Abstract
Nanoparticles are a class of newly emerging environmental pollutions. To date, few experiments have been conducted to investigate the effect nanoparticles may have on plant growth and development. It is important to study the effects nanoparticles have on plants because they are stationary organisms that cannot move away from environmental stresses like animals can, therefore they must overcome these stresses by molecular routes such as altering gene expression. microRNAs (miRNA) are a newly discovered, endogenous class of post-transcriptional gene regulators that function to alter gene expression by either targeting mRNAs for degradation or inhibiting mRNAs translating into proteins. miRNAs have been shown to mediate abiotic stress responses such as drought and salinity in plants by altering gene expression, however no study has been performed on the effect of nanoparticles on the miRNA expression profile; therefore our aim in this study was to classify if certain miRNAs play a role in plant response to Al2O3 nanoparticle stress. In this study, we exposed tobacco (Nicotiana tabacum) plants (an important cash crop as well as a model organism) to 0%, 0.1%, 0.5%, and 1% Al2O3 nanoparticles and found that as exposure to the nanoparticles increased, the average root length, the average biomass, and the leaf count of the seedlings significantly decreased. We also found that miR395, miR397, miR398, and miR399 showed an extreme increase in expression during exposure to 1% Al2O3 nanoparticles as compared to the other treatments and the control, therefore these miRNAs may play a key role in mediating plant stress responses to nanoparticle stress in the environment. The results of this study show that Al2O3 nanoparticles have a negative effect on the growth and development of tobacco seedlings and that miRNAs may play a role in the ability of plants to withstand stress to Al2O3 nanoparticles in the environment.
Highlights
Nanoparticles are classified as being materials in which at least one dimension of the material is less than 100 nanometers in diameter [1]
It is unknown that the regulatory mechanism under nanoparticle exposure. microRNAs, are a newly discovered highly-conserved, endogenous class of regulatory molecules that do not code for proteins [3,4]. miRNAs are approximately 20–22 nucleotides in length and work in post transcriptional gene regulation by either targeting messenger RNAs for degradation, or by inhibiting the translation of mRNAs [4]. miRNAs have been shown to aid in the regulation of many processes within plants such as leaf and root development, organ maturation, cell proliferation, flowering time, and abiotic stress response [5,6]
In the media containing 0.1% aluminum oxide nanoparticles, the average germination rate was 92.8% and the seeds grown in 0.5% aluminum oxide nanoparticles had an average germination rate of 96.0%
Summary
Nanoparticles are classified as being materials in which at least one dimension of the material is less than 100 nanometers in diameter [1]. The amount of research funding dedicated to nanoparticle environmental health and safety increased from $35 million in 2005, to $117 million in 2011 [1]. More research funding is being provided for nanoparticle environmental health and safety research, to date, few experiments have been performed to show the effects nanoparticles may have on the growth, development, and gene expression in plants. Recent studies have shown that miRNAs help to mediate the expression of more than 30% of protein coding genes [7,8] and this number is expected to increase as more miRNAs are discovered and their target mRNAs are identified
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