ARABIDOMICS-A new experimental platform for molecular analyses of plants in drop towers, on parabolic flights, and sounding rockets.

Plants represent an essential part of future life support systems that will enable human space travel to distant planets and their colonization. Therefore, insights into changes and adaptations of plants in microgravity are of great importance. Despite considerable efforts, we still know very little about how plants respond to microgravity environments on the molecular level, partly due to a lack of sufficient hardware and flight opportunities. The plant Arabidopsis thaliana, the subject of this study, represents a well-studied model organism in gravitational biology, particularly for the analysis of transcriptional and metabolic changes. To overcome the limitations of previous plant hardware that often led to secondary effects and to allow for the extraction not only of RNA but also of phytohormones and proteins, we developed a new experimental platform, called ARABIDOMICS, for exposure and fixation under altered gravity conditions. Arabidopsis seedlings were exposed to hypergravity during launch and microgravity during the free-fall period of the MAPHEUS 5 sounding rocket. Seedlings were chemically fixed inflight at defined time points, and RNA and phytohormones were subsequently analyzed in the laboratory. RNA and phytohormones extracted from the fixed biological samples were of excellent quality. Changes in the phytohormone content of jasmonate, auxin, and several cytokinins were observed in response to hypergravity and microgravity.

The fungal-specific ß-glucan-binding lectin FGB1 alters cell-wall composition and suppresses glucan-triggered immunity in plants.

ß-glucans are well-known modulators of the immune system in mammals but little is known about ß-glucan triggered immunity in planta. Here we show by isothermal titration calorimetry, circular dichroism spectroscopy and nuclear magnetic resonance spectroscopy that the FGB1 gene from the root endophyte Piriformospora indica encodes for a secreted fungal-specific ß-glucan-binding lectin with dual function. This lectin has the potential to both alter fungal cell wall composition and properties, and to efficiently suppress ß-glucan-triggered immunity in different plant hosts, such as Arabidopsis, barley and Nicotiana benthamiana. Our results hint at the existence of fungal effectors that deregulate innate sensing of ß-glucan in plants.