[HydroTropi]
Hydrotropism and Auxin-Inducible Gene Expression in Roots Grown under Microgravity Conditions

Biology and Biotechnology

Experiment Description
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ISS Science for Everyone

SCIENCE OBJECTIVES FOR EVERYONE

Hydrotropism and Auxin-Inducible Gene expression in Roots Grown Under Microgravity Conditions (HydroTropi) determines whether hydrotropic response can be used for the control of cucumber, Cucumis sativus, root growth orientation in microgravity.

SCIENCE RESULTS FOR EVERYONE

Gravity wins on Earth but water wins in space. This investigation examine the effects of gravity and water on cucumber roots to determine which response rules: hydrotropism – response to water – or gravitropism – response to gravity. Measurement of the growth and curvature of the roots and their gene expression showed that roots bent toward moisture in microgravity but grew straight along the direction of gravitational force at normal gravity. This sensitivity of roots to moisture gradients in microgravity may help regulate root growth for future plant production in space. The results also may help develop technology that enables plants to more efficiently uptake water here on Earth.

Experiment Description

RESEARCH OVERVIEW

The Hydrotropism and Auxin‐Inducible Gene expression in Roots Grown Under Microgravity Conditions (HydroTropi) experiment has three specific aims:

First, it demonstrates that gravitropism (a plant's ability to change its direction of growth in response to gravity) interferes with hydrotropism (a directional growth response in which the direction is determined by a stimuli in water concentration).
Second, it clarifies the differential auxin response that occurs during the respective tropisms (reaction of a plant to a stimulus), by investigating the auxin (compound regulating the growth of plants) inducible gene expression.
Third, it shows whether hydrotropism can be used in controlling root growth orientation in microgravity.

DESCRIPTION

Hydrotropism and Auxin‐Inducible Gene expression in Roots Grown Under Microgravity Conditions (HydroTropi) proposes to use the microgravity environment in space to separate hydrotropism from gravitropism and to dissect respective mechanisms in cucumber roots.

Media Gallery

Cucumber roots grew laterally in space following 70 hours in microgravity on STS-95. Image courtesy of JAXA.

NASA Image: ISS025E007780 - NASA astronaut Shannon Walker, Expedition 25 flight engineer, works with the Japan Aerospace Exploration Agency (JAXA) experiment HydroTropi (Hydrotropism & Auxin-Inducible Gene Expression in Roots Grown under Microgravity Conditions) in the Kibo laboratory of the International Space Station.

Applications

EARTH APPLICATIONS

HydroTropi provides a further understanding of how plants grow and develop at a molecular level, which can lead to significant advancements in agricultural production on Earth.

Publications

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PRINCIPAL INVESTIGATOR(S)

TAKAHASHI Hideyuki [Tohoku University]

JAXA’s Utilization Themes List

[HydroTropi]Hydrotropism and Auxin-Inducible Gene Expression in Roots Grown under Microgravity Conditions