Uncovering Transcriptional Responses to Fractional Gravity in Arabidopsis Roots

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.

Space botany in Lithuania. II. Study on root gravity sensing during satellite “Bion- 11” flight / Kosminė botanika Lietuvoje. II. Šaknų gravitacijos jutimo tyrimas palydovo „Bion-11“ skrydžio metu

This paper addresses the space experiments performed on board of the unmanned satellite “Bion-11” in 1997. To detail root gravity sensing in stimulus-free microgravity environment, researchers from the Institute of Botany developed an automatically operating centrifuge “Neris-8” to grow garden cress seedlings and to chemically fix them at the end of the experiments. There was examined behaviour of gravity sensors - amyloplasts within cap cells of roots responding to stimulation by artificial fractional gravity. The static of amyloplasts was determined in roots after continuous growth for 25 h in microgravity, 0.005, 0.02, 0.1 and 1-g environment. The movement kinetics of amyloplasts was studied in roots during the exposition to microgravity after 24-h growth in 1-g environment or conversely. Quantitative study on the patterns of positioning and movement of plastids was performed by light microscopy. The results obtained led us to detail a mode of gravity sensing by roots in which the interactions between moving amyloplasts, cytoplasm and cytoskeleton were discussed.

Constant curvature coefficients and exact solutions in fractional gravity and geometric mechanics

We present a study of fractional configurations in gravity theories and Lagrange mechanics. The approach is based on a Caputo fractional derivative which gives zero for actions on constants. We elaborate fractional geometric models of physical interactions and we formulate a method of nonholonomic deformations to other types of fractional derivatives. The main result of this paper consists of a proof that, for corresponding classes of nonholonomic distributions, a large class of physical theories are modelled as nonholonomic manifolds with constant matrix curvature. This allows us to encode the fractional dynamics of interactions and constraints into the geometry of curve flows and solitonic hierarchies.