Eriksson M, Villand P, Gardeström P, Samuelsson G
Department of Plant Physiology, Umeå University, S-901 87 Umeå, Sweden
Plant Physiol. 1998 Feb 1;116(2):637-41. doi: 10.1104/pp.116.2.637.
The time course of and the influence of light intensity and light quality on the induction of a mitochondrial carbonic anhydrase (CA) in the unicellular green alga Chlamydomonas reinhardtii was characterized using western and northern blots. This CA was expressed only under low-CO2 conditions (ambient air). In asynchronously grown cells, the mRNA was detected 15 min after transfer from air containing 5% CO2 to ambient air, and the 21-kD polypeptide was detected on western blots after 1 h. When transferred back to air containing 5% CO2, the mRNA disappeared within 1 h and the polypeptide was degraded within 3 d. Photosynthesis was required for the induction in asynchronous cultures. The induction increased with light up to 500 mumol m-2 s-1, where saturation occurred. In cells grown synchronously, however, expression of the mitochondrial CA was also detected in darkness. Under such conditions the expression followed a circadian rhythm, with mRNA appearing in the dark 30 min before the light was turned on. Algae left in darkness continued this rhythm for several days.
利用蛋白质免疫印迹法（western blot）和核酸分子杂交法（northern blot），对单细胞绿藻莱茵衣藻中线粒体碳酸酐酶（CA）的诱导过程以及光强和光质对该诱导过程的影响进行了表征。这种碳酸酐酶仅在低二氧化碳条件下（环境空气）表达。在异步生长的细胞中，从含5%二氧化碳的空气转移到环境空气后15分钟可检测到mRNA，1小时后在蛋白质免疫印迹法中检测到21-kD多肽。当转回含5%二氧化碳的空气时，mRNA在1小时内消失，多肽在3天内降解。异步培养中的诱导需要光合作用。诱导作用随着光照强度增加至500 μmol m-2 s-1时达到饱和。然而，在同步生长的细胞中，线粒体CA在黑暗中也有表达。在这种条件下，表达遵循昼夜节律，mRNA在光照开启前30分钟的黑暗中出现。置于黑暗中的藻类持续这种节律达数天。
