Open Access Research article

An unedited 1.1 kb mitochondrial orfB gene transcript in the Wild Abortive Cytoplasmic Male Sterility (WA-CMS) system of Oryza sativa L. subsp. indica

Srirupa Das12, Supriya Sen13, Anirban Chakraborty1, Papia Chakraborti14, Mrinal K Maiti1, Asitava Basu1, Debabrata Basu15 and Soumitra K Sen1*

Author Affiliations

1 Advanced Laboratory for Plant Genetic Engineering (formerly IIT-BREF Biotek), Indian Institute of Technology, Kharagpur- 721302, India

2 Dept of Pathology, Baylor College of Medicine, One Baylor Plaza, S209 Houston, Texas 77030, USA

3 Stein Clinical Res Bldg 201, California University, San Diego, La Jolla CA 92093-0673, USA

4 Bramhanand KC College, Kolkata- 700 035, India

5 Bose Institute, Kolkata- 700 009, India

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BMC Plant Biology 2010, 10:39  doi:10.1186/1471-2229-10-39

Published: 2 March 2010

Abstract

Background

The application of hybrid rice technology has significantly increased global rice production during the last three decades. Approximately 90% of the commercially cultivated rice hybrids have been derived through three-line breeding involving the use of WA-CMS lines. It is believed that during the 21st century, hybrid rice technology will make significant contributions to ensure global food security. This study examined the poorly understood molecular basis of the WA-CMS system in rice.

Results

RFLPs were detected for atp6 and orfB genes in sterile and fertile rice lines, with one copy of each in the mt-genome. The RNA profile was identical in both lines for atp6, but an additional longer orfB transcript was identified in sterile lines. 5' RACE analysis of the long orfB transcript revealed it was 370 bp longer than the normal transcript, with no indication it was chimeric when compared to the genomic DNA sequence. cDNA clones of the longer orfB transcript in sterile lines were sequenced and the transcript was determined unedited. Sterile lines were crossed with the restorer and maintainer lines, and fertile and sterile F1 hybrids were respectively generated. Both hybrids contained two types of orfB transcripts. However, the long transcript underwent editing in the fertile F1 hybrids and remained unedited in the sterile lines. Additionally, the editing of the 1.1 kb orfB transcript co-segregated with fertility restoring alleles in a segregating population of F2 progeny; and the presence of unedited long orfB transcripts was detected in the sterile plants from the F2 segregating population.

Conclusion

This study helped to assign plausible operative factors responsible for male-sterility in the WA cytoplasm of rice. A new point of departure to dissect the mechanisms governing the CMS-WA system in rice has been identified, which can be applied to further harness the opportunities afforded by hybrid vigor in rice.