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

Abstract

Discovering the adaptation mechanisms of plants to the space environment is essential for supporting human space exploration. Transcriptomic analyses allow the identification of adaptation response pathways by detecting changes in gene expression at the global genome level caused by the main factors of the space environment, namely altered gravity and cosmic radiation. This article reviews transcriptomic studies carried out from plants grown in spaceflights and in different ground-based microgravity simulators. Despite differences in plant growth conditions, these studies have shown that cell wall remodeling, oxidative stress, defense response, and photosynthesis are common altered processes in plants grown under spaceflight conditions. European scientists have significantly contributed to the acquisition of this knowledge, e.g., by showing the role of red light in the adaptation response of plants (EMCS experiments) and the mechanisms of cellular response and adaptation mostly affecting cell cycle regulation, using cell cultures in microgravity simulators.

Keywords: Microgravity sciences; Omics; Plant biology; Space sciences.

Graphical abstract

Figure 1

Distribution of Plant Space Omics contributions submitted to the GeneLab database Most European contributions (in bold) have been done using cell culture experiments in simulated microgravity facilities (10% of the experiments) and the European Modular Cultivation System (EMCS) into the ISS (17% of the experiments). Other facilities frequently used in spaceflight experiments are the Biological Research in Canisters (BRIC) hardware and the VPS-VEGGIE cultivation chamber. At the top and the bottom part of the figure, images of some of the different facilities used are shown. From left to right and from top to bottom: Random Positioning Machine (credit ESA), Magnetic Levitation Instrument (credit Nottingham University) BRIC (credit NASA), Large Diameter Centrifuge (credit ESA), EMCS (credit ESA/NASA) and VEGGIE (credit NASA).

Figure 2

The main spaceflight-related genes Transcriptomic analyses of the numerous space experiments have so far identified a set of genes whose expression is altered by the spaceflight environment in a similar way among the different experiments. The genes were grouped according to the function of their proteins. (N) nucleus, (P) plastid, (M) mitochondria, (PR protein) pathogenesis related protein, (ROS) reactive oxygen species, (HSF) heat shock factor, (HSP) heat shock protein.

Figure 3

Proposed model of the microgravity adaptation mechanism in Arabidopsis thaliana Microgravity is perceived by the plant as an abiotic stress factor which activates the production of ROS. The signal, which is perceived at the plasma membrane, is then transmitted via Ca2+, MAPKs and phytohormones (auxin) to the nucleus where it triggers TFs like HSF. The TFs then regulate the expression of a set of genes that trigger molecular, cellular and physiological responses, leading to the establishment of the plant adaptation to the spaceflight environment. (ROS) reactive oxygen species, (TFs) transcription factors, (HSF) heat shock factor, (HSP) heat shock protein.