合成无融合生殖:从理论构想到杂种优势固定OA

Synthetic apomixis refers to use genetic engineering to resemble natural apomictic pathways to bypass meiosis and fertilization,enabling the production of clonal offspring through seeds that are genetically identical to the maternal parents.This technology involve two critical processes:1)the MiMe(mitosis instead of meiosis)system,which requires the simultaneous disruption of three genes to abolish the formation of DNA double-strand breaks for initiating homologous recombination,induce precocious separation of sister chromatids,and suppress the second meiotic division,thus leading to the generation of diploid gametes that are genetically identical to the parent;2)the induction of embryogenesis from these diploid gametes achieved either through ectopic expression of parthenogenesis-associated genes(e.g.,BBM1,PAR or HUAXU)or though the use of haploid inducers(e.g.,MTL,DMP or CENH3).The successful integration of these two modules produces clonal seeds with an identical genotype to the mother plant,thus achieving the fixation of heterosis.To date,the MiMe system has been successfully established in Arabidopsis thaliana,rice(Oryza sativa),tomato(Solanum lycopersicum),maize(Zea mays),rapeseed(Brassica napus),and sorghum(Sorghum bicolor),although the optimal combination of the three meiotic genes varies considerably among species.Efficient synthetic apomixis has so far been achieved only in rice,most notably through the"Fix"strategy,which has attained clonal seed induction efficiency of up to 99%.However,major challenges remain in extending this technology to other crops.This review systematically summarizes the molecular basis and species-specific optimization of the MiMe system,the diverse routes and efficiencies of parthenogenesis and haploid induction,synthetic apomixis and its applications in major crops.We further discuss critical challenges limiting broad application and offer perspectives on future directions for crop breeding.