GmPGL2, Encoding a Pentatricopeptide Repeat Protein, Is Essential for Chloroplast RNA Editing and Biogenesis in Soybean.

Xingxing Feng,Suxin Yang,Kuanqiang Tang,Hui Yu,Cheng Zhiyuan,Jiantian Leng,Qingyu Wang,Guang Li,Yaohua Zhang

doi:10.3389/fpls.2021.690973

Abstract

Chloroplast biogenesis and development are highly complex processes requiring interactions between plastids and nuclear genomic products. Pentatricopeptide repeat (PPR) proteins play an essential role in the development of chloroplasts; however, it remains unclear how RNA editing factors influence soybean development. In this study, a Glycine max pale green leaf 2 mutant (Gmpgl2) was identified with decreased chlorophyll contents. Genetic mapping revealed that a single-nucleotide deletion at position 1949 bp in the Glyma.05g132700 gene in the Gmpgl2 mutant, resulting in a truncated GmPGL2 protein. The nuclear-encoded GmPGL2 is a PLS-type PPR protein that localizes to the chloroplasts. The C-to-U editing efficiencies of rps16, rps18, ndhB, ndhD, ndhE, and ndhF were reduced in the Gmpgl2 mutant. RNA electrophoresis mobility shift assay (REMSA) analysis further revealed that GmPGL2 binds to the immediate upstream sequences at RNA editing sites of rps16 and ndhB in vitro, respectively. In addition, GmPGL2 was found to interact with GmMORF8, GmMORF9, and GmORRM6. These results suggest that GmPGL2 participates in C-to-U RNA editing via the formation of a complex RNA editosome in soybean chloroplasts.

Highlights

The chloroplast is a vital photosynthetic organelle for plant growth and development
These results showed that the mutation in GmPGL2 leads to defects in chloroplast biogenesis
High luciferase activity was detected after the co-expression of GmMORF8, GmMORF9, and GmORRM6 fused to C-terminal luciferase (CLUC) and GmPGL2 fused to N-terminal luciferase (NLUC; Figure 6C). These findings indicated that GmPGL2 might affect RNA editing by interacting with GmMORF8, GmMORF9, and GmORRM6

Summary

Introduction

The chloroplast is a vital photosynthetic organelle for plant growth and development. It is a semi-autonomous organelle with its own DNA genome. The chloroplast proteome contains approximately 3,000 proteins, and only approximately 160 proteins are encoded by the chloroplast genome while the remainder are imported (Martin et al, 2002). The proteins encoded by the chloroplast genome include components of the chloroplast ribosome and NADH dehydrogenaselike complex, which influence plastid protein synthesis and photosystem I cyclic electron transport, respectively (Laughlin et al, 2019). RNA editing plays an important role in the biogenesis and functioning of the mitochondria and chloroplasts. The conversion of cytidines (Cs) to uridines (Us), via a deamination reaction, representing the main RNA editing mechanism in plants (Stern et al, 2004). RNA editing converts hundreds of Cs to Us at specific positions in the plastid and mitochondrial transcripts; editing often creates start or stop

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Conclusion