CENH3 from other species can can complement the cenh3-1 mutant of A. thaliana. The complemented plants look normal until crossed to the wild type, when they become haploid inducers. Maheshwari et al. show that a diverged CENH3 recognizes the same sequences as the endogenous one. This is surprising and inconsistent with expectations that CENH3 would coevolve with DNA targets. In addition, the authors describe the main active CEN repeat of A. thaliana
Takashi Akagi, Isabelle M. Henry, Takashi Kawai, Luca Comai, Ryutaro Tao
What happens when a dioecious species with X and Y chromosomes becomes polyploid? Cultivated persimmon does just that, managing to turn males into monoecious plants via epigenetic regulation of the sex determination gene MEGI. Epigenetic regulation provides flexibility for a polyploid with sex chromosomes.
Point Mutations in Centromeric Histone Induce Post-zygotic Incompatibility and Uniparental Inheritance
In a paper published in Plos Genetics the Britt Lab (Sundaram Kuppu et al.) and the Comai lab report a simple non-transgenic approach to the production of haploid inducers. Any of multiple changes in the conserved region of centromeric histone H3 is sufficient to yield a haploid inducer phenotype. This illustrates how simple variation at this locus can result in postzygotic incompatibility. This is a Simon Chan legacy paper.
In a paper published in the Plant Cell Isabelle Henry and collaborators from the Groover lab report the characterization of a mutant population of poplar produced by crossing Populus deltoides with irradiated pollen of P. nigra. The resulting F1 population of ~500 interspecific hybrids (soon to grow to ~800) provides in average 10 deletions and 3 insertions for every gene. The great phenotypic variation displayed will enable both the study of dosage-dependent regulation and the identification of dosage QTL in many traits.
In a paper in eLife published in May 2105 Han Tan and colleagues report that when Arabidopsis with weakened centromeres is crossed to the wild type, i.e. a plant with normal centromeres, the resulting embryos undergo chromothripsis, the cut-and-reassembly process leading to highly rearranged chromosomes. Because weakened centromeres can occur naturally, this process may contribute to the evolution of new chromosomes types. Additionally, this process can be manipulated genetically to provide a high frequency of haploids, a genetic type that accelerates plant breeding. Last, this provides an experimentally tractable system to study complex rearrangements associated with human diseases. This is a Simon Chan legacy paper.
Naturally Occurring Differences in CENH3 Affect Chromosome Segregation in Zygotic Mitosis of Hybrids
Genome elimination mediated by the chimeric “GFP-tailswap” CENH3 is a promising tool for the production of haploids. But, what is the significance of natural variation in CENH3? Shamoni Maheshwari et al. describe in PLoS Genetics (2015) how wide variation in CENH3 is compatible with its essential function, but epigenetically different centromeres do not function well when brought together in a hybrid embryo. This is a Simon Chan legacy paper.
Parental gene imprinting has been postulated to play a major role in postzygotic incompatibility. What happens to imprinted genes when two different species are mated? Diana Burkart-Waco et al. describe in PLoS One how paternally expressed genes (PEG) are frequently misregulated during interspecific hybridization.