Silver nanoparticles affect genes involved in ethylene signaling and stimulate root elongation of white mustard seedlings

This work was focused on the germination of white mustard in the presence of high concentration of nitrate and silver nanoparticles (Ag NPs). High NO3- reduced primary root length while Ag NPs reversed the growth inhibition. Ag NPs increased root length also under normal conditions. RNA-seq of the seedling roots revealed that the presence of Ag NPs negatively affected the expression of genes involved in the ethylene signaling pathway. NO3- up-regulated auxin-responsive genes from SAUR family and down-regulated several auxin efflux carries, while Ag NPs down-regulated YUC9 associated with auxin biosynthesis and some SAUR genes. Comparison of transcriptional profiles of seedlings germinated on high NO3- with and without Ag NPs indicated that in the presence Ag NPs fewer genes involved in cell wall biogenesis and membrane functions and development were down-regulated and fewer genes involved in salicylic and jasmonic acid signaling were up-regulated. However, both Ag NPs and NO3- increased the expression of genes involved in response to various stresses (e.g. pathogens, hypoxia, oxidative stress) and suberin and cutin biosynthesis. We assume that the effect of Ag NPs was primarily related to the ethylene and auxin signaling pathways. Four treatments were used for RNA-seq: 1) water, 2) Ag NPs, 3) Ca(NO3)2 and 4) Ca(NO3)2 with Ag NPs