![]() Technologies have been developed to overcome hybridization barriers to broaden genetic resources for plant breeding. Pre-zygotic barriers include spatial and temporal separation, morphologically and ethologically floral isolation, and failure in pollen-pistil interactions. Hybridization barriers are generally divided into pre-zygotic and post-zygotic barriers. Thus, the evolution of CENH3 could contribute to hybridization barrier that prevents genetic cross between distantly related plant species. thaliana N-terminal tail and the L.oleraceum HFD acted normally as the Arabidopsis CENH3. thaliana caused chromosome missegregation and genome elimination, while the reversely swapped chimeric CENH3 with the A. ![]() Domain swap experiments showed that chimeric CENH3 with the N-terminal tail from Lepidium oleraceum and the HFD from A. Two regions of CENH3 protein are highly variable: N-terminal tail for kinetochore assembly and the loop 1 region which interacts with nucleosomal DNA and is crucial for centromere targeting and the recognition between CENH3 and centromeric DNA sequence. Thus, maize chromosomes can be retained in the oat genetic background. In contrast, in the oat/maize addition lines, oat CENH3 can nucleate functional kinetochores on maize chromosomes while the maize CENH3 gene is silenced. Chromosome elimination has also been reported in the unstable interspecific barley hybrids caused by the loss of CENH3 protein and centromere inactivation. The chromosome elimination is always on chromosomes from the hybridization parent that expresses the divergent CENH3. For example, haploid Arabidopsis plant could be produced by chromosome elimination when a wide type plant was crossed with a cenh3 mutant expressing an engineered CENH3 or naturally occurring CENH3 from distant related plant species. It plays an important role in chromosome behaviors during cell divisions, especially in chromosome elimination and adaptation. CENH3 is only 50% identical to canonical histone H3 in the histone fold domain (HFD). Immunostaining of wmCENH3-RFP and ZmCENH3-YFP in early stage somatic hybrid cells indicated that both wmCENH3-RFP and ZmCENH3-YFP proteins were expressed, but their binding patterns changed from the commonly observed dotted patterns to diffused ones, suggesting that the inactivation of CENH3 might be a factor for chromosome elimination in wheat/maize somatic hybridization.Ĭentromeric histone H3 (CENH3) is a variant to replace canonical histone H3 nucleosome in functional centromere for kinetochore assembly. Cytological and FISH analyses of somatic hybrid cells showed the formation of micronuclei and lagging chromatin in both somatic hybridizations with or without the wmCENH3- RFP transgene, indicating that ectopically expressed wmCENH3 could not overcome chromosome elimination in wheat/maize somatic hybrids. Somatic hybridization was performed between wmCENH3- RFP transgenic wheat and transgenic maize that expressed a ZmCENH3- YFP gene to investigate chromosome behaviors in somatic hybrids. The expressed wmCENH3-RFP was localized to nuclei as dotted patterns, indicating its targeting to wheat centromeres. ![]() The expression of ZmCENH3-YFP was not observed, while the expression of wmCENH3-RFP could be detected by RT-PCR, direct fluorescence microscopy, and immunostaining with anti-RFP antibody. Transgenic wheat plants with both ZmCNEH3- YFP and wmCENH3- RFP genes were identified by PCR. In this study, a maize full length CENH3 with a yellow fluorescent protein ( YFP) tag at C-terminus ( ZmCENH3- YFP) and a synthetic hybrid wmCENH3 with the N-terminus from wheat CENH3 and the histone fold domain (HFD) from maize tagged with a red fluorescent protein ( RFP) at the C-terminus (wmCENH3- RFP) were transformed to wheat by biolistics transformation. CENH3 is also important in the recognition of alien centromeres and determines the accommodation or elimination of alien chromosomes in interspecific or intergenic hybridization. Centromere-specific histone H3 (CENH3) replaces the canonical histone H3 in nucleosomes of functional centromeres, and plays important roles in faithful chromosome segregation during cell division. ![]()
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