| Plastids and mitochondria, in a standard genetic cross, are transmitted to the seed progeny by the maternal parent in Arabidopsis thaliana. My objective was to test, if exceptional pollen transmission of plastid occurs in Arabidopsis, a species in which no plastid DNA could be detected in pollen or sperm cells by cytological methods. The maternal parent was the nuclear male sterile (ms1-1/ms1-1), spectinomycin sensitive Ler ecotype and the pollen parent was the male fertile RLD-Spc1 plant carrying a plastid-encoded spectinomycin resistance mutation. I selected for exceptional pollen transmission in the progeny by spectinomycin resistance encoded in the paternal plastid DNA. I found that plastids, in general, are inherited maternally in Arabidopsis and rare events of paternal plastid transmission to the seed progeny occurs at a low (3.9 × 10-5) frequency. This observation extends previous reports in Nicotiana tabacum (family: Solanaceae) to a cruciferous species suggesting that low frequency paternal leakage of plastids via pollen may be universal in plants previously thought to exhibit strict maternal plastid inheritance.;Two components needed to accomplish this study were a plastid-encoded, spectinomycin resistant mutant as the pollen parent and plastid markers to identify the origin of the plastids in the hybrid seed progeny obtained from the crosses. To identify genetic markers in the Arabidopsis thaliana plastid genome (ptDNA) I amplified and sequenced the rpl2-psbA and rbcL-accD regions in 26 ecotypes. The two regions contained eight polymorphic sites including five insertions and/or deletions (indels) involving changes in the length of A or T mononucleotide repeats and three base substitutions. The 27 alleles provided a practical set of ptDNA markers for the commonly used RLD, Ler, Col and C24 ecotypes. I used a RLD-Spc1 line carrying a plastid-encoded spectinomycin resistant mutation as the pollen parent that was compatible with the Ler maternal parent. |
