坛紫菜紫外吸收物质类菌孢素氨基酸的世代差异特征

The Generation Difference of UVR Absorbing Compounds Mycosporine-like Amino Acids (MAAs) of Pyropia haitanensis

经济海藻坛紫菜(Pyropia haitanensis)的生活史是异型世代交替的。坛紫菜不同世代所处的紫外辐射(UVR)环境差异很大,有必要研究不同世代在紫外辐射耐受机制方面的差异。以坛紫菜高产品系Z-61为材料,测定并分析了坛紫菜紫外吸收物质的世代差异,发现紫外吸收物质类菌孢素氨基酸(MAAs)在叶状体中的含量是丝状体的6倍。还克隆获得了两条MAAs合成关键基因的全长序列,分别命名为PharoB-1和PharoB-2。通过系统进化树分析显示,PharoB-1和PharoB-2的编码蛋白分别与微藻和高等植物亲缘关系较近。两条基因在叶状体世代的表达水平均要显著高于丝状体世代,与坛紫菜MAAs含量的世代差异一致,这种差异可能与坛紫菜不同世代的紫外辐射环境直接相关。

The heteromorphic life history of economic seaweed Pyropia haitanensis includes a gametophytic thallus stage and a shell-living conchocelis stage. The ultraviolet radiation（UVR） dosage in the growth environment of thallus is significantly higher than that of conchocelis. This study found that the MAAs content of P. haitanensis thalli was higher than that of conchoceli. Two key enzyme genes involved in synthetizing MAAs were cloned and named as PharoB-1 and PharoB-2. The results of this study revealed that the amino acid sequences of PharoB-1 and PharoB-2 classified in the same cluster with microalgae and higher plants,respectively. Both PharoB-1 and PharoB-2 in thallus stage showed significantly higher expression levels than in that of conchocelis stage. The results of gene expressions are consistent with the physiological performance and could be attributed to that the UVR dosage in the growth environment of thallus is higher than that of conchocelis.