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

TY - JOUR

T1 - A DELLA in Disguise

T2 - SPATULA Restrains the Growth of the Developing Arabidopsis Seedling

AU - Josse, Eve-Marie

AU - Gan, Yinbo

AU - Bou-Torrent, Jordi

AU - Stewart, Kelly L.

AU - Gilday, Alison D.

AU - Jeffree, Christopher E.

AU - Vaistij, Fabian E.

AU - Martinez-Garcia, Jaime F.

AU - Nagy, Ferenc

AU - Graham, Ian A.

AU - Halliday, Karen J.

PY - 2011/4

Y1 - 2011/4

N2 - 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.

AB - 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.

KW - PLANT PHOTORECEPTORS PHYTOCHROME

KW - TRANSCRIPTION FACTOR SPATULA

KW - LOOP-HELIX PROTEIN

KW - NEGATIVE REGULATOR

KW - GIBBERELLIN RECEPTOR

KW - MEDIATED DEGRADATION

KW - SIGNAL-TRANSDUCTION

KW - FLORAL DEVELOPMENT

KW - INTERACTING FACTOR

KW - LOCUS ENCODES

UR - http://www.scopus.com/inward/record.url?scp=79957678085&partnerID=8YFLogxK

U2 - 10.1105/tpc.110.082594

DO - 10.1105/tpc.110.082594

M3 - Article

SN - 1040-4651

VL - 23

SP - 1337

EP - 1351

JO - The Plant Cell

JF - The Plant Cell

IS - 4

ER -