PNAS：玉米中制造基因工程迷你染色体的新技术

生物谷

生物谷报道：哥伦比亚大学的研究人员最近获得一种在玉米中制造工程迷你染色体（minichromosomes）的技术。因为研究人员能够在这种染色体上附加额外的基因，以研制具有抗病毒、昆虫、真菌和除草剂多重抗性的农作物，为研制治疗人类疾病的蛋白和代谢物带来新的希望。本篇研究刊载于PNAS中。

研究作者WeichangYu和JamesA.Birchler等证明基因可以堆栈在迷你染色体中。迷你染色体是一种极其微小的染色体。天然染色体由着丝粒、端粒和许多插入DNA组成，迷你染色体只含有着丝粒和端粒，却能接受附加新基因。

虽然在植物中制作人工染色体没有成功，但却首次得到了迷你染色体。尽管在植物中还有其它形式遗传修饰，但迷你染色体的功能更加强大，因为研究人员能够在迷你染色体添加许多基因，并操作这些基因。传统的遗传修饰法较复杂，研究人员几乎不能控制基因在染色体上的定位，不能将多个基因添加在彼此独立的染色体上。

研究人员可以通过将基因堆积在迷你染色体上，制造具有多重优势特征的农作物，如抗旱、抗病毒和抗虫农作物。另外，迷你染色体可以用于生产有医疗价值的多重外源蛋白和代谢物。玉米富含蛋白的胚乳，可以用来生产动物蛋白和人类抗体，因此迷你染色体能够更好地生产这些外源蛋白和抗体。另外，研究人员还可以利用迷你染色体发展生物燃料植物。

(资料来源 : Bio.com)

原始出处:

Published online before print May 14, 2007, 10.1073/pnas.0700932104
PNAS | May 22, 2007 | vol. 104 | no. 21 | 8924-8929

BIOLOGICAL SCIENCES / GENETICS
Construction and behavior of engineered minichromosomes in maize

Weichang Yu, Fangpu Han, Zhi Gao, Juan M. Vega*, and James A. Birchler ${dagger}$

Division of Biological Sciences, 117 Tucker Hall, University of Missouri, Columbia, MO 65211

Edited by Susan R. Wessler, University of Georgia, Athens, GA, and approved April 12, 2007 (received for review February 1, 2007)

Engineered minichromosomes were constructed in maize by modifying natural A and supernumerary B chromosomes. By using telomere-mediated chromosomal truncation, it was demonstrated that such an approach is feasible for the generation of minichromosomes of normal A chromosomes by selection of spontaneous polyploid events that compensate for the deficiencies produced. B chromosomes are readily fractionated by biolistic transformation of truncating plasmids. Foreign genes were faithfully expressed from integrations into normal B chromosomes and from truncated miniB chromosomes. Site-specific recombination between the terminal transgene on a miniA chromosome and a terminal site on a normal chromosome was demonstrated. It was also found that the miniA chromosome did not pair with its progenitor chromosomes during meiosis, indicating a useful property for such constructs. The miniB chromosomes are faithfully transmitted from one generation to the next but can be changed in dosage in the presence of normal B chromosomes. This approach for construction of engineered chromosomes can be easily extended to other plant species because it does not rely on cloned centromere sequences, which are species-specific. These platforms will provide avenues for studies on plant chromosome structure and function and for future developments in biotechnology and agriculture.

artificial chromosomes | FISH | genetic engineering | telomere truncation

Fig. 1. Minichromosome R2 produced by telomere truncation of an A chromosome. (A and B) Minichromosome R2 in a tetraploid (A) and a diploid (B) plant. Centromere and NOR are labeled green; truncating transgene is labeled red. Arrowhead denotes R2. Insets in A shows transgene (Top), CentC (Middle), and the merged (Bottom) images of R2. Inset in B shows an enlarged merged image of R2. (C–E) R2 minichromosome in meiotic cells. CentC and knob are labeled green. Transgene is labeled red. R2 was not paired with other chromosomes at pachynema (C), diakinesis (D), and metaphase I (E). (F) Homozygote of R2. Enlarged images of R2 are shown in Insets. Transgenes are labeled red. Arrowheads denote chromosomes enlarged in Insets. (Scale bars, 10 µm.)