Background

The chloroplast signal recognition particle 54 (cpSRP54) is known for targeting the light-harvesting complex proteins to thylakoids and plays a critical role for chloroplast development in Arabidopsis, but little is known in rice. Here, we reported two homologous cpSRP54s that affect chloroplast development and plant survival in rice.

Results

Two rice cpSRP54 homologues, OscpSRP54a and OscpSRP54b, were identified in present study. The defective OscpSRP54a (LOC_Os11g05552) was responsible for the pale green leaf phenotype of the viable pale green leaf 14 (pgl14) mutant. A single nucleotide substitution from G to A at the position 278, the first intron splicing site, was detected in LOC_Os11g05552 in pgl14. The wild type allele could rescue the mutant phenotype. Knockout lines of OscpSRP54b (LOC_Os11g05556) exhibited similar pale green phenotype to pgl14 with reduced chlorophyll contents and impaired chloroplast development, but showed apparently arrested-growth and died within 3 weeks. Both OscpSRP54a and OscpSRP54b were constitutively expressed mainly in shoots and leaves at the vegetative growth stage. Subcellular location indicated that both OscpSRP54a and OscpSRP54b were chloroplast-localized. Both OscpSRP54a and OscpSRP54b were able to interact with OscpSRP43, respectively. The transcript level of OscpSRP43 was significantly reduced while the transcript level of OscpSRP54b was apparently increased in pgl14. In contrast, the transcript levels of OscpSRP54a, OscpSRP43 and OscpSRP54b were all significantly decreased in OscpSRP54b knockout lines.

Conclusion

Our study demonstrated that both OscpSRP54a and OscpSRP54b were essential for normal chloroplast development by interacting with OscpSRP43 in rice. OscpSRP54a and OscpSRP54b might play distinct roles in transporting different chloroplast proteins into thylakoids through cpSRP-mediated pathway.

中文翻译：

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叶绿体SRP54s是水稻叶绿体发育必不可少的。

背景

叶绿体信号识别颗粒54（cpSRP54）以将采光复合蛋白靶向类囊体而闻名，并且对于拟南芥中叶绿体的发育起着至关重要的作用，但在水稻中却鲜为人知。在这里，我们报道了两个同源的cpSRP54s，它们影响水稻的叶绿体发育和植物存活。

结果

在本研究中鉴定了两个水稻cpSRP54同源物OscpSRP54a和OscpSRP54b。有缺陷的OscpSRP54a（LOC_Os11g05552）负责活的淡绿色叶片14（pgl14）突变体的淡绿色叶片表型。从G A单核苷酸取代至A在位置278，第一个内含子剪接位点，在检测到LOC_Os11g05552在pgl14。野生型等位基因可以挽救突变表型。的敲除线OscpSRP54b（LOC_Os11g05556）显示出类似的浅绿色表型到pgl14叶绿素含量降低，叶绿体发育受损，但明显生长停滞，并在3周内死亡。无论OscpSRP54a和OscpSRP54b被组成型表达主要在营养生长阶段芽和树叶。亚细胞位置表明，OscpSRP54a和OscpSRP54b都位于叶绿体中。OscpSRP54a和OscpSRP54b都能够分别与OscpSRP43交互。的转录水平OscpSRP43而转录水平显著降低OscpSRP54b中显然增加pgl14。相反，OscpSRP54a，OscpSRP43和OscpSRP54b的转录水平OscpSRP54b基因敲除品系均显着降低。

结论

我们的研究表明，OscpSRP54a和OscpSRP54b通过与水稻中的OscpSRP43相互作用，对于正常的叶绿体发育必不可少。OscpSRP54a和OscpSRP54b在通过cpSRP介导的途径将不同叶绿体蛋白转运到类囊体中可能发挥不同的作用。