Plant Molecular Biology

, Volume 67, Issue 1–2, pp 57–69 | Cite as

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

  • Mimi Tanimoto
  • Reynald Tremblay
  • Joseph ColasantiEmail author


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 Arabidopsis IDD 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.


Amyloplast Circumnutation Gravitropism Arabidopsis Starch Transcription factor 





Base pair




Dissociation element


Ethylene diamine tetraacetic acid










Iodine/potassium iodide




Landsberg erecta


Polymerase chain reaction




Reverse transcriptase polymerase chain reaction




Sodium dodecyl sulphate








Transfer DNA


Weight per volume


Zinc finger



We thank Michael Mucci for expert plant care and Elizabeth Holmes for performing DNA sequencing. Thanks also to Steven Chatfield, Steven Rothstein and Thierry Delatte for useful discussions, and Viktoriya Coneva for comments on the manuscript. MT was funded by the Ontario Ministry of Agriculture Challenge Fund and RT was a recipient of an Ontario Graduate Scholarship. Research in JC’s lab is supported by the Natural Sciences and Engineering Research Council of Canada (NSERC Discovery grant), the Canadian Foundation for Innovation, the Ontario Ministry of Agriculture and Food and the Ontario Innovation Trust.

Supplementary material

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)

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)


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Copyright information

© Springer Science+Business Media B.V. 2008

Authors and Affiliations

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

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