Plant Molecular Defense Mechanisms Promoted by Nanoparticles against Environmental Stresses

The alleviation of environmental stress on plants by the application of nanoparticles (NPs) has been a significant trend in the agricultural research of the last decade. Various sources of stress, such as salinity, drought, flooding, low and high temperatures, light, darkness, heavy metals, and microbial pathogens have been shown to be mitigated by NPs. Changes in gene expression associated with NP-based alleviation, however, have not been fully investigated, and the molecular defense mechanisms associated with the enhancement of plant tolerance by NPs need to be better understood. To this end, this paper reviews all available reports regarding plant transcriptomic and proteomic responses to NP-based alleviation of stress conditions. Despite their limited number, these reports discuss molecular defense mechanisms promoted by NPs under stress. Selected studies targeted salinity, drought, flooding, cold, heavy metal cadmium (Cd), fluoride and the antibiotic tetracycline (TC) as sources of abiotic stress, as well as biotic stress caused by pathogens in addition to wounding in plant tissues which might due to abiotic or biotic factors. From these studies, large number of genes appears to be responsive to NPs under stress, suggesting that unique molecular defense patterns arise from the combination of NP treatment and environmental stress. Moreover, transcriptional repression is shown to be the basic molecular mechanism of the plant response to NPs, regardless of type or size. This review provides an illustration of the molecular defense mechanisms promoted by NPs for plants suffering from abiotic or biotic stresses. (C) 2019 Friends Science Publishers