A DELLA in Disguise: SPATULA Restrains the Growth of the Developing Arabidopsis Seedling

Eve-Marie Josse, Yinbo Gan, Jordi Bou-Torrent, Kelly L Stewart, Alison D Gilday, Christopher E Jeffree, Fabián E Vaistij, Jaime F Martínez-García, Ferenc Nagy, Ian A Graham, Karen J Halliday

Research output: Contribution to journalArticlepeer-review

Abstract

The period following seedling emergence is a particularly vulnerable stage in the plant life cycle. In Arabidopsis thaliana, the phytochrome-interacting factor (PIF) subgroup of basic-helix-loop-helix transcription factors has a pivotal role in regulating growth during this early phase, integrating environmental and hormonal signals. We previously showed that SPATULA (SPT), a PIF homolog, regulates seed dormancy. In this article, we establish that unlike PIFs, which mainly promote hypocotyl elongation, SPT is a potent regulator of cotyledon expansion. Here, SPT acts in an analogous manner to the gibberellin-dependent DELLAs, REPRESSOR OF GA1-3 and GIBBERELLIC ACID INSENSITIVE, which restrain cotyledon expansion alongside SPT. However, although DELLAs are not required for SPT action, we demonstrate that SPT is subject to negative regulation by DELLAs. Cross-regulation of SPT by DELLAs ensures that SPT protein levels are limited when DELLAs are abundant but rise following DELLA depletion. This regulation provides a means to prevent excessive growth suppression that would result from the dual activity of SPT and DELLAs, yet maintain growth restraint under DELLA-depleted conditions. We present evidence that SPT and DELLAs regulate common gene targets and illustrate that the balance of SPT and DELLA action depends on light quality signals in the natural environment.
Original languageEnglish
Pages (from-to)1337-1351
Number of pages15
JournalPlant Cell
Volume23
Issue number4
DOIs
Publication statusPublished - Apr 2011

Keywords

  • Alleles
  • Arabidopsis
  • Arabidopsis Proteins
  • Basic Helix-Loop-Helix Transcription Factors
  • Cotyledon
  • Gene Expression Regulation, Plant
  • Genes, Plant
  • Gibberellins
  • Hypocotyl
  • Light
  • Models, Biological
  • Mutation
  • Oligonucleotide Array Sequence Analysis
  • Phenotype
  • Phytochrome B
  • Repressor Proteins
  • Seedling

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