Cloning and Expression Analysis of Eight Upland Cotton Pentatricopeptide Repeat Family Genes

The pentatricopeptide repeat (PPR) gene family is one of the largest gene families in plants. Most PPR genes are localized in mitochondria and chloroplasts functioning in regulation of plant growth and development, fertility restoration for cytoplasmic male sterility (CMS), and stress defense. In this study, using in silico cloning and PCR amplification with degenerate primers based on Arabidopsis PPR genes, we cloned eight new full-length PPR genes encoding protein sequences ranging from 458 to 875 amino acids, with 8 to 16 repetitive PPR elements in upland cotton and all of them lack introns. Expression analysis revealed that eight PPR genes were differently expressed in roots, stems, leaves, and floral buds. As for GhI12, its expression in floral buds at days 3-5 was significantly higher in line 777R (restorer line) than in line 777A (CMS line). Further tests with real-time PCR showed that GhI12 expression peaked at day 3 in 777R, followed by a gradual decline, while its expression fluctuated in 777A, peaking at day 5 and day 13. In addition, Gh155c17 and GhI12 were upregulated under salt stress. This is the first report of upland cotton PPR genes involved in salt stress response.