近日，華中農業大學小麥團隊蘇漢東教授課題組在《Molecular Biology and Evolution》雜志發表了“Centromere plasticity with evolutionary conservation and divergence uncovered by wheat 10+ genomes”的研究論文。該研究通過全球小麥育種計劃10+基因組材料的公共數據揭示了小麥著絲粒進化多樣性和功能保守性的協調機制，為著絲粒功能的可塑性提供新見解。
著絲粒是維持基因組穩定的關鍵染色體區域，富含高度相似的重復序列，同時也是基因組結構最復雜、變化最劇烈的區域，在進化過程中產生復雜的遺傳多樣性。在大多數真核生物中，快速變異的著絲粒序列可以促進核型進化和新物種形成。盡管著絲粒存在高度異質性，但尚不完全了解這些廣泛變異的序列是如何確保著絲粒功能的穩健。小麥是典型的異源六倍體作物，包含3套高度相似又存在差異的亞基因組，著絲粒對多倍體基因組的穩定尤為關鍵。
該研究以來自全球小麥育種計劃的10+品系群體為對象，系統解析了每個材料著絲粒的定位和序列組成。研究人員捕獲到小麥著絲粒重復序列、位置等存在大量變異，發現不同材料著絲粒存在廣泛的重定位現象。在不同材料中均發現與著絲粒重要表觀標記CENH3核小體緊密結合的重復序列是逆轉錄轉座子Cereba，并且系統發育結果表明在不同小麥品系中Cereba轉座子序列表現出較為一致的同質性，但結合程度較低的重復序列在每個小麥品系中表現出獨特性，這意味著存在特定機制選擇某些重復序列類型作為功能核心著絲粒的組成。此外，研究人員還觀察到CENH3核小體在復雜的著絲粒重復序列（包括重新定位的著絲粒）上顯示出較松散的DNA末端包裹，不同品系中嚴格的CENH3核小體占位和內在DNA序列特征在確定著絲粒功能方面發揮關鍵作用。這些結果表明，多種機制參與小麥10+基因組材料CENH3核小體的適應并穩定著絲粒功能。最終，研究人員提出在不同的基因組背景下著絲粒染色質具有明顯的表觀遺傳可塑性，并且由于過去的育種選擇，著絲粒的高穩健性對于維持小麥基因組穩定性至關重要。
我校植物科學技術學院碩士研究生馬桓和丁文濤為論文共同第一作者，小麥團隊鄢文豪教授、茆海亮教授、蘭彩霞教授、李強教授和陳偉教授對該研究進行了指導和建議。該研究得到國家重點研發計劃（2021YFF1000800）、國家自然科學基金（32170571）等項目資助。
蘇漢東課題組主要聚焦于小麥染色體生物學和合成基因組學的研究，探索小麥遠緣雜交和多倍化的遺傳機制，并利用人工染色體進行植物合成基因組學的探索。已在PNAS、Plant Cell、Genome Research、PLOS Biology、Molecular Biology and Evolution、Plant Biotechnology J、New Phytologist、Plant Journal、PLOS Genetics等領域內知名學術期刊發表研究論文20多篇。
論文鏈接：/file/upload/2023-08-19/0wozuqiv3cf
英文摘要：Centromeres are the chromosomal regions that play a crucial role in maintaining genomic stability. The underling highly repetitive DNA sequences can evolve quickly in most eukaryotes, and promote karyotype evolution. Despite their variability, it is not fully understood how these widely variable sequences ensure the homeostasis of centromere function. In this study, we investigated the genetics and epigenetics of centromeres in a population of wheat lines from global breeding programs. We captured a high degree of sequences, positioning, and epigenetic variations in the large and complex wheat centromeres. We found that the most CENH3-associated repeats are Cereba element of retrotransposons and exhibit phylogenetic homogenization across different wheat lines, but the less-associated repeat sequences diverge on their own way in each wheat line, implying specific mechanisms for selecting certain repeat types as functional core centromeres. Furthermore, we observed that CENH3 nucleosome structures display looser wrapping of DNA termini on complex centromeric repeats, including the repositioned centromeres. We also found that strict CENH3 nucleosome positioning and intrinsic DNA features play a role in determining centromere identity among different lines. Specific non-B form DNAs were substantially associated with CENH3 nucleosomes for the repositioned centromeres. These findings suggest that multiple mechanisms were involved in the adaptation of CENH3 nucleosomes that can stabilize centromeres. Ultimately, we proposed a remarkable epigenetic plasticity of centromere chromatin within the diverse genomic context, and the high robustness is crucial for maintaining centromere function and genome stability in wheat 10+ lines as a result of past breeding selections.
