García-Cerdán José G, Sveshnikov Dmitry, Dewez David, Jansson Stefan, Funk Christiane, Schröder Wolfgang P
Department of Chemistry, Umeå University, Sweden.
Plant Cell Physiol. 2009 Feb;50(2):191-202. doi: 10.1093/pcp/pcn188. Epub 2008 Dec 26.
PSII, the oxygen-evolving complex of photosynthetic organisms, contains an intriguingly large number of low molecular weight proteins. PsbX, one of these proteins, is ubiquitous in PSII complexes of cyanobacteria and plants. In previous studies, deletion of the PsbX protein in cyanobacteria has not resulted in clear phenotypic changes. Here we report the construction of an antisense (AS-PsbX) line in Arabidopsis thaliana with <10% of wild-type PsbX levels. AS-PsbX plants are capable of photoautotrophic growth, but biochemical, biophysical and immunological evidence demonstrates that reduction of PsbX contents leads to reduced levels of functional assembled PSII core complexes, while the light-harvesting antennae are not affected. In addition, levels of phosphorylation of the core proteins D1, D2 and CP43 are severely reduced in the antisense plants relative to their wild-type counterparts. We conclude that PsbX is important for accumulation of functional PSII.
光系统II（PSII）是光合生物中负责放氧的复合体，含有数量惊人的低分子量蛋白质。PsbX就是其中一种蛋白质，它在蓝细菌和植物的PSII复合体中普遍存在。在之前的研究中，蓝细菌中PsbX蛋白的缺失并未导致明显的表型变化。在此我们报道了在拟南芥中构建的一个反义（AS-PsbX）株系，其PsbX水平低于野生型的10%。AS-PsbX植株能够进行光合自养生长，但生化、生物物理和免疫学证据表明，PsbX含量的降低导致功能性组装的PSII核心复合体水平下降，而捕光天线未受影响。此外，与野生型植株相比，反义植株中核心蛋白D1、D2和CP43的磷酸化水平严重降低。我们得出结论，PsbX对功能性PSII的积累很重要。
