Spaceflight Induces Novel Regulatory Responses in Arabidopsis Seedling as Revealed by Combined Proteomic and Transcriptomic Analyses

Abstract

Background: Understanding of gravity sensing and response is critical to long-term human habitation in space and can provide new advantages for terrestrial agriculture. To this end, the altered gene expression profile induced by microgravity has been repeatedly queried by microarray and RNA-seq experiments to understand gravitropism. However, the quantification of altered protein abundance in space has been minimally investigated.Results: Proteomic (iTRAQ-labelled LC-MS/MS) and transcriptomic (RNA-seq) analyses simultaneously quantified protein and transcript differential expression of three-day old, etiolated Arabidopsis thaliana seedlings grown aboard the International Space Station along with their ground control counterparts. Protein extracts were fractionated to isolate soluble and membrane proteins and analyzed to detect differentially phosphorylated peptides. In total, 968 RNAs, 107 soluble proteins, and 103 membrane proteins were identified as differentially expressed. In addition, the proteomic analyses identified 16 differential phosphorylation events. Proteomic data delivered novel insights and simultaneously provided new context to previously made observations of gene expression in microgravity. There is a sweeping shift in post-transcriptional mechanisms of gene regulation including RNA-decapping protein DCP5, the splicing factors GRP7 and GRP8, and AGO4. These data also indicate AHA2 and FERONIA as well as CESA1 and SHOU4 as central to the cell wall adaptations seen in spaceflight. Patterns of tubulin-a 1, 3,4 and 6 phosphorylation further reveal an interaction of microtubule and redox homeostasis that mirrors osmotic response signaling elements. The absence of gravity also results in a seemingly wasteful dysregulation of plastid gene transcription. Conclusions: The datasets gathered from Arabidopsis seedlings exposed to microgravity revealed marked impacts on post-transcriptional regulation, cell wall synthesis, redox/microtubule dynamics, and plastid gene transcription. The impact of post-transcriptional regulatory alterations represents an unstudied element of the plant microgravity response with the potential to significantly impact plant growth efficiency and beyond. What’s more, addressing the effects of microgravity on AHA2, CESA1, and alpha tubulins has the potential to enhance cytoskeletal organization and cell wall composition, thereby enhancing biomass production and growth in microgravity. Finally, understanding and manipulating the dysregulation of plastid gene transcription has further potential to address the goal of enhancing plant growth in the stressful conditions of microgravity.

Functional mapping of gravitropism and phototropism for a desert tree, Populus euphratica

“…With the help of transcriptomic and proteomic technique, genes related to phosphorylation event, cell wall adaptations, microtubule and redox homeostasis interaction, photosynthesis, porphyrin, and chlorophyll metabolism were identified. These results had deeply aided our understanding on mechanism of plant tropism [16,51]. Significantly, in microgravity experiment, a connection between gravity response and the phototropical growth was built through the phototropic stimuli, suggesting the mutually inseparable role between phototropism and gravitropism [16].…”

“…To avoid the randomness with the model result, a cohesive connection between genes revealed in this work had been constructed through Gene Ontology analysis. Combining genes achieved from univariate model, bivariate model, composite model, first, genes for cell wall composition, e.g., ALTERED XYLOGLU-CAN 4-like (AXY4L), wall-associated receptor kinase-like 1 (WAKL1), QWRF, UBQ, has the potential to enhance cytoskeletal organization and cell wall composition, during the establishment process of gravitropism and gravitropism [51]. AXYL4 and WAKL1 respectively found with the stem and taproot trait might probably indicate their physically supportive roles in strengthening these two tropism.…”

Root growth direction in simulated microgravity is modulated by a light avoidance mechanism mediated by flavonols

“…It is possible that the mechanisms activated in response to microgravity overlap with mechanisms induced during hypoxia. Moreover, the plastid genome overexpression found in multiple transcriptomic studies of A. thaliana seedlings grown in space (Angelos et al, 2021; Kruse et al, 2020; Vandenbrink et al, 2019; Villacampa, Ciska, et al, 2021; Villacampa, Sora, et al, 2021), suggests an affected retrograde signaling, which is a critical step in chloroplast development and maintenance. Impairment of chloroplast development in microgravity could also lead to skotomorphogenesis‐like growth pattern (Vinti et al, 2000).…”

Cut the noise or couple up: Coordinating circadian and synthetic clocks

“…Organization of cells into complex assemblies of specialized tissues and organs is an emergent property of multicellularity. For such systems to function, coordination at every level is important; dysregulation in multicellular organisms is associated with dysfunctional, diseased or aged states (Guseman et al, 2010;Medina and Herranz, 2010;Li et al, 2015;Rosario et al, 2018;Dansereau et al, 2019;Karin et al, 2020;Kruse et al, 2020;Salas-Gonza ´lez et al, 2021). With circadian clocks present in most cells of multicellular life, it follows that these would also be coordinated.…”