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Centromere Behavior Has Great Impact on Generation of New Wheat Germplasm
“The best hope for future crop improvements lies in exploiting the abundant gene pool of the plant's wild relatives.” wrote Moshe Feldman and Ernest R. Sears on January 1, 1981. The biggest bottleneck for wheat (Triticum spp.) breeding is the lack of the new available genetic resources.
In order to widen and improve such materials for breeding, Dr. HAN Fangpu’s group in the Institute of Genetics and Developmental Biology (IGDB), Chinese Academy of Sciences studied De Novo centromere formation and centromeric sequence expansion in wheat and its wide hybrids, which is with great importance for new translocation lines.
Dr. HAN’s group has been committed to research on the hybridization between wheat and its wild relatives. They try to answer whether repetitive sequences can be used for wheat breeding. Dr. Han’ group previously successfully selected different novel ploidy triticale and trititrigia lines which carried excellent disease-resistance genes (Guo et al. 2015, JGG). They work on wheat-Thinopyrum translocation lines to select materials with high resistance to Fusarium head blight. They also systematically studied the mechanism of chromosome variation and translocation formation in wheat and its wide hybrids. Preliminary results indicate that centromere misdivision can induce new translocation lines. The widely-used 1B/1R translocation lines around the world (about 70% of the wheat varieties contain this translocation chromosome) has a fusion centromere, half from rye (Secale cereal), and half from wheat.
They recently found that the wheat centromeric specific sequences (CRW) were strongly reduced or essentially lost in some wheat ditelosomic lines and in the addition lines from its wide hybrids. The ectopic genomic sequences were identified to incorporate the new centromeres in these lines with the methods of CENH3-ChIP-dot-blot alone or in combination with CENH3-ChIP-seq. De novo centromeres formation on chromosome arms induced by centromere misdivision were observed in the wheat-Thintermedium addition line TAI-14 and the chromosome of Thelongatum in the addition line derived from Tdurum Kekeruite × 8802.
Moreover, stable alien chromosomes with two and three regions containing CRW sequences induced by centromere breakage were observed in the wheat-Thelongatum hybrid derivatives. The rye centromeric specific sequences spread along the chromosome arms and may have caused centromere expansion in wheat-rye hybrids.
Centromere variation and activity in wheat aneuploids and its wide hybrids may be associated with chromosome stability, rearrangements, and novel chromosome formations. Thus, the centromere behavior in wide crosses likely has an important impact on the generation of biodiversity, which ultimately has implications for speciation.
The work entitled “De Novo Centromere Formation and Centromeric Sequence Expansion in Wheat and its Wide Hybrids” was published in PLOS Genetics on Apr 25, 2016 (doi:10.1371/journal.pgen.1005997).
This work was supported by grants from the National Natural Science Foundation of China and the Ministry of Science and Technology of China.
Centromere alterations occurred in aneuploid wheat and in wheat hybrids. (Image by IGDB)
Author contact:
Dr. HAN Fangpu