高盐胁迫对坛紫菜(Pyropia haitanensis)叶状体光合作用的影响

The Effect of Hypersaline Stress on Photosynthesis of Pyropia haitanensis

坛紫菜(Pyropia haitanensis)具有极强的耐高盐胁迫能力,但其耐盐机理尚不明确。检测了不同高盐(100、110)胁迫处理不同时间(0,4,8,24 h)时坛紫菜Z-61藻体的最大光化学效率( F v/ F m)和净光合作用,并选取高盐胁迫4 h后的藻体提取RNA,采用第二代高通量测序技术分析正常盐度(对照组,30)与高盐胁迫处理的坛紫菜叶状体转录组数据,探究坛紫菜响应高盐胁迫过程中的光合生理机制。结果发现:盐度100对坛紫菜藻体 F v/ F m无显著影响;而盐度110下,藻体 F v/ F m逐渐下降至0,但转移至对照海水后其仍能恢复到初始水平,可将110称之为“亚致死”(sub-lethal)盐度;当盐度增加至120时,藻体 F v/ F m急剧下降至0,且转移到对照海水中不能恢复,即120是致死的盐度。转录组数据显示,高盐胁迫下的转录本与对照组有很大差异,光合作用相关基因在高盐胁迫下显著上调表达,包括多条碳酸酐酶基因和天线蛋白基因,并且在盐度100胁迫下其上调趋势更为明显。以上结果说明:坛紫菜在耐受盐度100条件下可以通过积极提高光合作用相关基因的表达,维持光合活性,为藻体生长提供物质和能量;而在亚致死盐度110条件下,坛紫菜光合活性逐渐下降,光合基因表达受到抑制,活性氧的产生减少,避免藻体细胞遭受过氧化损伤。这说明坛紫菜可以通过积极响应调节光合系统来应答高盐胁迫。

Although Pyropia haitanensis has stronger capacity to resist hypersaline stress,the underlying mechanism is still unclear.In the present study,the effects of hypersaline (100 and 110) stresses on the maximum photochemical efficiency ( F v/ F m),net photosynthetic rate and comparative transcriptome analysis of P.haitanensis thalli were studied in order to explore photosynthetic mechanism of the P.haitanensis thalli at different time period(0,4,8,and 24 h) of hypersaline stress.The results revealed that 100 salinity had no significant effect on the F v/ F m of P.haitanensis ,while the F v/ F m gradually decreased to 0 under the 110 salinity,but it could still return to the initial level after transferring to the control seawater.More seriously,the F v/ F m of P.haitanensis fell to 0 and could not be recovered when the salinity increased to 120.Therefore,we refer to 110 as a “sub-lethal” salt concentration and 120 as a lethal salt concentration.Transcriptome analysis showed that there was obvious difference between hypersaline stress and control group.The genes involved in the photosynthetic metabolic pathway were up-regulated under high salt stress,including multiple carbonic anhydrase and antenna proteins-related genes.Moreover,the up-regulated trend was more obvious at 100.All the results above showed that P.haitanensis was able to maintain photosynthetic activity,and provide material and energy for growth by actively increasing the expression of photosynthesis-related genes under 100.However,in order to reduce the production of reactive oxygen species and avoid the cell from being damaged by peroxidation,the photosynthetic activity of P.haitanensis gradually decreased and the photosynthetic genes expression was inhibited.This indicated that P.haitanensis could respond to high salt stress by actively responding to photosynthetic systems.This study provided a new idea and theoretical basis for clarifying the mechanism of high salt tolerance in P.haitanensis .