Chapter 7
Gravitropism in Higher Plants: Molecular
Aspects
Klaus Palme, William Teale, and Franck Ditengou
Abstract The pervasive influence of gravity on life on Earth presents barriers to our
identifying and understanding of the signaling pathways which have evolved in
response to it. Plants are at the same time positively and negatively gravitropic,
using the Earth’s gravity to define their stature both above and below ground. Here
we review some of the signaling pathways which use the plant hormone auxin to carry
information on orientation from regions of perception to regions of growth response.
The regulation of these pathways is at once diverse and as yet poorly understood
but involves the control of members of a family of polarly localized cellular auxin
efflux carriers, the PINs, by factors such as phosphorylation. Auxin transport is also
influenced by the availability of calcium ions; this interaction is likely to emerge
as a key node in a plant’s responses to gravity. It is hoped that understanding the
mechanism of these responses will not only allow more efficient cultivation of plants in
space, but open paths to greater control over plant stature which will enable us, in the
future, better to respond to the challenges of feeding those of us still living on Earth.
Keywords Auxin · Higher plant gravitropism · Kinase signaling · Microgravity ·
Plant hormone
7.1 Introduction
On spaceship Earth, all evolution is governed by a 1-g environment. Different
organisms have evolved diverse strategies to monitor the gravitational field and
use it as a positional cue to orientate their growth. In this, plants are no exception:
they are sessile, but use gravity as a signal which integrates with other inputs (such as
light intensity and direction, humidity, touch and temperature), coordinating growth
to optimize access to light, water and nutrients. It is not surprising that plants are a
long-standing and important target for research into the mechanisms underlying
gravity perception and the gravity response. While cellular aspects of gravitropism
are discussed in Chap. 6, here we will discuss molecular aspects mostly unraveled in
Arabidopsis thaliana. The use of this fully sequenced and well characterized model
© The Author(s), under exclusive licence to Springer International Publishing AG,
part of Springer Nature 2018
M. Braun et al., Gravitational Biology I, SpringerBriefs in Space Life Sciences,
https://doi.org/10.1007/978-3-319-93894-3_7
93
Gravitropism in Higher Plants: Molecular
Aspects
Klaus Palme, William Teale, and Franck Ditengou
Abstract The pervasive influence of gravity on life on Earth presents barriers to our
identifying and understanding of the signaling pathways which have evolved in
response to it. Plants are at the same time positively and negatively gravitropic,
using the Earth’s gravity to define their stature both above and below ground. Here
we review some of the signaling pathways which use the plant hormone auxin to carry
information on orientation from regions of perception to regions of growth response.
The regulation of these pathways is at once diverse and as yet poorly understood
but involves the control of members of a family of polarly localized cellular auxin
efflux carriers, the PINs, by factors such as phosphorylation. Auxin transport is also
influenced by the availability of calcium ions; this interaction is likely to emerge
as a key node in a plant’s responses to gravity. It is hoped that understanding the
mechanism of these responses will not only allow more efficient cultivation of plants in
space, but open paths to greater control over plant stature which will enable us, in the
future, better to respond to the challenges of feeding those of us still living on Earth.
Keywords Auxin · Higher plant gravitropism · Kinase signaling · Microgravity ·
Plant hormone
7.1 Introduction
On spaceship Earth, all evolution is governed by a 1-g environment. Different
organisms have evolved diverse strategies to monitor the gravitational field and
use it as a positional cue to orientate their growth. In this, plants are no exception:
they are sessile, but use gravity as a signal which integrates with other inputs (such as
light intensity and direction, humidity, touch and temperature), coordinating growth
to optimize access to light, water and nutrients. It is not surprising that plants are a
long-standing and important target for research into the mechanisms underlying
gravity perception and the gravity response. While cellular aspects of gravitropism
are discussed in Chap. 6, here we will discuss molecular aspects mostly unraveled in
Arabidopsis thaliana. The use of this fully sequenced and well characterized model
© The Author(s), under exclusive licence to Springer International Publishing AG,
part of Springer Nature 2018
M. Braun et al., Gravitational Biology I, SpringerBriefs in Space Life Sciences,
https://doi.org/10.1007/978-3-319-93894-3_7
93