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RFLP analysis of mitochondrial DNA from cytoplasmic male-sterile lines of pearl millet
R Rajeshwari1, S Sivaramakrishnan, R L Smith
1School of Life Sciences, University of Hyderabad, P. O. 500 134, Gachibowli, India.
Abstract:
Mitochondrial DNA (mtDNA) from 13 cytoplasmic male-sterile (cms) lines from diverse sources were characterized by Southern blot hybridization to pearl millet and maize mtDNA probes. Hybridization patterns of mtDNA digested with PstI, BamHI, SmaI or XhoI and probed with 13.6-, 10.9-, 9.7- or 4.7-kb pearl millet mtDNA clones revealed similarities among the cms lines 5141 A and ICMA 1 (classified as the S-A1 type of cytoplasm based on fertility restoration patterns), PMC 30A and ICMA 2. The remaining cms lines formed a distinct group, within which three subgroups were evident. Among the maize mitochondiral gene clones used, the coxI probe revealed two distinct groups of cytoplasms similar to the pearl millet mtDNA clones. The atp9 probe differentiated the cms line 81 A4, derived from P. glaucum subsp. monodii, while the coxII gene probe did not detect any polymorphism among the cms lines studied. MtDNA digested with BamHI, PstI or XhoI and hybridized to the atp6 probe revealed distinct differences among the cms lines. The maize atp6 gene clone identified four distinct cytoplasmic groups and four subgroups within a main group. The mtDNA fragments hybridized to the atp6 gene probe with differing intensities, suggesting the presence of more than one copy of the gene in different stoichiometries. Rearrangements involving the coxI and/or rrn18-rrn5 genes (mapped within the pearl millet clones) probably resulted in the S-A1 type of sterility. Rearrangements involving the atp6 gene (probably resulting in chimeric form) may be responsible for male sterility in other cms lines of pearl millet.
Insights
Mitochondrial DNA (mtDNA) analysis revealed distinct cytoplasmic groups in pearl millet cytoplasmic male-sterile (cms) lines. Rearrangements in specific genes like atp6 likely cause male sterility in these important crop lines.
Area of Science:
- Plant genetics
- Molecular biology
- Agriculture
Background:
- Cytoplasmic male sterility (cms) is crucial for hybrid seed production in pearl millet.
- Understanding the genetic basis of cms is essential for breeding programs.
Purpose of the Study:
- To characterize mitochondrial DNA (mtDNA) from diverse pearl millet cms lines.
- To identify genetic variations associated with different cms types.
Main Methods:
- Southern blot hybridization using pearl millet and maize mtDNA probes.
- Digestion of mtDNA with restriction enzymes (PstI, BamHI, SmaI, XhoI).
- Hybridization with specific gene probes (coxI, atp9, coxII, atp6, rrn18-rrn5).
Main Results:
- mtDNA analysis revealed similarities and distinct groups among cms lines.
- The coxI probe identified two distinct cytoplasmic groups.
- The atp6 gene probe differentiated four distinct cytoplasmic groups and subgroups, with varying gene copy numbers.
- Rearrangements in coxI, rrn18-rrn5, or atp6 genes are implicated in male sterility.
Conclusions:
- Distinct cytoplasmic groups exist within pearl millet cms lines.
- Gene rearrangements, particularly involving atp6, are likely causes of cytoplasmic male sterility.
- This research provides insights into the molecular basis of cms in pearl millet.
