A transcriptional alteration on the atp9 gene is associated with a sunflower male-sterile cytoplasm

Abstract

The transcriptional patterns of six mitochondrial genes were studied in different nuclear backgrounds for four sunflower cytoplasmic male sterility (CMS) lines. Probes coding for cob, coxI, coxII and atp6 did not detect differences between the CMS lines and male-fertile lines. atpA transcripts seemed to be dependent on the cytotype but were not related to the CMS trait in the genotypes studied. However, the atp9 probe detected transcripts of 500 and 1,100 nt in the CMS-PEF1, while the fertile forms showed a single transcript of 650 nt. Nuclear genes that restore fertility specifically rectified this alteration, suggesting that modified atp9 transcripts are associated with CMS in PEF1 sunflower. Cloning and sequencing of atp9 from CMS-PEF1 and comparison with the corresponding male-fertile gene showed the insertion of a 0.5-kbp sequence in the 3’ UTR of the gene that may be at the origin of the PEF1-CMS and the altered transcripts detected in this study.