Haploid plants produced by centromere-mediated genome elimination

• Published in: Nature (London) Vol. 464; no. 7288; pp. 615 - 618
• Main Authors: Ravi, Maruthachalam, Chan, Simon W. L.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 25.03.2010; Nature Publishing Group
• Subjects: 631/1647/334/2244/710; 631/449/2491; 631/449/448/1358; 631/80/103/90; Agronomy. Soil science and plant productions; Arabidopsis - genetics; Arabidopsis - metabolism; Arabidopsis thaliana; Biological and medical sciences; Cell Nucleus - genetics; Centromere - metabolism; Centromeres; Chromosomes; Crosses, Genetic; Deoxyribonucleic acid; Diploidy; DNA; Embryos; Fundamental and applied biological sciences. Psychology; Generalities. Genetics. Plant material; Genetic aspects; Genetic resources, diversity; Genetics; Genetics and breeding of economic plants; Genome, Plant - genetics; Genotypes; Haploidy; Histones - genetics; Histones - metabolism; Humanities and Social Sciences; Inbreeding; Interspecific and intergeneric hybridization, introgressions; letter; Methods; multidisciplinary; Physiological aspects; Plant breeding; Plant breeding: fundamental aspects and methodology; Plant material; Plant species; Proteins; Science; Science (multidisciplinary); Structure; United States; Cell culture; Parent; Eukaryote; Chromosome; Homozygosity; Wild type; Protein; Heterozygosity; Arabidopsis thaliana; Haploidy; Diploidy; Centromere; Cruciferae; Dicotyledones; Gametophyte; Angiospermae; Inbreeding; Spermatophyta; Inheritance(genetics); Experimental plant; Genome
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature08842

When plants go halves: haploids made easy Haploid plants, inheriting chromosomes from one parent only, have important advantages in genetic research but also crucially in plant breeding, where they are used to create instant homozygous diploid lines, circumventing many generations of inbreeding. Maruthachalam Ravi and Simon Chan have now developed a simple method for producing haploid Arabidopsis thaliana via seeds that can be readily extended to crop plants. Previously haploid production involved tissue culture or genome elimination in wide crosses, and many species are intractable to these methods. The new technique involves engineering a single protein, the centromere-specific histone CENH3, to create strains whose genome is eliminated from the zygote after crossing to wild type. This generates haploid plants with chromosomes from the wild-type parent only. CENH3 plays a universal role at eukaryote centromeres, so in principle this should be transferable to all plant species. Making haploid plants — which inherit chromosomes from only one parent — is useful for genetic research and also, crucially, for plant breeding. A new method for generating haploid Arabidopsis plants is now described, involving the manipulation of a single centromeric protein, CENH3. When cenh3 null plants are crossed with wild-type plants, the mutant chromosomes are eliminated, producing haploid progeny. Production of haploid plants that inherit chromosomes from only one parent can greatly accelerate plant breeding 1 , 2 , 3 . Haploids generated from a heterozygous individual and converted to diploid create instant homozygous lines, bypassing generations of inbreeding. Two methods are generally used to produce haploids. First, cultured gametophyte cells may be regenerated into haploid plants 4 , but many species and genotypes are recalcitrant to this process 2 , 5 . Second, haploids can be induced from rare interspecific crosses, in which one parental genome is eliminated after fertilization 6 , 7 , 8 , 9 , 10 , 11 . The molecular basis for genome elimination is not understood, but one theory posits that centromeres from the two parent species interact unequally with the mitotic spindle, causing selective chromosome loss 12 , 13 , 14 . Here we show that haploid Arabidopsis thaliana plants can be easily generated through seeds by manipulating a single centromere protein, the centromere-specific histone CENH3 (called CENP-A in human). When cenh3 null mutants expressing altered CENH3 proteins are crossed to wild type, chromosomes from the mutant are eliminated, producing haploid progeny. Haploids are spontaneously converted into fertile diploids through meiotic non-reduction, allowing their genotype to be perpetuated. Maternal and paternal haploids can be generated through reciprocal crosses. We have also exploited centromere-mediated genome elimination to convert a natural tetraploid Arabidopsis into a diploid, reducing its ploidy to simplify breeding. As CENH3 is universal in eukaryotes, our method may be extended to produce haploids in any plant species.