Abstract
Plastid inheritance in angiosperms is presumed to be largely maternal, with the potential to inherit plastids biparentally estimated for about 20% of species. In Passiflora, maternal, paternal and biparental inheritance has been reported; however, these studies were limited in the number of crosses and progeny examined. To improve the understanding of plastid transmission in Passiflora, the progeny of 45 interspecific crosses were analyzed in the three subgenera: Passiflora, Decaloba and Astrophea. Plastid types were assessed following restriction digestion of PCR amplified plastid DNA in hybrid embryos, cotyledons and leaves at different developmental stages. Clade-specific patterns of inheritance were detected such that hybrid progeny from subgenera Passiflora and Astrophea predominantly inherited paternal plastids with occasional incidences of maternal inheritance, whereas subgenus Decaloba showed predominantly maternal and biparental inheritance. Biparental plastid inheritance was also detected in some hybrids from subgenus Passiflora. Heteroplasmy due to biparental inheritance was restricted to hybrid cotyledons and first leaves with a single parental plastid type detectable in mature plants. This indicates that in Passiflora, plastid retention at later stages of plant development may not reflect the plastid inheritance patterns in embryos. Passiflora exhibits diverse patterns of plastid inheritance, providing an excellent system to investigate underlying mechanisms in angiosperms.
Highlights
Plant cells house three genome-containing organelles: the nucleus, the mitochondrion and the plastid
This may explain the instances of biparental inheritance and paternal/maternal leakage detected in Passiflora, but is not adequate to explain predominant paternal inheritance in subgenus
A conflicting relationship was identified in Passiflora phylogenetic studies using heteroplasmic plastome loci, suggesting that researchers should be cautious in interpreting phylogenetic relationships in the genus with plastid data [41]
Summary
Plant cells house three genome-containing organelles: the nucleus, the mitochondrion and the plastid. The stochastic process of partitioning during plastid and cell division usually results in plastome homogeneity (homoplasmy) early in plant development [1,2,3,4]. Taken together, these genetic features suggest plastomes are generally homogenous despite the presence of many unit genomes per nucleoid, nucleoids per plastid and plastids per cell [5]. Cytological screenings of pollen for plastid DNA (ptDNA) of nearly angiosperm species reported that approximately 80% and 20% have the potential for maternal and biparental plastid transmission, respectively [7,8]. The bias toward maternal inheritance is attributed to the distribution of plastids during pollen development
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