ORGANELLE INHERITANCE IN PLANTS

Most angiosperms are thought to share strict maternal inheritance of b oth plastids and mitochondria. Exceptions have been described and anal ysed, especially for plastids. However, the lack of phenotypic markers and the use of RFLPs on small samples may have biased the prevailing view of organelle inheritance by underestimating the occurrence of low -frequency paternal transmission of organelles. According to Muller's Ratchet, some recombination among organelle genomes is required, which would necessitate at least occasional biparental transmission. Unipar ental inheritance can reduce the spread of selfish genetic elements an d maintain good combinations of alleles. However, this does not explai n why organelles transmitted by both parents have not invaded populati ons with uniparental inheritance. A link between outcrossing reproduct ive systems and the occurrence of biparental transmission suggests tha t plastids may play more of a genetic role in their inheritance than i s usually assumed. Their prevailing non-Mendelian mode of inheritance thus remains to be convincingly explained.