| 摘要: |
| 镉是广泛存在于水生生态系统的毒害痕量金属,污染水体中痕量金属对水生生物的影响十分重要。光合作用是微藻生长发育的核心过程，Lhc基因家族参与捕光及非光化学淬灭过程，其包括Lhca和Lhcb亚家族,编码蛋白质构成光合系统捕光复合体。本研究从本实验室组装的杜氏盐藻基因组中鉴定了4条Lhca与7条Lhcb基因，通过多序列比对、蛋白质三维结构及保守结构域预测分析其含有保守的Lhc基序。系统发育树表明，杜氏盐藻与部分微藻及高等植物的Lhc基因聚类相近，且高度保守。q-PCR分析表明,不同镉浓度处理下,Lhc基因表达水平在24 h时，Lhcb2.3无显著变化，Lhca1、Lhcb2.1、Lhcb7除2500 μg/L组均表达下调，Lhca5.1、Lhcb4除25 μg/L组均表达下调，其他所有组均表达下调；96 h全部基因均表达上调。Lhcb2.2与Lhcb7基因在镉胁迫下的表达特征最突出并具一定代表性。杜氏盐藻生长曲线、光合效率及各色素测定结果表明，光合效率对镉浓度变化十分敏感，高浓度镉显著抑制杜氏盐藻生长，叶绿素a及总类胡萝卜素含量随镉浓度的升高呈先降低后升高最后降低的趋势变化。β-胡萝卜素含量在细胞不同生长阶段根据镉胁迫程度表现出时间依赖效应。该研究深入挖掘了杜氏盐藻Lhc家族基因，为深入研究水体金属污染对杜氏盐藻的影响奠定了基础。 |
| 关键词: 杜氏盐藻 镉 Lhc基因家族 光合作用 |
| DOI：10.11693/hyhz20240500118 |
| 分类号: |
| 基金项目:国家自然科学基金项目 |
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| Identification of the Lhc gene family in Dunaliella salina and its expression response under different cadmium concentrations |
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WU Ming-Xu, XIAO Jia-Yuan, CHEN Tian-Hong, ZHU Qing-Ling
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Zhejiang Ocean University
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| Abstract: |
| Cadmium is a toxic metal widely distributed in aquatic ecosystems. Trace metals in contaminated water are very important to aquatic organisms. At the photosynthetic level, the sensitive response of Dunaliella salina to trace metal cadmium has the potential to be exploited for monitoring and screening of metal pollution in marine ecosystems. Photosynthesis is the core process of microalgae growth and development, and the Lhc gene family actively participates in light harvesting and non-photochemical quenching processes, including Lhca and Lhcb subfamilies. The proteins encoded by them constitute the light harvesting complex in PSI and PSII, which together constitute the light harvesting antenna of microalgae photosynthetic system. 4 Lhca and 7 Lhcb genes were identified from the genome of Dunaliella salina assembled in our laboratory. In this study, we found that they contain conserved Lhc motifs and chlorophyll binding amino acid residues through multiple sequence alignment, 3D structure prediction and conserved domain analysis. The constructed phylogenetic analysis showed that Dunaliella salina Lhc gene is similar to some microalgae and higher plant clusters, indicating that the Lhc gene is highly conserved. Q-PCR analysis showed that Lhc gene expression levels had no significant change at 24 h under different cadmium concentrations, but were down-regulated in Lhca1, Lhcb2.1 and Lhcb7 groups except 2500 μg/L, and down-regulated in Lhca5.1 and Lhcb4 groups except 25 μg/L. The other 5 genes were down-regulated in all groups; All genes were up-regulated at 96 h. The expression characteristics of Lhcb2.2 and Lhcb7 genes under cadmium stress are the most prominent and representative, which can be used as markers for environmental monitoring.The results of measuring the growth curve, chlorophyll fluorescence parameters and pigments of Dunaliella salina showed that the photosynthetic efficiency of Dunaliella salina was very sensitive to the change of cadmium concentration, and the growth of Dunaliella salina was significantly inhibited by high cadmium concentration. The contents of chlorophyll a and total carotenoid decreased first, then increased and finally decreased with the increase of cadmium concentration. The content of β-carotene showed a specific time-dependent effect according to the degree of cadmium stress in a certain growth stage of cells. In this study, the Lhc family genes of Dunaliella salina were deeply excavated, which laid a theoretical foundation and provided a certain reference for the effect of metal pollution on Dunaliella salina. |
| Key words: Dunaliella salina cadmium Lhc gene family photosynthesis |