AUTHOR=Yang Huanhuan , Xiu Zhihui , Wang Le , Cao Shi-Kai , Li Xiulan , Sun Feng , Tan Bao-Cai 

TITLE=Two Pentatricopeptide Repeat Proteins Are Required for the Splicing of nad5 Introns in Maize

JOURNAL=Frontiers in Plant Science

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2020.00732

DOI=10.3389/fpls.2020.00732

ISSN=1664-462X

ABSTRACT=<p>Mitochondrial genes in flowering plants contain predominantly group II introns that require precise splicing before translation into functional proteins. Splicing of these introns is facilitated by various nucleus-encoded splicing factors. Due to lethality of mutants, functions of many splicing factors have not been revealed. Here, we report the function of two P-type PPR proteins PPR101 and PPR231, and their role in maize seed development. PPR101 and PPR231 are targeted to mitochondria. Null mutation of <italic>PPR101</italic> and <italic>PPR231</italic> arrests embryo and endosperm development, generating <italic>empty pericarp</italic> and <italic>small kernel</italic> phenotype, respectively, in maize. Loss-of-function in PPR101 abolishes the splicing of <italic>nad5</italic> intron 2, and reduces the splicing of <italic>nad5</italic> intron 1. Loss-of-function in PPR231 reduces the splicing of <italic>nad5</italic> introns 1, 2, 3 and <italic>nad2</italic> intron 3. The absence of Nad5 protein eliminates assembly of complex I, and activates the expression of alternative oxidase AOX2. These results indicate that both PPR101 and PPR231 are required for mitochondrial <italic>nad5</italic> introns 1 and 2 splicing, while PPR231 is also required for <italic>nad5</italic> intron 3 and <italic>nad2</italic> intron 3. Both genes are essential to complex I assembly, mitochondrial function, and maize seed development. This work reveals that the splicing of a single intron involves multiple PPRs.</p>