Abstract
Polyploidy has had a considerable impact on the evolution of many eukaryotes, especially angiosperms. Indeed, most—if not all—angiosperms have experienced at least one round of polyploidy during the course of their evolution, and many important crop plants are current polyploids. The occurrence of 2n gametes (diplogametes) in diploid populations is widely recognised as the major source of polyploid formation. However, limited information is available on the genetic control of diplogamete production. Here, we describe the isolation and characterisation of the first gene, AtPS1 (Arabidopsis thaliana Parallel Spindle 1), implicated in the formation of a high frequency of diplogametes in plants. Atps1 mutants produce diploid male spores, diploid pollen grains, and spontaneous triploid plants in the next generation. Female meiosis is not affected in the mutant. We demonstrated that abnormal spindle orientation at male meiosis II leads to diplogamete formation. Most of the parent's heterozygosity is therefore conserved in the Atps1 diploid gametes, which is a key issue for plant breeding. The AtPS1 protein is conserved throughout the plant kingdom and carries domains suggestive of a regulatory function. The isolation of a gene involved in diplogamete production opens the way for new strategies in plant breeding programmes and progress in evolutionary studies.
Highlights
Polyploidy, the condition of organisms having more than two sets of chromosomes, has had a considerable impact on the evolution of many fungi, invertebrate, and vertebrate lineages and is prominent in plants [1,2]
The realisation that gametes with somatic chromosome numbers (2n gametes or diplogametes) widely occur in diploid populations as a result of meiotic failure, led to a change of paradigm[11]; it is believed that 2n gametes are the major route for polyploidy formation, in particular by leading to the formation of triploids, which may serve as a bridge/step towards even ploidy levels [2,12,13,14,15]. 2n gametes are instrumental in the genetic improvement of several polyploid crops, where useful genes from diploid relatives are incorporated into cultivated genotypes [16,17]
We first chose a subset of known meiotic genes (AtMER3 [26], AtDMC1 [27], SDS [28], AtMND1 [29,30], AtHOP2 [31], AtMSH5 [32] and AtSPO11-1 [33]) for which the expression data appeared to be relevant: when one of these genes was used as the query in the Expression Angler tool, other known meiotic genes appeared among the first hits
Summary
Polyploidy, the condition of organisms having more than two sets of chromosomes, has had a considerable impact on the evolution of many fungi, invertebrate, and vertebrate lineages and is prominent in plants [1,2]. Even plants with small genomes, such as Arabidopsis thaliana, have been affected by polyploidy [8,9]. The realisation that gametes with somatic chromosome numbers (2n gametes or diplogametes) widely occur in diploid populations as a result of meiotic failure, led to a change of paradigm[11]; it is believed that 2n gametes are the major route for polyploidy formation, in particular by leading to the formation of triploids, which may serve as a bridge/step towards even ploidy levels [2,12,13,14,15]. The realisation that gametes with somatic chromosome numbers (2n gametes or diplogametes) widely occur in diploid populations as a result of meiotic failure, led to a change of paradigm[11]; it is believed that 2n gametes are the major route for polyploidy formation, in particular by leading to the formation of triploids, which may serve as a bridge/step towards even ploidy levels [2,12,13,14,15]. 2n gametes are instrumental in the genetic improvement of several polyploid crops, where useful genes from diploid relatives are incorporated into cultivated genotypes [16,17]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
