Exceptional transmission of plastids and mitochondria from the transplastomic pollen parent and its impact on transgene containment

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 104; no. 17; pp. 7003 - 7008
• Main Authors: Svab, Zora, Maliga, Pal
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 24.04.2007; National Acad Sciences
• Series: From the Cover
• Subjects: aadA gene; Biological Sciences; Botany; chloroplast DNA; Containment of Biohazards; Crosses, Genetic; Cytoplasm - genetics; cytoplasmic inheritance; cytoplasmic male sterility; DNA Probes; DNA, Chloroplast - genetics; DNA, Mitochondrial - genetics; Drug Resistance; genome; Genomics; Grain; Heredity; Inheritance Patterns - genetics; Mitochondria - genetics; Nicotiana - genetics; Nicotiana tabacum; Nicotiana undulata; paternal mitochondrial DNA; paternal plastid DNA; Plant Infertility; Plant reproduction; plastid DNA; Plastids - genetics; Pollen; Pollen - genetics; pollination; Polymorphism, Restriction Fragment Length; Selection, Genetic; Tobacco; transgene contamination; Transgenes; Transgenic plants
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0700063104

Plastids in Nicotiana tabacum are normally transmitted to the progeny by the maternal parent only. However, low-frequency paternal plastid transmission has been reported in crosses involving parents with an alien cytoplasm. Our objective was to determine whether paternal plastids are transmitted in crosses between parents with the normal cytoplasm. The transplastomic father lines carried a spectinomycin resistance (aadA) transgene incorporated in the plastid genome. The mother lines in the crosses were either (i) alloplasmic, with the Nicotiana undulata cytoplasm that confers cytoplasmic male sterility (CMS92) or (ii) normal, with the fertile N. tabacum cytoplasm. Here we report that plastids from the transplastomic father were transmitted in both cases at low (10⁻⁴-10⁻⁵) frequencies; therefore, rare paternal pollen transmission is not simply due to breakdown of normal controls caused by the alien cytoplasm. Furthermore, we have found that the entire plastid genome was transmitted by pollen rather than small plastid genome (ptDNA) fragments. Interestingly, the plants, which inherited paternal plastids, also carried paternal mitochondrial DNA, indicating cotransmission of plastids and mitochondria in the same pollen. The detection of rare paternal plastid transmission described here was facilitated by direct selection for the transplastomic spectinomycin resistance marker in tissue culture; therefore, recovery of rare paternal plastids in the germline is less likely to occur under field conditions.