Submitted to: Plant Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/26/1996
Publication Date: N/A
Citation: Interpretive Summary: Essentially all grain sorghum grown in the U.S. is hybrid, and is dependent on cytoplasmic male sterility (cms) for seed production. Nearly all sorghum uses one source of cms, which results in potential genetic vulnerability to pests. We have pursued the isolation of genes causing cms in sorghum, to the end of understanding how cms works and thus allowing design and manipulation for genetic engineering of the trait. We have isolated a strong candidate gene for causality of cms in the sorghum line IS1112C. The predicted gene product is very similar to that of a rice gene also suspected to cause cms, which is unprecedented in higher plants to date. We have established that at least 14 male-sterile sorghum lines could make the protein product of the gene, but that any hybrid sorghum line for production probably cannot. We conclude that the probable gene product may cause cms. If it can be demonstrated that the gene indeed causes cms, the gene can be manipulated for introduction into agronomically important sorghum lines.
Technical Abstract: A mitochondrial DNA (mtDNA) configuration of the cytoplasmic male-sterile (cms) sorghum line IS1112C includes a 321 bp open reading frame designated orf107, encoding a polypeptide product of 11.85 kD. The open reading frame, similar to several other genes associated with cms, consists of amino terminal sequences derived from an obligate gene. Unlike other examples to date, however, the carboxy-terminal sequences are highly similar to the carboxy terminus of an open reading frame associated with cms in rice, orf79. Sorghum lines partially or fully restored to fertility exhibit a high efficiency internal-orf107 transcript processing activity, precluding abundant whole length transcripts available for translation. Male-sterile lines exhibit only a trace of the activity. Examinations of backcross and F2 lines suggest a gametophytic mode of restoration, and indicate that enhanced transcript processing activity is necessary, but not sufficient, to restore full fertility. These novel observations indicate that mitochondrial open reading frames associated with cms in different species can include highly similar motifs, and that fertility restoration could involve a mechanism by which synthesis of a cms-associated gene product may be precluded through transcript cleavage.