium ruthenicum possesses specific drought-resistance ability, its growth, especially photosynthesis, is still severely inhibited by drought, which seriously restrains the development of Lycium ruthenicum industry. Studies have shown that 5-aminolevulinic acid (ALA) can enhance the efficiency of photosynthesis in a variety of plants under drought, but the underlying regulation mechanism is still unclear. In this project, we investigate the dynamic changes of key substance content, important enzyme activity, and gene expression regulation network involved in the biosynthetic pathway of chlorophyll and heme from ALA in Lycium ruthenicum seedlings under drought stress by using physiology and molecular biology methods. It is worth noting that chlorophyll and heme are the vital components of photosynthetic system. We further explore the biological mechanism in the protective effect of exogenous ALA on the photosynthesis in Lycium ruthenicum subjected to drought. These findings will provide the theoretical guidance for improving the photosynthetic efficiency under drought, and give the scientific support for high photosynthetic efficiency breeding, cultivation technique of stress resistance, and ecological environment protection.

我国干旱荒漠区面积辽阔，该区域生态系统十分脆弱，且社会经济发展水平低下。如何既能减轻该区域的环境压力，提高干旱荒漠生态系统的稳定性，又能增加当地居民的生活水平，已成为亟待解决的重要科学问题和社会问题。黑果枸杞是我国既有防风固沙生态效益又有重要的药用和保健作用的明星植物。该植物虽有一定抗旱能力，但其生长特别是光合作用仍被干旱严重抑制，极大地阻碍了黑果枸杞产业的发展。研究表明5-氨基乙酰丙酸(ALA)可提高植物在干旱下的光合效率，但是其调控机制还待挖掘。本项目拟以黑果枸杞幼苗为材料，应用生理和分子生物学方法，阐明干旱胁迫下ALA合成光合系统重要成分叶绿素和血红素生物途径中关键物质含量、重要酶活性和基因表达调控网络方面的动态变化特征，探讨外源ALA对旱害下黑果枸杞光合系统保护效应的生物学机制。该研究将为提高干旱下植物光合作用效率提供理论指导，并为高光效育种、抗逆栽培和生态环境保护提供科学依据。

我国旱区面积辽阔，生态系统非常脆弱，且经济发展水平低下，如何既能减轻该区域的环境压力，提高旱区生态系统稳定性，又增加当地居民的生活水平，已经成为亟待解决的重要科学问题和社会问题。黑果枸杞是我国既有防风固沙生态效益又有药用和保健作用的明星植物。然而，该荒漠植物虽然有一定的抗旱能力，但是其生长特别是光合作用仍然被干旱严重抑制，极大的限制了黑果枸杞产业的发展。前期研究发现5-氨基乙酰丙酸（ALA）可以提高干旱等非生物胁迫下植物的抗逆性，特别是在光合作用方面，但是其调控机制还不清楚。本项目以黑果枸杞幼苗为实验材料，研究了外源ALA对干旱胁迫下黑果枸杞幼苗生长、光合气体交换参数、叶绿素荧光参数、抗氧化酶活性和渗透调节物质的影响。同时探索了干旱胁迫下ALA合成光合系统重要成分叶绿素和血红素生物途径中的关键物质、酶活性和基因表达的变化特征。在此基础上，利用RNA-Seq技术对干旱胁迫下及外源ALA处理后黑果枸杞幼苗进行了转录组分析，探索其分子机理。通过本项目可以得出：适宜浓度（50 mg/L）的ALA可显著提高干旱胁迫下黑果枸杞幼苗的干物质积累和净光合效率，明确了外源ALA对干旱下黑果枸杞幼苗的缓解效应，同时提高了渗透调节物质脯氨酸的含量，但是对于抗氧化酶活性无显著影响。干旱显著降低了ALA合成光合系统重要成分叶绿素和血红素的中间及最终物质，包括ALA、原卟啉IX、镁原卟啉IX、原叶绿素酸酯、叶绿素和血红素，且部分下调了编码合成酶的基因的表达；外源施加ALA显著提高了干旱胁迫下黑果枸杞幼苗叶片中这些物质的含量。转录组测序表明，干旱胁迫上调了ALA合成叶绿素途径中相关基因的表达，但是对于血红素途径没有影响。本项目从生理水平和转录组水平上，探讨了干旱胁迫下ALA调控光合作用的机制，同时明确了外源ALA对干旱下黑果枸杞的缓解效果，为通过栽培技术和基因工程技术提高黑果枸杞抗旱性提供了理论基础，也为进一步应用ALA提高农业生产水平，缓解生态环境恶化等方面提供了指导。