Plants exhibit a robust transcriptional response to gamma radiation which includes the induction of transcripts required for homologous recombination and the suppression of transcripts that promote cell cycle progression. Various DNA damaging agents induce different spectra of DNA damage as well as collateral damage to other cellular components and therefore are not expected to provoke identical responses by the cell. Here we study the effects of two different types of ionizing radiation (IR) treatment HZE (1 GeV Fe26+ high mass high charge and high energy relativistic particles) and gamma photons on the transcriptome of Arabidopsis thaliana seedlings. Both types of IR induce small clusters of radicals that can result in the formation of double strand breaks (DSBs) but HZE also produces linear arrays of extremely clustered damage. We performed these experiments across a range of time points (1.5-24 h after irradiation) in both wild-type plants and in mutants defective in the DSB-sensing protein kinase ATM. The two types of IR exhibit a shared double strand break-repair-related damage response although they differ slightly in the timing degree and ATM-dependence of the response. The ATM-dependent DNA metabolism-related transcripts of the DSB response were also induced by other DNA damaging agents but were not induced by conventional stresses. Both Gamma and HZE irradiation induced at 24 h post-irradiation ATM-dependent transcripts associated with a variety of conventional stresses; these were overrepresented for pathogen response rather than DNA metabolism. In contrast only HZE-irradiated plants at 1.5 h after irradiation exhibited an additional and very extensive transcriptional response shared with plants experiencing extended night. This response was not apparent in gamma-irradiated plants.

This study describes the transcriptional response of P. aeruginosa PAO1 to low-Earth orbit environmental conditions. Our aim was to assess whether the microgravity environment of spaceflight could induce virulence traits in P. aeruginosa. To this end P. aeruginosa cultures were grown in space and the expression profile was compared with ground control samples (both in biological triplicate). Characterization of bacterial behavior in the microgravity environment of spaceflight is of importance towards risk assessment and prevention of infectious disease during long-term missions. Further this research field unveils new insights into connections between low fluid-shear regions encountered by pathogens during their natural infection process in vivo and bacterial virulence. This study is the first to characterize the global transcriptomic and proteomic response of an opportunistic pathogen that is actually found in the space habitat Pseudomonas aeruginosa. Overall P. aeruginosa responded to spaceflight conditions through differential regulation of 167 genes and 28 proteins with Hfq identified as a global transcriptional regulator in the response to this environment. Since Hfq was also induced in spaceflight-grown Salmonella typhimurium Hfq represents the first spaceflight-induced regulator across the bacterial species border. The major P. aeruginosa virulence-related genes induced in spaceflight conditions were the lecA and lecB lectins and the rhamnosyltransferase (rhlA) involved in the production of rhamnolipids. The transcriptional response of spaceflight-grown P. aeruginosa was compared with our previous data of this organism grown in microgravity-analogue conditions using the rotating wall vessel (RWV) bioreactor technology. Interesting similarities were observed among others with regard to Hfq regulation and oxygen utilization. While LSMMG-grown P. aeruginosa mainly induced genes involved in microaerophilic metabolism P. aeruginosa cultured in spaceflight adopted an anaerobic mode of growth in which denitrification was presumably most prominent. Differences in hardware between spaceflight and LSMMG experiments in combination with more pronounced low fluid shear and mixing in spaceflight when compared to LSMMG conditions were hypothesized to be at the origin of these observations. Collectively our data suggest that spaceflight conditions could induce the transition of P. aeruginosa from an opportunistic organism to potential pathogen results that are of importance for infectious disease risk assessment and prevention both during spaceflight missions and in the clinic.

The purpose of this study was to search for microgravity-sensitive genes specifically for apoptotic genes influenced by the microgravity environment and other genes related to immune response. Experiment Overall Design: Two-group design with paired samples i.e. one 1G and one MMG culture came from the same donor. Therefore 6 samples came from 3 different donors. Experiment Overall Design: Donor 1 :GSM96146,GSM96147 Experiment Overall Design: Donor 2: GSM96148 GSM96149 Experiment Overall Design: Donor 3: GSM96150,GSM96151 Experiment Overall Design: Total RNA was submitted to and then labeled hybridized and data generated by the Baylor College Medicine Microarray Core Facility (333E One Baylor Plaza Houston TX 77030).

The purpose of this study was to search for microgravity-sensitive genes specifically for apoptotic genes influenced by the microgravity environment and other genes related to immune response. Experiment Overall Design: Two-group design with paired samples i.e. one 1G and one MMG culture came from the same donor. Therefore 6 samples came from 3 different donors. Experiment Overall Design: Donor 1 :GSM96146,GSM96147 Experiment Overall Design: Donor 2: GSM96148 GSM96149 Experiment Overall Design: Donor 3: GSM96150,GSM96151 Experiment Overall Design: Total RNA was submitted to and then labeled hybridized and data generated by the Baylor College Medicine Microarray Core Facility (333E One Baylor Plaza Houston TX 77030).

The purpose of this study was to search for microgravity-sensitive genes specifically for apoptotic genes influenced by the microgravity environment and other genes related to immune response. Experiment Overall Design: Two-group design with paired samples i.e. one 1G and one MMG culture came from the same donor. Therefore 6 samples came from 3 different donors. Experiment Overall Design: Donor 1 :GSM96146,GSM96147 Experiment Overall Design: Donor 2: GSM96148 GSM96149 Experiment Overall Design: Donor 3: GSM96150,GSM96151 Experiment Overall Design: Total RNA was submitted to and then labeled hybridized and data generated by the Baylor College Medicine Microarray Core Facility (333E One Baylor Plaza Houston TX 77030).