Plant Molecular Biology

, Volume 67, Issue 1, pp 57–69

Altered gravitropic response, amyloplast sedimentation and circumnutation in the Arabidopsisshoot gravitropism 5 mutant are associated with reduced starch levels

  • Mimi Tanimoto
  • Reynald Tremblay
  • Joseph Colasanti
Article

DOI: 10.1007/s11103-008-9301-0

Cite this article as:
Tanimoto, M., Tremblay, R. & Colasanti, J. Plant Mol Biol (2008) 67: 57. doi:10.1007/s11103-008-9301-0

Abstract

Plants have developed sophisticated gravity sensing mechanisms to interpret environmental signals that are vital for optimum plant growth. Loss of SHOOT GRAVITROPISM 5 (SGR5) gene function has been shown to affect the gravitropic response of Arabidopsis inflorescence stems. SGR5 is a member of the INDETERMINATE DOMAIN (IDD) zinc finger protein family of putative transcription factors. As part of an ongoing functional analysis of ArabidopsisIDD genes (AtIDD) we have extended the characterisation of SGR5, and show that gravity sensing amyloplasts in the shoot endodermis of sgr5 mutants sediment more slowly than wild type, suggesting a defect in gravity perception. This is correlated with lower amyloplast starch levels, which may account for the reduced gravitropic sensitivity in sgr5. Further, we find that sgr5 mutants have a severely attenuated stem circumnutation movement typified by a reduced amplitude and an decreased periodicity. adg1-1 and sex1-1 mutants, which contain no starch or increased starch, respectively, also show alterations in the amplitude and period of circumnutation. Together these results suggest that plant growth movement may depend on starch levels and/or gravity sensing. Overall, we propose that loss of SGR5 regulatory activity affects starch accumulation in Arabidopsis shoot tissues and causes decreased sensitivity to gravity and diminished circumnutational movements.

Keywords

AmyloplastCircumnutationGravitropismArabidopsisStarchTranscription factor

Abbreviations

ADG1

ADP-GLUCOSE PYROPHOSPHORYLASE 1

bp

Base pair

Col

Columbia

Ds

Dissociation element

EDTA

Ethylene diamine tetraacetic acid

GAPDH

GLYCERALDEHYDE-3-PHOSPHATE DEHYDROGENASE

ID1

INDETERMINATE1

IDD

INDETERMINATE Domain

GUS

β-Glucuronidase

IKI

Iodine/potassium iodide

kb

Kilobase

Ler

Landsberg erecta

PCR

Polymerase chain reaction

PGM

Phosphoglucomutase

RT-PCR

Reverse transcriptase polymerase chain reaction

SCR

SCARECROW

SDS

Sodium dodecyl sulphate

SEX1

STARCH EXCESS 1

SGR

SHOOT GRAVITROPISM

SHR

SHORT ROOT

T-DNA

Transfer DNA

w/v

Weight per volume

ZF

Zinc finger

Supplementary material

View video

Supplementary Fig. S1: Time-lapse movie of sgr5 circumnutation. Time-lapse movie of sgr5 mutant alleles in Col and Ler ecotypes. Images of plants growing under white fluorescent light were recorded every 5 min for 415 min and played back at 6 frames/s. Order of plants from left to right is sgr5-3, wild type (Col), sgr5-4 and wild type (Ler) (MOV 4500 kb)

View video

Supplementary Fig. S2: Time-lapse movie of circumnutation in starch mutants. Images of plants growing under fluorescent white light were captured every 5 min for 500 min and played back at 6 frames/s. From left to right plants are adg1-1, wild type (Col) and sex1-1 (MOV 3416 kb)

Copyright information

© Springer Science+Business Media B.V. 2008

Authors and Affiliations

  • Mimi Tanimoto
    • 1
  • Reynald Tremblay
    • 1
    • 2
  • Joseph Colasanti
    • 1
  1. 1.Department of Molecular and Cellular BiologyUniversity of GuelphGuelphCanada
  2. 2.Department of Biology, School of Graduate StudiesUniversity of Western OntarioLondonCanada