Most pentatricopeptide repeat (PPR) proteins localize to plastids or mitochondria, where they participate in RNA metabolism and post-transcriptionally regulate organelle gene expression. However, whether PPR proteins regulate the expression of nucleus-encoded genes remains unclear. Here, we uncovered a function for the rice (Oryza. sativa L.) PPR protein OsPPR2-1 (Os02g0110400) in pollen development and showed that, in contrast to most other PPR proteins, OPPR2-1 resides in the cytoplasm. Downregulating OsPPR2-1 expression led to abnormal plastid development in tapetal cells, prolonged programmed cell death (PCD), prolonged tapetum degradation, and significantly reduced pollen fertility. Transcriptome analysis revealed that the expression of OsGOLDEN-LIKE 1 (OsGLK1), encoding a transcription factor that regulates plastid development and maintenance, was significantly higher in plants with downregulated OsPPR2-1 expression compared to the wild type. Moreover, OsPPR2-1 bound to the OsGLK1 mRNA in RNA immunoprecipitation and RNA-electrophoretic mobility shift assays. An in vitro cleavage assay showed that OsPPR2-1 could degrade the OsGLK1 mRNA. Notably, knockdown of OsGLK1 partially restored pollen fertility in OsPPR2-1-knockdown plants and OsGLK1-overexpressing plants showed abnormal tapetum and plastid development, similar to the OsPPR2-1-knockdown plants. Together, our findings demonstrate that OsPPR2-1 regulates OsGLK1 expression, thereby controlling plastid development and PCD in the tapetum.

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The full text of this article is available to read as a PDF.
There is NO Competing Interest.
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Posted 29 Jan, 2021
Posted 29 Jan, 2021
Most pentatricopeptide repeat (PPR) proteins localize to plastids or mitochondria, where they participate in RNA metabolism and post-transcriptionally regulate organelle gene expression. However, whether PPR proteins regulate the expression of nucleus-encoded genes remains unclear. Here, we uncovered a function for the rice (Oryza. sativa L.) PPR protein OsPPR2-1 (Os02g0110400) in pollen development and showed that, in contrast to most other PPR proteins, OPPR2-1 resides in the cytoplasm. Downregulating OsPPR2-1 expression led to abnormal plastid development in tapetal cells, prolonged programmed cell death (PCD), prolonged tapetum degradation, and significantly reduced pollen fertility. Transcriptome analysis revealed that the expression of OsGOLDEN-LIKE 1 (OsGLK1), encoding a transcription factor that regulates plastid development and maintenance, was significantly higher in plants with downregulated OsPPR2-1 expression compared to the wild type. Moreover, OsPPR2-1 bound to the OsGLK1 mRNA in RNA immunoprecipitation and RNA-electrophoretic mobility shift assays. An in vitro cleavage assay showed that OsPPR2-1 could degrade the OsGLK1 mRNA. Notably, knockdown of OsGLK1 partially restored pollen fertility in OsPPR2-1-knockdown plants and OsGLK1-overexpressing plants showed abnormal tapetum and plastid development, similar to the OsPPR2-1-knockdown plants. Together, our findings demonstrate that OsPPR2-1 regulates OsGLK1 expression, thereby controlling plastid development and PCD in the tapetum.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7
The full text of this article is available to read as a PDF.
There is NO Competing Interest.
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