Reconstruction of reproductive diversity in Hypericum perforatum L. opens novel strategies to manage apomixis

Abstract

SummaryThe mode of reproduction was characterized for 113 accessions of the tetraploid facultative apomictic species Hypericum perforatum using bulked or single mature seeds in the¯ow cytometric seed screen (FCSS). This screen discriminates several processes of sexual or asexual reproduction based on DNA contents of embryo and endosperm nuclei. Seed formation in H. perforatum proved to be highly polymorphic. Eleven different routes of reproduction were determined. For the ®rst time, individual seeds were identi®ed that originated from two embryo sacs: the endosperm from an aposporous and the embryo from the legitimate meiotic embryo sac. Moreover, diploid plants were discovered, which apparently reproduce by a hitherto unknown route of seed formation, that is chromosome doubling within aposporous initial cells followed by double fertilization. Although most plants were tetraploid and facultative sexual/apomictic, diploid obligate sexuals and tetraploid obligate apomicts could be selected. Additionally, genotypes were detected which at a high frequency produced embryos either from reduced parthenogenetic or unreduced fertilized egg cells. The endosperm developed most frequently after fertilization of the central cell in aposporous embryo sacs (pseudogamy) but in few cases also autonomously. The genetic control of apomixis appears to be complex in H. perforatum. Basic material was developed for breeding H. perforatum, and strategies are suggested for elucidation of inheritance as well as evolution of apomixis and for molecular approaches of apomixis engineering.

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

“…FCSSs were performed according to the procedure described by Matzk et al (2001). Bulks of 30 mature seeds each were used for the estimation of embryo and residual endosperm nuclear DNA contents of the 15 local populations and the cultivar Topas.…”

“…Apomixis in this species is achieved through apomeiosis of the aposporic Hieracium-type, followed by parthenogenesis of the unreduced egg cell. Fertilisation of the central cell of aposporic embryo sacs by a pollen nucleus is normally required for endosperm formation (pseudogamy), although the endosperm rarely can also develop autonomously (Matzk et al, 2001). H. perforatum is a facultative apomict since sexual and aposporic processes can occur in the same plant.…”

“…Apomixis in H. perforatum was first described in the pioneering work of Noack (1939), but only recently characterised in great detail by Matzk et al (2001) using the flow cytometric seed screen (FCSS). This latter study identified 11 different mechanisms of seed formation, in addition to low numbers of obligate sexually and apomictically reproducing plants: embryos of sexual origin were mainly diploid (2n ¼ 2x ¼ 16), while apomictically formed embryos were tetraploid (2n ¼ 4x ¼ 32) or hexaploid (2n ¼ 6x ¼ 48).…”

“…The aim of this work was to gain an insight into the reproductive dynamics and the developmental events of apomixis in H. perforatum, a species recently considered as a favourable model for apomixis research (Matzk et al, 2001(Matzk et al, , 2003. A survey of the genetic variation and differentiation occurring within and among natural populations was carried out using multilocus PCR-based molecular markers.…”

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). An analysis of 55 species of the genus Hypericum demonstrated a high plasticity of reproduction pathways (Matzk et al 2003).…”