Genetic diversity and reproductive biology in ecotypes of the facultative apomict Hypericum perforatum L.

Abstract

Apomixis is a mode of asexual reproduction through seed. Progeny produced by apomixis are clonal replicas of a mother plant. The essential feature of apomixis is that embryo sacs and embryos are produced in ovules without meiotic reduction or egg cell fertilisation. Thus, apomixis fixes successful gene combinations and propagates high fitness genotypes across generations. A more profound knowledge of the mechanisms that regulate reproductive events in plants would contribute fundamentally to understanding the evolution and genetic control of apomixis. Molecular markers were used to determine levels of genetic variation within and relationship among ecotypes of the facultative apomict Hypericum perforatum L. (2n ¼ 4x ¼ 32). All ecotypes were polyclonal, being not dominated by a single genotype, and characterised by different levels of differentiation among multilocus genotypes. Flow cytometric analysis of seeds indicated that all ecotypes were facultatively apomictic, with varying degrees of apomixis and sexuality. Seeds set by haploid parthenogenesis and/or by fertilisation of aposporic egg cells were detected in most populations. The occurrence of both dihaploids and hexaploids indicates that apospory and parthenogenesis may be developmentally uncoupled and supports two distinct genetic factors controlling apospory and parthenogenesis in this species. Cyto-embryological analysis showed that meiotic and aposporic processes do initiate within the same ovule: the aposporic initial often appeared evident at the time of megaspore mother cell differentiation. Our observations suggest that the egg cell exists in an active metabolic state before pollination, and that its parthenogenetic activation leading to embryo formation may occur before fertilisation and endosperm initiation.

Transferability of barley retrotransposon primers to analyze geneticstructure in Iranian Hypericum perforatum L. populations

“…Molecular markers have been used to investigate the genetic diversity, population structure, and reproductive biology of H. perforatum (Arnholdt-Schmitt, 2000;Haluŝková and Koŝuth, 2003;Barcaccia et al, 2006;Percifield et al, 2007). However, due to the lack of a specific marker system for these plants, most of the studies used marker systems such as RAPD and ISSR.…”

“…John's wort (Hypericum perforatum L.) is a perennial herb indigenous to Europe that has been introduced in many regions due to its medicinal value. It produces pharmaceutically important metabolites with antidepressive, anticancer, and antiviral activities (Kubin et al, 2005;Barcaccia et al, 2006). In recent years, interest in H. perforatum as a natural antidepressant in phytotherapy has grown rapidly.…”

“…The result revealed the occurrence of sexual recombination in H. perforatum plants. Barcaccia et al (2006) used RAPD, ISSR, and AFLP markers to determine levels of genetic variation within and among 15 local populations of H. perforatum L. collected from northern Italy, provinces of Belluno and Treviso. Molecular analyses revealed that all the ecotypes were polyclonal, not being dominated by a single genotype, and characterized by different levels of differentiation among multilocus genotypes.…”

RFLP analysis of cpDNA in the genus Hypericum

“…Arnholdt-Schmitt (2000) investigated the mode of reproduction in H. perforatum using RAPD markers, Mayo & Langridge (2003) using multilocus genomic DNA RFLP and amplified fragment length polymorphism (AFLP). Intermicrosatellite (ISSR), RAPD or AFLP were applied to determine levels of genetic variation of natural H. perforatum populations (Barcaccia et al 2006;Hazler Pilepić et al 2008) or in comparison of natural H. perforatum populations with commercially cultivated ac-cessions (Percifield et al 2007). Variable numbers of tandem repeats (VNTR) were used to distinguished apomictically and sexually derived plants in testing of hypericin content in in vitro regenerating plants and their seed progeny (Koperdakova et al 2007).…”

Reproductive biology and cytology of Hypericum brasiliense Choisy (Hypericaceae)

“…Some researchers have related the occurrence of apomixy in H. perforatum, recognizing this species as a facultative apomictic one, due to the occurrence of sexual and aposporic processes in the same plants (Noack 1939, Matzk et al 2001, Barcaccia et al 2006. A study of reproduction pathways of H. perforatum identifi ed 11 distinct mechanisms of seed formation and observed the occurrence of pseudogamy and apospory (Matzk et al 2001).…”