Department of Chemistry, Umeå University, 90187, Umeå, Sweden.
Botany Department, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada.
Photosynth Res. 2018 Mar;135(1-3):149-163. doi: 10.1007/s11120-017-0400-0. Epub 2017 May 24.
Plants and algae have developed various light-harvesting mechanisms for optimal delivery of excitation energy to the photosystems. Cryptophyte algae have evolved a novel soluble light-harvesting antenna utilizing phycobilin pigments to complement the membrane-intrinsic Chl a/c-binding LHC antenna. This new antenna consists of the plastid-encoded β-subunit, a relic of the ancestral phycobilisome, and a novel nuclear-encoded α-subunit unique to cryptophytes. Together, these proteins form the active αβ·αβ-tetramer. In all cryptophyte algae investigated so far, the α-subunits have duplicated and diversified into a large gene family. Although there is transcriptional evidence for expression of all these genes, the X-ray structures determined to date suggest that only two of the α-subunit genes might be significantly expressed at the protein level. Using proteomics, we show that in phycoerythrin 545 (PE545) of Guillardia theta, the only cryptophyte with a sequenced genome, all 20 α-subunits are expressed when the algae grow under white light. The expression level of each protein depends on the intensity of the growth light, but there is no evidence for a specific light-dependent regulation of individual members of the α-subunit family under the growth conditions applied. GtcpeA10 seems to be a special member of the α-subunit family, because it consists of two similar N- and C-terminal domains, which likely are the result of a partial tandem gene duplication. The proteomics data of this study have been deposited to the ProteomeXchange Consortium and have the dataset identifiers PXD006301 and 10.6019/PXD006301.
植物和藻类已经发展出各种不同的光捕获机制，以将激发能最佳地传递到光系统。隐藻已经进化出一种利用藻胆体色素来补充膜内在的 Chl a/c 结合 LHC 天线的新型可溶性光捕获天线。这种新天线由质体编码的β亚基组成，这是祖先藻胆体的遗迹，以及一种独特的核编码的α亚基，这是隐藻所特有的。这两种蛋白共同构成了活性的αβ·αβ四聚体。在迄今为止研究的所有隐藻中，α亚基已经发生了复制和多样化，形成了一个庞大的基因家族。尽管有转录证据表明所有这些基因都有表达，但到目前为止确定的 X 射线结构表明，只有两个α亚基基因可能在蛋白质水平上得到显著表达。通过蛋白质组学，我们发现在具有测序基因组的隐藻中，当藻类在白光下生长时，PE545（PE545）中的所有 20 个α亚基都有表达。每种蛋白质的表达水平都取决于生长光的强度，但在应用的生长条件下，没有证据表明α亚基家族的各个成员存在特定的光依赖性调节。GtcpeA10 似乎是α亚基家族的一个特殊成员，因为它由两个相似的 N-和 C-末端结构域组成，这可能是部分串联基因复制的结果。本研究的蛋白质组学数据已被提交给 ProteomeXchange 联盟，并具有数据集标识符 PXD006301 和 10.6019/PXD006301。
