野生条斑紫菜(Pyropia yezoensis)叶状体对干出胁迫的抗氧化生理响应特征

Antioxidant Physiological Characteristics of Wild Pyropia yezoensis Under Desiccation Stress

中文关键词: 干出  条斑紫菜  光合  抗氧化

英文关键词: Desiccation  Pyropia yezoensis  Photosynthetic  Antioxidant

中文摘要:

      失水胁迫是野生条斑紫菜(Pyropia yezoensis)主要胁迫因子之一。为揭示条斑紫菜对失水胁迫的响应机制，本研究以2016年3月采自山东青岛湛山的野生藻体为材料，研究了失水胁迫下其光合作用和抗氧化生理响应特征。结果显示，随着失水胁迫程度的增大，PSⅡ原初光能转化效率(Fv/Fm)显著降低，在失水率60%左右时降至最低值，但复水1 h后可恢复正常值。叶绿素a (Chl a)、类胡萝卜素(Car)和可溶性蛋白(SP)含量逐渐降低，藻红蛋白(R-PE)和藻蓝蛋白(R-PC)含量先下降后上升。藻胆蛋白(R-PE+R-PC)∶SP比值的变化趋势与藻胆蛋白的变化趋势类似，但在失水率40%时上升至对照水平，失水80%时显著高于对照值。丙二醛(MDA)含量在失水率≤30%时没有显著变化，失水率≥40%时显著上升，但失水率在40%–80%时，藻体间没有显著差异。在失水率≤20%时，超氧化物歧化酶(SOD)和过氧化氢酶(CAT)的活性没有显著变化，过氧化物酶(POD)活性显著上升；随着失水率增加，3种酶的活力显著下降，低于对照组，但失水率在50%–80%时，组间没有显著差异。根据以上结果推测：失水早期，抗氧化酶SOD、CAT，尤其POD起着关键的清除自由基作用，因此，MDA含量没有明显变化；随着失水程度增加，藻胆蛋白的抗逆作用逐渐显现，为藻体在复水后快速恢复光合作用(Fv/Fm)提供保障。

英文摘要:

      Desiccation is the main abiotic stress for Pyropia yezoensis. In this study we investigated the photosynthetic and antioxidant physiological responses of a wild P. yezoensis thallus to desiccation stress, including the optimal chlorophyll fluorescence quantum yields of photosystem Ⅱ (Fv/Fm), the contents of photosynthetic pigments [chlorophyll a (Chl a), carotenoid (Car), R-phycoerythrin (R-PE), R-phycocyanin (R-PC)], soluble proteins (SPs), malondialdehyde (MDA), and the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). The results revealed that as the water loss increased, Fv/Fm decreased linearly and reached the lowest when the water loss was 60%; Fv/Fm returned to the normal level after the blades were rehydrated for 1 h. The contents of Chl a, Car, and SPs decreased gradually. The contents of R-PE and R-PC decreased when the water loss was <30% and then increased as the water loss was ≥30%. The change of phycobiliproteins/soluble proteins was similar to that of phycobiliproteins. This ratio increased to the control level when the water loss was 40% and was significantly higher than the control when the water loss was 80%. There was no significant difference in the content of MDA between the control and the blades when the water loss was ≤30%. The content of MDA increased significantly when the water loss was ≥40%. However, there was no significant difference between the blades when the water loss ranged from 40% to 80%. There was no significant change in the activities of SOD and CAT when the water loss was ≤20%. The activity of POD was significantly increased when the water loss was ≤20%. When the water loss increased to 30%, the activities of SOD, CAT and POD decreased significantly. There was no significant difference between the blades when the water loss ranged from 50% to 80%. The results above suggested that during the early stage of water loss, the antioxidant enzymes POD, CAT and SOD played key roles in scavenging the reactive oxygen species, which inhibited the yield of excessive MDA; as water loss increased, the water condition became disadvantageous for the antioxidant enzymes, and MDA was accumulated as a result. Based on the change of phycolibiprotein/SP, we speculated that the function of phycobiliproteins became more and more significant in protecting the blades against desiccation stress when the water loss was ≥30%, which could help with the rapid recovery of photosynthesis (Fv/Fm) during rehydration.