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Summary: Thioredoxins (TRXs) occur in plant chloroplasts as complex disulphide oxidoreductases. Although many biological processes are regulated by thioredoxins, the regulatory mechanism of chloroplast TRXs are largely unknown.Here we report a rice white panicle2 mutant caused by a mutation in the thioredoxin z gene, an orthologue of AtTRX z in Arabidopsis. white panicle2 (wp2) seedlings exhibited a high‐temperature‐sensitive albinic phenotype.We found that plastid multiple organellar RNA editing factors (MORFs) were the regulatory targets of thioredoxin z. We showed that OsTRX z protein physically interacts with OsMORFs in a redox‐dependent manner and that the redox state of a conserved cysteine in the MORF box is essential for MORF–MORF interactions. wp2 and OsTRX z knockout lines show reduced editing efficiencies in many plastidial‐encoded genes especially under high‐temperature conditions. An Arabidopsis trx z mutant also exhibited significantly reduced chloroplast RNA editing.Our combined results suggest that thioredoxin z regulates chloroplast RNA editing in plants by controlling the redox state of MORFs. [ABSTRACT FROM AUTHOR]

Summary: Endosperm, the major storage organ in cereal grains, determines grain yield and quality. Despite the fact that a role for P‐type pentatricopeptide repeat (PPR) proteins in the regulation of endosperm development has emerged, molecular functions of many P‐type PPR proteins remain obscure.Here, we report a rice endosperm defective mutant, floury endosperm10 (flo10), which developed smaller starch grains in starchy endosperm and abnormal cells in the aleurone layer. Map‐based cloning and rescued experiments showed that FLO10 encodes a P‐type PPR protein with 26 PPR motifs, which is localized to mitochondria. Loss of function of FLO10 affected the trans‐splicing of the mitochondrial nad1 intron 1, which was accompanied by the increased accumulation of the nad1 exon 1 and exons 2–5 precursors.The failed formation of mature nad1 led to a dramatically decreased assembly and activity of complex I, reduced ATP production, and changed mitochondrial morphology. In addition, loss of function of FLO10 significantly induced an alternative respiratory pathway involving alternative oxidase.These results reveal that FLO10 plays an important role in the maintenance of mitochondrial function and endosperm development through its effect on the trans‐splicing of the mitochondrial nad1 intron 1 in rice. [ABSTRACT FROM AUTHOR]