Plant Molecular Biology, Department of Biology I, Ludwig-Maximilians-Universität München, 82152 Planegg-Martinsried, Germany; Copenhagen Plant Science Center, University of Copenhagen, 1871 Frederiksberg C, Denmark; Research and Innovation Center, Fondazione Edmund Mach, via E. Mach 1, 38010 San Michele all'Adige, Italy.
Copenhagen Plant Science Center, University of Copenhagen, 1871 Frederiksberg C, Denmark.
Mol Plant. 2017 May 1;10(5):721-734. doi: 10.1016/j.molp.2017.02.009. Epub 2017 Mar 10.
Plants contain various factors that transiently interact with subunits or intermediates of the thylakoid multiprotein complexes, promoting their stable association and integration. Hence, assembly factors are essential for chloroplast development and the transition from heterotrophic to phototrophic growth. Snowy cotyledon 2 (SCO2) is a DNAJ-like protein involved in thylakoid membrane biogenesis and interacts with the light-harvesting chlorophyll-binding protein LHCB1. In Arabidopsis thaliana, SCO2 function was previously reported to be restricted to cotyledons. Here we show that disruption of SCO2 in Lotus japonicus results not only in paler cotyledons but also in variegated true leaves. Furthermore, smaller and pale-green true leaves can also be observed in A. thaliana sco2 (atsco2) mutants under short-day conditions. In both species, SCO2 is required for proper accumulation of PSII-LHCII complexes. In contrast to other variegated mutants, inhibition of chloroplastic translation strongly affects L. japonicus sco2 mutant development and fails to suppress their variegated phenotype. Moreover, inactivation of the suppressor of variegation AtClpR1 in the atsco2 background results in an additive double-mutant phenotype with variegated true leaves. Taken together, our results indicate that SCO2 plays a distinct role in PSII assembly or repair and constitutes a novel factor involved in leaf variegation.
植物中含有各种因子，这些因子与类囊体多蛋白复合物的亚基或中间产物短暂相互作用，促进它们的稳定结合和整合。因此，组装因子对于叶绿体的发育和从异养到光养生长的转变是必不可少的。雪绒花状子叶 2（SCO2）是一种 DNAJ 样蛋白，参与类囊体膜的生物发生，并与光捕获叶绿素结合蛋白 LHCB1 相互作用。在拟南芥中，先前报道 SCO2 的功能仅限于子叶。在这里，我们表明，在百脉根中破坏 SCO2 不仅导致子叶变浅，而且导致真叶出现斑驳。此外，在短日照条件下，A. thaliana sco2（atsco2）突变体也可以观察到较小和浅绿色的真叶。在这两个物种中，SCO2 是 PSII-LHCII 复合物适当积累所必需的。与其他斑驳突变体不同，叶绿体翻译的抑制强烈影响百脉根 sco2 突变体的发育，并不能抑制其斑驳表型。此外，在 atsco2 背景下失活斑驳抑制因子 AtClpR1 会导致具有斑驳真叶的附加双突变体表型。总之，我们的结果表明，SCO2 在 PSII 组装或修复中发挥独特作用，是参与叶片斑驳的一个新因子。
