The mitochondrial pentatricopeptide repeat protein PPR19 is involved in the stabilization of NADH dehydrogenase 1 transcripts and is crucial for mitochondrial function and Arabidopsis thaliana development

Abstract

Despite the importance of pentatricopeptide repeat (PPR) proteins in organellar RNA metabolism and plant development, the functions of many PPR proteins remain unknown. Here, we determined the role of a mitochondrial PPR protein (At1g52620) comprising 19 PPR motifs, thus named PPR19, in Arabidopsis thaliana. The ppr19 mutant displayed abnormal seed development, reduced seed yield, delayed seed germination, and retarded growth, indicating that PPR19 is indispensable for normal growth and development of Arabidopsis thaliana. Splicing pattern analysis of mitochondrial genes revealed that PPR19 specifically binds to the specific sequence in the 3'-terminus of the NADH dehydrogenase 1 (nad1) transcript and stabilizes transcripts containing the second and third exons of nad1. Loss of these transcripts in ppr19 leads to multiple secondary effects on accumulation and splicing of other nad1 transcripts, from which we can infer the order in which cis- and trans-spliced nad1 transcripts are normally processed. Improper splicing of nad1 transcripts leads to the absence of mitochondrial complex I and alteration of the nuclear transcriptome, notably influencing the alternative splicing of a variety of nuclear genes. Our results indicate that the mitochondrial PPR19 is an essential component in the splicing of nad1 transcripts, which is crucial for mitochondrial function and plant development.

Rice FLOURY ENDOSPERM10 encodes a pentatricopeptide repeat protein that is essential for the trans‐splicing of mitochondrial nad1 intron 1 and endosperm development

“…b). Thus, we suspected that defective nad1 intron 1 splicing in flo10 might result from the instability of the exon 1 precursor, a similar mechanism to that in the mtsf2 / ppr19 mutant (Lee et al ., ; Wang C. et al ., 2017). To corroborate this hypothesis, Northern blotting was performed using probes specific to nad1 exon 1 and exons 2–5 precursors.…”

“…c,d). Interestingly, the overaccumulated nad1 exon 1 precursors in flo10 were up to 3 kb in size, which is larger than the exon 1 coding region and even larger than that detected in Arabidopsis (Lee et al ., ; Wang C. et al ., 2017). A probe specific to the 5′‐portion of nad1 intron 1 (intron1a) also detected the larger exon 1 precursors, suggesting that the overaccumulated larger exon 1 precursors in flo10 may exist in the form of exon1‐intron1a (Fig.…”

“…P‐type PPR proteins AtOTP43, AtMTSF2/AtPPR19, ZmEMP11 (homolog of AtMTSF2) and ZmDEK2 were identified as trans ‐splicing factors of nad1 intron 1 in Arabidopsis and maize (de Longevialle et al ., ; Lee et al ., ; Qi et al ., ; Ren et al ., ; Wang C. et al ., 2017). Nuclear‐encoded maturase‐related proteins AtnMat1 and AtnMat4 were also implicated in trans ‐splicing of nad1 intron 1 in Arabidopsis (Keren et al ., ; Cohen et al ., ).…”

“…Most mitochondrial group II introns are resident in genes encoding subunits of complex I, the largest and most complicated enzyme in the electron transport chain (Braun et al ., ). In Arabidopsis and maize, several P‐type PPR proteins have been shown to play an essential role in intron(s) splicing of mitochondria transcripts and seed development, such as AtOTP43, AtMTSF2/AtPPR19, ZmEMP10, ZmEMP16, ZmDEK2 and ZmDEK35 (de Longevialle et al ., ; Xiu et al ., ; Cai et al ., ; Chen et al ., ; Lee et al ., ; Qi et al ., ; Wang C. et al ., ). Although relationships between these PPR proteins and their corresponding introns have been established, the underlying splicing mechanism of most of them is currently unknown.…”

The pentatricopeptide repeat protein EMPTY PERICARP8 is required for the splicing of three mitochondrial introns and seed development in maize

“…A block in splicing of the nad2 intron 1 in emp10 mutants causes a slight increase in Nad9 (Cai et al ., ). The failure in splicing of nad1 in nmat4 and ppr19 mutants does not decrease the amount of Nad9 (Cohen et al ., ; Lee et al ., ). These results strengthen the hypothesis that a likely secondary effect occurs with respect to dysfunctional complex I and re‐adjustment of relative proteins.…”