Biochemistry and Biotechnology Department, Kenyatta University, P, O, Box 43844, 00100 GPO, Nairobi, Kenya.
Plant Methods. 2012 Jun 21;8(1):20. doi: 10.1186/1746-4811-8-20.
Striga species are noxious root hemi-parasitic weeds that debilitate cereal production in sub-Saharan Africa (SSA). Control options for Striga are limited and developing Striga resistant crop germplasm is regarded as the best and most sustainable control measure. Efforts to improve germplasm for Striga resistance by a non-Genetic Modification (GM) approach, for example by exploiting natural resistance, or by a GM approach are constrained by limited information on the biological processes underpinning host-parasite associations. Additionaly, a GM approach is stymied by lack of availability of candidate resistance genes for introduction into hosts and robust transformation methods to validate gene functions. Indeed, a majority of Striga hosts, the world's most cultivated cereals, are recalcitrant to genetic transformation. In maize, the existing protocols for transformation and regeneration are tedious, lengthy, and highly genotype-specific with low efficiency of transformation.
We used Agrobacterium rhizogenes strain K599 carrying a reporter gene construct, Green Fluorescent Protein (GFP), to generate transgenic composite maize plants that were challenged with the parasitic plant Striga hermonthica. Eighty five percent of maize plants produced transgenic hairy roots expressing GFP. Consistent with most hairy roots produced in other species, transformed maize roots exhibited a hairy root phenotype, the hallmark of A. rhizogenes mediated transformation. Transgenic hairy roots resulting from A. rhizogenes transformation were readily infected by S. hermonthica. There were no significant differences in the number and size of S. hermonthica individuals recovered from either transgenic or wild type roots.
This rapid, high throughput, transformation technique will advance our understanding of gene function in parasitic plant-host interactions.
Striga 物种是有害的半寄生根杂草，会削弱撒哈拉以南非洲（SSA）的谷物生产。Striga 的控制选项有限，因此开发抗 Striga 的作物种质被认为是最佳和最可持续的控制措施。通过非遗传修饰（GM）方法，例如利用天然抗性，或通过 GM 方法来改善抗 Striga 种质的努力受到限制，因为对支持宿主-寄生虫关联的生物学过程的信息有限。此外，缺乏可用于引入宿主的候选抗性基因和稳健的转化方法来验证基因功能，这也阻碍了 GM 方法的应用。事实上，世界上大多数种植的谷物都是 Striga 的宿主，但它们对遗传转化具有抗性。在玉米中，现有的转化和再生方案繁琐、冗长，高度依赖于基因型，转化效率低。
我们使用携带报告基因构建体（绿色荧光蛋白，GFP）的根癌农杆菌 K599 菌株，生成了受到寄生植物 Striga hermonthica 挑战的转基因复合玉米植株。85%的玉米植株产生了表达 GFP 的转基因毛状根。与其他物种产生的大多数毛状根一致，转化的玉米根表现出毛状根表型，这是 A. rhizogenes 介导转化的标志。来自 A. rhizogenes 转化的转基因毛状根很容易被 S. hermonthica 感染。从转基因或野生型根中回收的 S. hermonthica 个体的数量和大小没有显著差异。
这种快速、高通量的转化技术将促进我们对寄生植物-宿主相互作用中基因功能的理解。
