Dek504 Encodes a Mitochondrion-Targeted E+-Type Pentatricopeptide Repeat Protein Essential for RNA Editing and Seed Development in Maize

A Systemic Investigation of Genetic Architecture and Gene Resources Controlling Kernel Size-Related Traits in Maize

Grain yield is the most critical and complex quantitative trait in maize. Kernel length (KL), kernel width (KW), kernel thickness (KT) and hundred-kernel weight (HKW) associated with kernel size are essential components of yield-related traits in maize. With the extensive use of quantitative trait locus (QTL) mapping and genome-wide association study (GWAS) analyses, thousands of QTLs and quantitative trait nucleotides (QTNs) have been discovered for controlling these traits. However, only some of them have been cloned and successfully utilized in breeding programs. In this study, we exhaustively collected reported genes, QTLs and QTNs associated with the four traits, performed cluster identification of QTLs and QTNs, then combined QTL and QTN clusters to detect consensus hotspot regions. In total, 31 hotspots were identified for kernel size-related traits. Their candidate genes were predicted to be related to well-known pathways regulating the kernel developmental process. The identified hotspots can be further explored for fine mapping and candidate gene validation. Finally, we provided a strategy for high yield and quality maize. This study will not only facilitate causal genes cloning, but also guide the breeding practice for maize.

Maize PPR-E proteins mediate RNA C-to-U editing in mitochondria by recruiting the trans deaminase PCW1

RNA C-to-U editing in organelles is essential for plant growth and development; however, the underlying mechanism is not fully understood. Here, we report that pentatricopeptide repeat (PPR)-E subclass proteins carry out RNA C-to-U editing by recruiting the trans deaminase PPR motifs, coiled-coil, and DYW domain-containing protein 1 (PCW1) in maize (Zea mays) mitochondria. Loss-of-function of bZIP and coiled-coil domain-containing PPR 1 (bCCP1) or PCW1 arrests seed development in maize. bCCP1 encodes a bZIP and coiled-coil domain-containing PPR protein, and PCW1 encodes an atypical PPR-DYW protein. bCCP1 is required for editing at 66 sites in mitochondria and PCW1 is required for editing at 102 sites, including the 66 sites that require bCCP1. The PCW1-mediated editing sites are exclusively associated with PPR-E proteins. bCCP1 interacts with PCW1 and the PPR-E protein Empty pericarp7 (EMP7). Two multiple organellar RNA editing factor (MORF) proteins, ZmMORF1 and ZmMORF8, interact with PCW1, EMP7, and bCCP1. ZmMORF8 enhanced the EMP7-PCW1 interaction in a yeast three-hybrid assay. C-to-U editing at the ccmFN-1553 site in maize required EMP7, bCCP1, and PCW1. These results suggest that PPR-E proteins function in RNA editing by recruiting the trans deaminase PCW1 and bCCP1, and MORF1/8 assist this recruitment through protein-protein interactions.

Exploring the RNA Editing Events and Their Potential Regulatory Roles in Tea Plant (Camellia sinensis L.)

RNA editing is a post-transcriptional modification process that alters the RNA sequence relative to the genomic blueprint. In plant organelles (namely, mitochondria and chloroplasts), the most common type is C-to-U, and the absence of C-to-U RNA editing results in abnormal plant development, such as etiolation and albino leaves, aborted embryonic development and retarded seedling growth. Here, through PREP, RES-Scanner, PCR and RT-PCR analyses, 38 and 139 RNA editing sites were identified from the chloroplast and mitochondrial genomes of Camellia sinensis, respectively. Analysis of the base preference around the RNA editing sites showed that in the -1 position of the edited C had more frequent occurrences of T whereas rare occurrences of G. Three conserved motifs were identified at 25 bases upstream of the RNA editing site. Structural analyses indicated that the RNA secondary structure of 32 genes, protein secondary structure of 37 genes and the three-dimensional structure of 5 proteins were altered due to RNA editing. The editing level analysis of matK and ndhD in six tea cultivars indicated that matK-701 might be involved in the color change of tea leaves. Furthermore, 218 PLS-CsPPR proteins were predicted to interact with the identified RNA editing sites. In conclusion, this study provides comprehensive insight into RNA editing events, which will facilitate further study of the RNA editing phenomenon of the tea plant.