Abstract
The DNA molecule is associated with the role of encoding information required to produce RNA which is translated into proteins needed by the cell. This encoding involves information transmission to offspring or to other organisms by horizontal transfer. However, despite the abundance of this molecule in both the cell and the environment, its physiological role seems to be restricted mainly to that of a coding and inheritance molecule. In this paper, we report a new physiological role for the DNA molecule as involved in protection against desiccation, in addition to its well-established main information transfer and other recently reported functions such as bio-film formation in eDNA form. Desiccation-tolerant microorganisms such as Microbacterium sp. 3J1 significantly upregulate genes involved in DNA synthesis to produce DNA as part of their defensive mechanisms to protect protein structures and functions from drying according to RNA-seq analysis. We have observed the intracellular overproduction of DNA in two desiccation-tolerant microorganisms, Microbacterium sp. 3J1 and Arthrobacter siccitolerans 4J27, in response to desiccation signals. In addition, this conclusion can be made from our observations that synthetic DNA protects two proteins from drying and when part of a xeroprotectant preparation, DNA from various organisms including desiccation-sensitive species, does the same. Removal of DNA by nuclease treatment results in absence of this additive protective effect. We validated this role in biochemical and biophysical assays in proteins and occurs in trans even with short, single chains of synthetically produced DNA.
Highlights
Drying is one of the major stressors that threatens life and the integrity of biomolecules
To analyze whether the DNA found after osmotic downshock was the result of bacterial lysis or whether it was newly synthesized in response to water stress, we added PMAxx to cultures of Microbacterium sp. 3J1, A. siccitolerans 4J27, and Pseudomonas putida KT2440 in presence of 50% PEG, as described in Section “PMAxx Labeling, RNA Extraction, cDNA Synthesis (RT-PCR), and Quantitative PCR.”
No statistical differences were found in the Quantitative PCR (qPCR) of the 16S rRNA gene of Microbacterium sp. 3J1 cultured with 50% PEG despite the addition of PMAxx showing that all DNA used as a template had an intracellular origin (Figure 1B)
Summary
Drying is one of the major stressors that threatens life and the integrity of biomolecules. The molecular mechanisms that allow anhydrobiotic organisms to withstand the lack of water are varied, but in general one of the first steps is the accumulation of protective substances termed xeroprotectants, which reduce. Other compounds act as xeroprotectants, such as polyols, amino acids and organic acids, which are generally rich in hydroxyl groups (Clegg et al, 1982; Crowe et al, 1998). These molecules are accumulated either by uptake or by cell production (da Costa et al, 1998). Together with other protective mechanisms, the accumulation of xeroprotectants reduces the Maillard (browning) reaction that occurs between free carbonyl groups in reducing sugars and primary amino groups in proteins, lipids, and nucleic acids under conditions of dryness (Hodge, 1953; Nursten, 1981)
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