pH对坛紫菜丝状体光合速率和无机碳利用的短时效应

Effects of pH on CO_2 Concentrating Mechanism of Pyropia haitanensis Conchocelis

为了评估保种丝状体在长期碱化(高pH/低[CO_2])后,其CO_2浓缩机制(CO_2concentrating mechanism,CCM)能否快速响应CO_2浓度([CO_2])的变化,分析了丝状体的无机碳吸收利用途径对低pH/高[CO_2]的响应规律。结果表明:丝状体CCM的主要组分是胞外碳酸酐酶(CA)、胞内CA和HCO_3^-转运蛋白。在保种条件(pH=9)下,胞外CA对净光合速率的贡献达到80%;而在正常海水(pH=8)中,胞外CA和HCO_3^-转运蛋白对光合作用的贡献分别为45%和31%,二者差异不明显;当pH值降低到8时光合速率显著增加了74%,胞内CA的贡献显著增加。随着pH值的下降,CCM和光合固碳相关基因都受到显著抑制。本研究表明,即使经过长时间的高pH培养,坛紫菜丝状体依然能快速地在生理和分子水平响应低pH/高[CO_2]。

Generally,algae apply C02concentrating mechanism(CCM)to effectively obtain inorganic carbon,and knowledge is limited on CCM of Pyropia haitanensis conchocelis.To evaluate the effects of long-term seawater alkalization(high pH/low[C02])on CCM of conchocelis,this study investigated the response of absorption pathways of inorganic carbon to low pH/high[C02].Our results showed that,the major components of CCM of conchocelis were the extracellular carbonic anhydrase(CA)and intracellular CA,and the H C03transporter.Under sustain conditions(pH=9),the contribution of extracellular CA to net photosynthetic rate was80%.However,in normal seawater(pH=8),the extracellular CA and H C03~transporter respectively contributed45%and31%,and no significant difference was found between them.The decrease of pH from9to8significantly increased the photosynthesis by74%,and meanwhile the contribution of intracellular CA significantly increased.Low pH inhibited the expression of key genes of CCM and carbon fixation.The study found that,even after long-term incubation in seawater at pH=9,the conchocelis still could respond quickly at physiological and molecular levels.