Uncovering Transcriptional Responses to Fractional Gravity in Arabidopsis Roots

Abstract

Although many reports characterize the transcriptional response of Arabidopsis seedlings to microgravity, few investigate the effect of partial or fractional gravity on gene expression. Understanding plant responses to fractional gravity is relevant for plant growth on lunar and Martian surfaces. The plant signaling flight experiment utilized the European Modular Cultivation System (EMCS) onboard the International Space Station (ISS). The EMCS consisted of two rotors within a controlled chamber allowing for two experimental conditions, microgravity (stationary rotor) and simulated gravity in space. Seedlings were grown for 5 days under continuous light in seed cassettes. The arrangement of the seed cassettes within each experimental container results in a gradient of fractional g (in the spinning rotor). To investigate whether gene expression patterns are sensitive to fractional g, we carried out transcriptional profiling of root samples exposed to microgravity or partial g (ranging from 0.53 to 0.88 g). Data were analyzed using DESeq2 with fractional g as a continuous variable in the design model in order to query gene expression across the gravity continuum. We identified a subset of genes whose expression correlates with changes in fractional g. Interestingly, the most responsive genes include those encoding transcription factors, defense, and cell wall-related proteins and heat shock proteins.

Recent transcriptomic studies to elucidate the plant adaptive response to spaceflight and to simulated space environments

“…In addition, the day length is a factor that can regulate the plants flowering time, and it is even possible to use a genetic switch to induce flowering by adding a treatment, such as a heat shock ( Wang et al., 2022 ; Xie et al., 2022 ). Furthermore, it has been shown that the adaptive response of plants depends on both the level of gravity ( Herranz et al., 2019 ; Sheppard et al., 2021 )) and the time of exposure to the spatial environment ( Fengler et al., 2015 ; Kamal et al., 2019 )). In fact, an early and a late response can be identified in the adaptive response of plant cell cultures grown in simulated microgravity ( Kamal et al., 2019 ).…”

“…(2021) GLDS-314 1 g (Ground Control) white light 16h/dark 8h 4 days red light 2 days Col-0, nuc1-2 nuc2-2 Freeze −80°C Seedlings Manzano et al. (2020) GLDS-313 μ g , 0.53 g , 0.65 g and 0.88 g constant light 5 days Col-0 Freeze −80°C Root Sheppard et al. (2021) GLDS-223 Experiments performed in EMCS hardware, indicating the main characteristics of each of them: experimental conditions, genotype, fixation, tissue used to carry out the transcriptomic study, authors and the GeneLab Data Set (GLDS).…”

“…In addition, the identification of the biological functions or pathways of these 101 fractional- g responsive genes showed that they were genes involved in transcription regulation, chaperone function, cell wall and defense response. All of these categories had been previously described as being responsive to the plant response to the space environment ( Sheppard et al., 2021 ).…”

Simulated microgravity shapes the endophytic bacterial community by affecting wheat root metabolism

“…compared with Earth gravity (Colla et al, 2007;Sheppard et al, 2021). Moreover, plants are more susceptible to fungal pathogen infection under microgravity conditions (Qin et al, 2018).…”

“…However, the growth and resilience of plants in space environments, especially under microgravity, are compromised. Previous studies have demonstrated that plants exhibit significantly decreased cell wall synthesis (Levine et al ., 2001; Vandenbrink and Kiss, 2016; Sathasivam et al ., 2020), gene expression related to defence responses (Sheppard et al ., 2021), and increased susceptibility to pathogens under microgravity (Fu et al ., 2017). The effects of space microgravity on wheat have been attributed to multiple factors (Stutte et al ., 2006; Sheppard et al ., 2021), but the role of plant microbiota, and particularly root microbiota, has not been considered.…”