Peanuts that keep aﬂatoxin at bay: a threshold that matters
Aﬂatoxin contamination in peanuts poses major challenges for vulnerable populations of subSaharan Africa and South Asia. Developing peanut varieties to combat preharvest Aspergillus ﬂavus infection and resulting aﬂatoxin contamination has thus far remained a major challenge, confounded by highly complex peanut–Aspergilli pathosystem. Our study reports achieving a high level of resistance in peanut by overexpressing (OE) antifungal plant defensins MsDef1 and MtDef4.2, and through host-induced gene silencing (HIGS) of aﬂM and aﬂP genes from the aﬂatoxin biosynthetic pathway. While the former improves genetic resistance to A. ﬂavus infection, the latter inhibits aﬂatoxin production in the event of infection providing durable resistance against different Aspergillus ﬂavus morphotypes and negligible aﬂatoxin content in several peanut events/lines well. A strong positive correlation was observed between aﬂatoxin accumulation and decline in transcription of the aﬂatoxin biosynthetic pathway genes in both OE-Def and HIGS lines. Transcriptomic signatures in the resistant lines revealed key mechanisms such as regulation of aﬂatoxin synthesis, its packaging and export control, besides the role of reactive oxygen species-scavenging enzymes that render enhanced protection in the OE and HIGS lines. This is the ﬁrst study to demonstrate highly effective biotechnological strategies for successfully generating peanuts that are near-immune to aﬂatoxin contamination, offering a panacea for serious food safety, health and trade issues in the semi-arid regions.