Institute of Plant Physiology, Biological Research Center, Hungarian Academy of Sciences, Szeged, P.O. Box 521, H-6701 Hungary.
Plant Physiol. 1991 Apr;95(4):997-1003. doi: 10.1104/pp.95.4.997.
Diurnal fluctuations were observed in the content and some structural and functional properties of the light-harvesting chlorophyll (Chl) a/b pigment-protein complex of photosystem II (LHCII) in young developing wheat (Triticum aestivum) leaves grown under 16 hours light/8 hours dark illumination regime. The fluctuations could be correlated with the diurnal oscillation in the level of mRNA for LHCII. The most pronounced changes occurred in the basal segments of the leaves. They were weaker or hardly discernible in the middle and tip segments. As judged from the diurnal variations of the Chl-a/Chl-b molar ratio, the LHCII content of the thylakoid membranes peaked around 2 pm. This can be accounted for by the cumulative effect of the elevated level of mRNA in the morning and early afternoon. In the basal segment, the extent of the fluctuation in the LHCII content was approximately 25%, as determined from gel electrophoresis ("green gels"). The amplitude of the principal bands of the circular dichroism (CD) spectra of isolated chloroplasts paralleled the changes in the LHCII content. Our circular dichroism data suggest that the newly synthesized LHCII complexes are incorporated into the existing helically organized macrodomains of the pigment-protein complexes or themselves form such macrodomains in the thylakoid membranes. Chl-a fluorescence induction kinetics also showed diurnal variations especially in the basal segments of the leaves. This most likely indicates fluctuations in the ability of membranes to undergo "state transitions." These observations suggest a physiological role of diurnal rhythm of mRNA for LHCII in young developing leaves.
在 16 小时光照/8 小时黑暗的光照制度下生长的年轻小麦（Triticum aestivum）叶片中，观察到光捕获叶绿素（Chl）a/b 色素蛋白复合物 II（LHCII）的含量和一些结构及功能特性的日变化。这种波动可以与 LHCII mRNA 水平的日振荡相关联。最明显的变化发生在叶片的基部。在中部和顶端部分，变化较弱或几乎难以察觉。从叶绿素 a/叶绿素 b 摩尔比的日变化来看，类囊体膜中的 LHCII 含量在下午 2 点左右达到峰值。这可以归因于上午和下午早些时候 mRNA 水平升高的累积效应。在基部，LHCII 含量的波动幅度约为 25%，这是通过凝胶电泳（“绿色凝胶”）确定的。分离叶绿体圆二色性（CD）光谱的主带振幅与 LHCII 含量的变化平行。我们的圆二色性数据表明，新合成的 LHCII 复合物被整合到现有的色素蛋白复合物的螺旋组织的宏观结构中，或者自身在类囊体膜中形成这种宏观结构。叶绿素 a 荧光诱导动力学也显示出日变化，特别是在叶片的基部。这很可能表明膜经历“状态转变”的能力波动。这些观察结果表明，年轻发育叶片中 LHCII mRNA 的日节律具有生理作用。
