Crop diseases threaten food security and sustainable agriculture. Consumption of crops containing nonessential toxic metals leads to health risks for humans. Therefore, cultivation of disease-resistant and toxic metal-safe crops is a double-gain strategy that can contribute to food security. Here, we show that rice heavy-metal transporter OsNRAMP1 plays an important role in plant immunity by modulating metal ion and reactive oxygen species (ROS) homoeostasis. OsNRAMP1 expression was induced after pathogenic bacteria and fungi infections. The osnramp1 mutants had an increased content of H 2 O 2 and activity of superoxide dismutase, but decreased activity of catalase, showing enhanced broad-spectrum resistance against bacterial and fungal pathogens. RNA-seq analysis identified a number of differentially expressed genes that were involved in metal ion and ROS homoeostasis. Altered expression of metal ion-dependent ROS-scavenging enzymes genes and lower accumulation of cations such as Mn together induced compromised metal ion-dependent enzyme-catalysing activity and modulated ROS homoeostasis, which together contributed towards disease resistance in osnramp1 mutants. Furthermore, the osnramp1 mutants contained lower levels of toxic heavy metals Cd and Pb and micronutrients Ni and Mn in leaves and grains. Taken together, a proof of concept was achieved that broad-spectrum disease-resistant and toxic heavy-metal-safe rice was engineered by removal of the OsNRAMP1 gene.
Rhyzopertha dominica (Fabricius) has developed extensive pesticide resistance in the last several decades. We have developed a supercritical fluid extraction method for Trigonella foenum-graecum L. (TFG) and studied the contact toxicities of the extracts to R. dominica. The extraction method was designed with orthogonal experiments to preserve and collect all the possible active components. Contact toxicity and efficiency of extraction were used as standard values to optimize extraction conditions, which were achieved at 55°C under 25 Mpa of pressure. The extraction efficiency for 200 g of dry sample reached 6.21% with 30 ml of 95% alcohol. Extracts loaded on filter paper showed dose and time dependent toxicities to adult R. dominica with a LC 50 value of 65.02 lg/cm 2 after 3 days post treatment. Our extensive in vivo studies indicated the extracts from Trigonella foenum-graecum seeds have high efficacy against pesticide resistant R. dominica. The active ingredient(s) from the extract shows promise as a novel pesticide candidate.
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