Silver nanoparticles affect genes involved in ethylene signaling and stimulate root elongation of white mustard seedlings. 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. Overall design: Four treatments were used for RNA-seq: 1) water, 2) Ag NPs, 3) Ca(NO3)2 and 4) Ca(NO3)2 with Ag NPs

本研究聚焦于高浓度硝酸盐与银纳米颗粒（Ag NPs）存在条件下白芥的萌发过程。高浓度NO3-会抑制主根伸长，而Ag NPs可逆转该生长抑制效应；在正常培养条件下，Ag NPs亦可促进主根生长。对幼苗根系开展RNA测序（RNA-seq）分析发现，Ag NPs的存在会负向调控乙烯信号通路相关基因的表达。NO3-上调SAUR家族生长素响应基因，并下调多个生长素外排载体；而Ag NPs则下调与生长素生物合成相关的YUC9基因及部分SAUR家族基因。对比有无Ag NPs的高NO3-培养条件下萌发的幼苗转录组特征，结果显示：添加Ag NPs后，参与细胞壁生物发生、膜功能与发育的下调基因更少，而参与水杨酸与茉莉酸信号通路的上调基因也更少。不过，Ag NPs与NO3-均可上调参与多种胁迫响应（如病原菌胁迫、缺氧胁迫、氧化胁迫）以及木栓质与角质生物合成的基因表达。我们推测Ag NPs的生物学效应主要与乙烯及生长素信号通路相关。实验整体设计：本次RNA-seq共设置4组处理：1）蒸馏水对照组；2）Ag NPs处理组；3）硝酸钙（Ca(NO3)2）处理组；4）硝酸钙与Ag NPs联合处理组。