Cunningham F X, Vonshak A, Gantt E
Department of Botany, University of Maryland, College Park, Maryland 20742.
Plant Physiol. 1992 Nov;100(3):1142-9. doi: 10.1104/pp.100.3.1142.
Acclimation of the photosynthetic apparatus to changes in the light environment was studied in the unicellular red alga Porphyridium cruentum (American Type Culture Collection No. 50161). Absolute or relative amounts of four photosynthetic enzymes and electron carriers were measured, and the data were compared with earlier observations on light-harvesting components (F.X. Cunningham, Jr., R.J. Dennenberg, L. Mustárdy, P.A. Jursinic, E. Gantt [1989] Plant Physiol 91: 1179-1187; F.X. Cunningham, Jr., R.J. Dennenberg, P.A. Jursinic, E. Gantt [1990] Plant Physiol 93: 888-895) and with measurements of photosynthetic capacity. P(max), the light-saturated rate of photosynthesis on a chlorophyll (Chl) basis, increased more than 4-fold with increase in growth irradiance from 6 to 280 mueinsteins.m(-2).s(-1). Amounts of ferredoxin-NADP(+) reductase, ribulose-1,5-bisphosphate carboxylase, and cytochrome f increased in parallel with P(max), whereas numbers of the light-harvesting complexes (photosystem [PS] I, PSII, and phycobilisomes) changed little, and ATP synthase increased 7-fold relative to Chl. The calculated minimal turnover time for PSII under the highest irradiance, 5 ms, was thus about 4-fold faster than that calculated for cultures grown under the lowest irradiance (19 ms). A change in the spectral composition of the growth light (irradiance kept constant at 15 mueinsteins.m(-2).s(-1)) from green (absorbed predominantly by the phycobilisome antenna of PSII) to red (absorbed primarily by the Chl antenna of PSI) had little effect on the amounts of ribulose-1,5-bisphosphate carboxylase, ATP synthase, and phycobilisomes on a Chl, protein, or thylakoid area basis. However, the number of PSI centers declined by 40%, cytochrome f increased by 40%, and both PSII and ferredoxin-NADP(+) reductase increased approximately 3-fold on a thylakoid area basis. The substantial increase in ferredoxin-NADP(+) reductase under PSI light is inconsistent with a PSI-mediated reduction of NADP as the sole function of this enzyme. Our results demonstrate a high degree of plasticity in content and composition of thylakoid membranes of P. cruentum.
在单细胞红藻紫球藻（美国模式培养物集编号50161）中研究了光合机构对光照环境变化的适应。测定了四种光合酶和电子载体的绝对或相对含量，并将数据与早期关于捕光成分的观察结果（F.X.坎宁安，Jr.，R.J.登嫩伯格，L.穆斯塔迪，P.A.尤尔西尼克，E.甘特[1989]《植物生理学》91:1179 - 1187；F.X.坎宁安，Jr.，R.J.登嫩伯格，P.A.尤尔西尼克，E.甘特[1990]《植物生理学》93:888 - 895）以及光合能力的测量结果进行了比较。以叶绿素（Chl）为基础的光饱和光合速率P(max)，随着生长辐照度从6增加到280微爱因斯坦·米⁻²·秒⁻¹，增加了4倍多。铁氧化还原蛋白 - NADP⁺还原酶、核酮糖 - 1,5 - 二磷酸羧化酶和细胞色素f的含量与P(max)平行增加，而捕光复合体（光系统[PS]I、PSII和藻胆体）的数量变化不大，并且ATP合酶相对于Chl增加了7倍。因此，在最高辐照度下计算出的PSII最小周转时间为5毫秒，比在最低辐照度（19毫秒）下生长的培养物计算出的周转时间快约4倍。生长光的光谱组成（辐照度保持在15微爱因斯坦·米⁻²·秒⁻¹恒定）从绿色（主要被PSII的藻胆体天线吸收）变为红色（主要被PSI的Chl天线吸收），以Chl、蛋白质或类囊体面积为基础，对核酮糖 - 1,5 - 二磷酸羧化酶、ATP合酶和藻胆体的含量影响很小。然而，以类囊体面积为基础，PSI中心的数量下降了40%，细胞色素f增加了40%，PSII和铁氧化还原蛋白 - NADP⁺还原酶都增加了约3倍。在PSI光照下铁氧化还原蛋白 - NADP⁺还原酶的大幅增加与该酶仅作为PSI介导的NADP还原功能不一致。我们的结果表明紫球藻的类囊体膜在含量和组成上具有高度的可塑性。
