条斑紫菜突变体“Py_MR2”对高光和低氮磷胁迫的生理生化响应

The effects of high light stress and low nitrogen and phosphorus stress on the physiological and biochemical characteristics of the mutant

关键词:  低氮磷胁迫  高光胁迫  光合作用  碳代谢  氮代谢

Key words:  Porphyra yezoensis  High light stress  Low nitrogen and phosphorus stress  Biochemical components  Chlorophyll fluorescence parameters    

摘要:

本研究旨在解析条斑紫菜突变株Py_MR2与野生型Py_CW对高光、低氮磷及其复合胁迫的适应机制差异，为耐逆品种选育提供理论依据。通过设置对照组[60 μmol photons/(m2·s)、5 mg/L NO3?-N、0.5 mg/L PO43?-P]及三种胁迫组（高光、低氮磷、双重胁迫）测定两品系的叶绿素荧光参数、光合色素含量、抗氧化物质及碳氮磷代谢酶活性，发现：（1）高光与双重胁迫显著降低两品系Fv/Fm、Y(II)、Rubisco及氮磷代谢酶（NR、ACP/AKP）活性，但诱导Y(NPQ)升高，表明PSII功能受损但光保护机制被激活。（2）低氮磷胁迫下两品系维持较高Fv/Fm、Y(II)和Chl-a，显示较强耐受性；同时藻红蛋白PE和藻蓝蛋白PC含量下降并伴随磷酸酶（ACP/AKP）活性显著提升，而硝酸还原酶NR活性稳定，提示紫菜优先通过增强磷代谢应对复合营养限制，可能与其藻胆蛋白作为氮储备有关。（3）Py_MR2在胁迫下呈现显著代谢优势：四组处理中藻胆蛋白、Chl-a、还原型谷胱甘肽GSH含量及Rubisco、超氧化物歧化酶SOD、过氧化氢酶CAT活性均高于Py_CW；高光下PE、PC含量逆势增加，低氮磷时Fv/Fm和类胡萝卜素上升，且Rubisco与双磷酸酶协同上调。相较之下，Py_CW主要依赖还原型抗坏血酸ASA和糖代谢相关酶响应胁迫。结果表明Py_MR2通过多途径协同调控（增强光能利用效率、抗氧化防御及氮磷代谢灵活性）展现出更优的胁迫适应能力，为耐逆品系选育提供了理论依据。

Abstract:

The mutant strain "Py_MR2" and the wild type "Py_CW" of Porphyra yezoensis obtained in the early stage of the laboratory were used as research objects to explore their physiological and biochemical responses to high light and low nitrogen and phosphorus stress. With 60 μmol photons/(m2 s), 5 mg/L NO3-1-N, and 0.5 mg/L PO4-3-P as the control group, the high light stress group was set up as 300 μmol photons/(m2 s), 5 mg/LN, and 0.5 mg/LP, the low nitrogen and phosphorus stress group was set up as 60 μmol photons/(m2 s), and the high light and low nitrogen and phosphorus double stress group was set up as 300 μmol photons/(m2 s), without adding N and P. The results showed that: (1) Under high light and dual stress, the activities of Fv/Fm, Y (II), Rubisco, nitrate reductase (NR), acid phosphatase (ACP), and alkaline phosphatase (AKP) decreased in both strains, while Y (NPQ) increased significantly, indicating that high light stress led to a decrease in PSII photosynthetic activity and N and P absorption and assimilation capacity, but the algae had a certain light protection ability. (2) Under low nitrogen and phosphorus stress, the Fv/Fm, Y (II), and chlorophyll a (Chl-a) contents of both strains were higher than those of the high light stress group, indicating that they had a higher tolerance to low nitrogen and phosphorus stress. At the same time, the contents of phycoerythrin (PE) and phycocyanin (PC) decreased significantly, and the activities of ACP and/or AKP increased significantly, while the activity of NR did not change significantly, indicating that when N and P were both scarce in the environment, Porphyra yezoensis more actively regulated the inorganic P transformation pathway, which should be related to the high level of phycobiliprotein, a nitrogen pool, in Porphyra. (3) Among the four groups, the contents of phycobiliprotein, Chl-a and GSH, as well as the activities of Rubisco, SOD and CAT in Py_MR2 were significantly higher than those in Py_CW, while the ASA content and the activities of fructose-6-phosphate kinase and glutathione reductase in Py_CW were significantly higher than those in Py_MR2. This indicates that there are significant metabolic differences and stress responses between the two strains. Under high light, the contents of PE and PC increased significantly in Py_MR2 and decreased significantly in Py_CW; under low nitrogen and phosphorus, the contents of Fv/Fm and carotenoids increased in Py_MR2 and decreased significantly in Py_CW, and the activities of Rubisco, ACP and AKP in Py_MR2 were significantly upregulated, while only AKP was upregulated in Py_CW. In summary, compared with Py_CW, Py_MR2 showed higher stress tolerance. This study laid a foundation for the cultivation of new strains of Porphyra yezoensis and the optimization of marine cultivation.