Selective egg cell polyspermy bypasses the triploid block.

Yanbo Mao,Dieu Vo,Thomas Nakel,Ivo Grosse,Alexander Gabel,Rita Groß-Hardt,Dawit Girma Tekleyohans,Thomas Baum,Prisca Viehöver

doi:10.7554/elife.52976

Yanbo Mao, Dieu Vo + Show 7 more

Open Access

https://doi.org/10.7554/elife.52976

Copy DOI

Abstract

Polyploidization, the increase in genome copies, is considered a major driving force for speciation. We have recently provided the first direct in planta evidence for polyspermy induced polyploidization. Capitalizing on a novel sco1-based polyspermy assay, we here show that polyspermy can selectively polyploidize the egg cell, while rendering the genome size of the ploidy-sensitive central cell unaffected. This unprecedented result indicates that polyspermy can bypass the triploid block, which is an established postzygotic polyploidization barrier. In fact, we here show that most polyspermy-derived seeds are insensitive to the triploid block suppressor admetos. The robustness of polyspermy-derived plants is evidenced by the first transcript profiling of triparental plants and our observation that these idiosyncratic organisms segregate tetraploid offspring within a single generation. Polyspermy-derived triparental plants are thus comparable to triploids recovered from interploidy crosses. Our results expand current polyploidization concepts and have important implications for plant breeding.

Highlights

The evolutionary history of flowering plants is characterized by recurrent polyploidization events (Comai, 2005; De Bodt et al, 2005; Otto and Whitton, 2000; Van de Peer et al, 2017)
The generation of triploid plants via unreduced male gametes is limited by the triploid block, which is a postzygotic hybridization barrier operating in many plants species (Dilkes et al, 2008; Kohler et al, 2010; Marks, 1966; Ramsey and Schemske, 1998; Scott et al, 1998)
TT3 plants initiate flowering only after 64.6 ± 5.4 days, which is around 20, 17 and 15 days after the respective parental lines have terminated their flowering phase (Figure 4E; Figure 4—figure supplement 4B). Even though these data are obtained under optimized growth condition, the results suggest that polyspermy-derived triploid three accession hybrids are reproductively isolated from the parental plants in the first generation

Summary

Introduction

The evolutionary history of flowering plants is characterized by recurrent polyploidization events (Comai, 2005; De Bodt et al, 2005; Otto and Whitton, 2000; Van de Peer et al, 2017). Recent in planta and in vitro assays have provided the first direct evidence that viable polyploid plants can arise from polyspermy, the fusion of one egg cell with supernumerary sperm (Nakel et al, 2017; Toda et al, 2016). This previous work indicates that a single Arabidopsis plant can generate several polyspermy-induced triploid seedlings (Nakel et al, 2017). The triploid block is explained by the unique reproductive mode of flowering plants, which involves fertilization of two female gametes, the egg

Objectives

Methods

Results

Conclusion