Coping with the un-natural: Tracking transcriptional activation and macromolecular profiles in Arabidopsis under microplastic exposure

Abstract

The ocean's microplastic (MP) burden reflects the ultimate sink, yet plants are the key receivers of all sizes. However, just a few studies have been published so far have solely examined single-sized commercial PS, PE, and PET. Furthermore, commercially available disposable plastic petri usage and autoclave-sterilization of polymers with plant growth medium might affect the results when testing the premises. Here we show in-vitro phenotypic, metabolic, and transcriptional change schemes in the Arabidopsis under ozone sterilized individual polymer types of varying sizes (75-150 and 150-212 mu m) using authentic macro-plastic pieces in the environment. PS, PP and, PE exposed photosynthetically active young seedlings outperformed both sizes of PVC and PET. MP reformed transcriptional expression of functional protein families regulating redox and energy status, DNA synthesis, cell division/repair. Both PET sizes yielded more than 6-17-fold transcripts of one helix protein2 (OHP2) and A-type cyclins (CYCA3;2). While not a significant interaction between MP types and sizes was detected for pigments (p = 0.118), osmoprotectants (p = 0.979), reactive oxygen species (p = 0.065), cell membrane strength (p = 0.0850), and biomass (p = 0.115); the effect of different polymer types was found positively responsive on the root architecture (p < 0.001) and depending on what level of particle size is present, showing a significant interaction between polymers and their dimensions in triggered OHP2 and CYCA3;2 transcript abundance (p = 0.001). Changes in root structure, germination, osmotic balance, and redox status might be attributed to the strong release of chemical additives on plastics. Despite our limited understanding of how MPs impact the overall defense network, the findings provided here may be beneficial for future plant-MP interaction research at the gene and protein level.