Masanga Joel Okoyo, Matheka Jonathan Mutie, Omer Rasha Adam, Ommeh Sheila Cecily, Monda Ethel Oranga, Alakonya Amos Emitati
Institute for Biotechnology Research, Jomo Kenyatta University of Agriculture and Technology, P.O. Box 62000-00200, Nairobi, Kenya.
Plant Cell Rep. 2015 Aug;34(8):1379-87. doi: 10.1007/s00299-015-1794-9. Epub 2015 Apr 21.
We report success of host-induced gene silencing in downregulation of aflatoxin biosynthesis in Aspergillus flavus infecting maize transformed with a hairpin construct targeting transcription factor aflR. Infestation of crops by aflatoxin-producing fungi results in economic losses as well as negative human and animal health effects. Currently, the control strategies against aflatoxin accumulation are not effective to the small holder farming systems in Africa and this has led to widespread aflatoxin exposure especially in rural populations of sub-Saharan Africa that rely on maize as a staple food crop. A recent strategy called host-induced gene silencing holds great potential for developing aflatoxin-resistant plant germplasm for the African context where farmers are unable to make further investments other than access to the germplasm. We transformed maize with a hairpin construct targeting the aflatoxin biosynthesis transcription factor aflR. The developed transgenic maize were challenged with an aflatoxigenic Aspergillus flavus strain from Eastern Kenya, a region endemic to aflatoxin outbreaks. Our results indicated that aflR was downregulated in A. flavus colonizing transgenic maize. Further, maize kernels from transgenic plants accumulated significantly lower levels of aflatoxins (14-fold) than those from wild type plants. Interestingly, we observed that our silencing cassette caused stunting and reduced kernel placement in the transgenic maize. This could have been due to "off-target" silencing of unintended genes in transformed plants by aflR siRNAs. Overall, this work indicates that host-induced gene silencing has potential in developing aflatoxin-resistant germplasm.
我们报道了在感染用靶向转录因子aflR的发夹构建体转化的玉米的黄曲霉中，宿主诱导的基因沉默在下调黄曲霉毒素生物合成方面取得的成功。产黄曲霉毒素的真菌侵染作物会导致经济损失以及对人类和动物健康产生负面影响。目前，针对黄曲霉毒素积累的控制策略对非洲的小农户农业系统无效，这导致黄曲霉毒素广泛暴露，尤其是在撒哈拉以南非洲依赖玉米作为主食作物的农村人口中。一种名为宿主诱导基因沉默的最新策略在为非洲背景开发抗黄曲霉毒素植物种质方面具有巨大潜力，在这种背景下，农民除了获得种质外无法进行进一步投资。我们用靶向黄曲霉毒素生物合成转录因子aflR的发夹构建体转化了玉米。用来自肯尼亚东部（黄曲霉毒素爆发的地方性区域）的产黄曲霉毒素的黄曲霉菌株对培育出的转基因玉米进行挑战。我们的结果表明，在定殖于转基因玉米的黄曲霉中aflR被下调。此外，转基因植物的玉米粒中黄曲霉毒素的积累水平比野生型植物的玉米粒低得多（14倍）。有趣的是，我们观察到我们的沉默盒导致转基因玉米发育迟缓并减少了籽粒排列。这可能是由于aflR小干扰RNA对转化植物中意外基因的“脱靶”沉默所致。总体而言，这项工作表明宿主诱导的基因沉默在开发抗黄曲霉毒素种质方面具有潜力。
