Page Banner

United States Department of Agriculture

Agricultural Research Service

Title: The Gibberellin Pathway Mediates Knotted1-Type Homeobox Function in Plants with Different Body Plans

Authors
item Hay, Angela - ARS-UCB PLNT GENE EXP CTR
item Kaur, Hardip - PLANT SCI, OXFORD UNIV UK
item Phillips, Andrew - DEPT AGR SCI, BRISTOL UK
item Hedden, Peter - DEPT AGR SCI, BRISTOL UK
item Hake, Sarah
item Tsiantis, Miltos - ARS-UCB PLNT GENE EXP CTR

Submitted to: Current Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 18, 2002
Publication Date: September 17, 2002
Citation: HAY, A., KAUR, H., PHILLIPS, A., HEDDEN, P., HAKE, S.C., TSIANTIS, M. THE GIBBERELLIN PATHWAY MEDIATES KNOTTED1-TYPE HOMEOBOX FUNCTION IN PLANTS WITH DIFFERENT BODY PLANS. CURRENT BIOLOGY. 2002. 12:18:1557-1565.

Interpretive Summary: Current evidence suggests that the precise regulation of KNOTTED1-like homeobox (KNOX) transcription factors is central to the acquisition of leaf versus meristem identity in a wide spectrum of plant species. We show that reduced activity of the gibberellin (GA) growth regulator pathway promotes meristematic activity, both in the natural context of KNOX function in the SAM and upon ectopic KNOX expression in Arabidopsis leaves. We suggest that repression of GA activity by KNOX transcription factors is a key component of meristem function.

Technical Abstract: BACKGROUND: The shoot apical meristem (SAM) is an indeterminate structure that gives rise to the aerial parts of higher plants. Leaves arise from the differentiation of cells at the flanks of the SAM. Current evidence suggests that the precise regulation of KNOTTED1-like homeobox (KNOX) transcription factors is central to the acquisition of leaf versus meristem identity in a wide spectrum of plant species. Factors required to repress KNOX gene expression in leaves have recently been identified. Additional factors such as the CHD3 chromatin remodeling factor PICKLE (PKL) act to restrict meristematic activity in Arabidopsis leaves without repressing KNOX gene expression. Less is known regarding downstream targets of KNOX function. Recent evidence, however, has suggested that growth regulators may mediate KNOX activity in a variety of plant species. RESULTS: Here we show that reduced activity of the gibberellin (GA) growth regulator pathway promotes meristematic activity, both in the natural context of KNOX function in the SAM and upon ectopic KNOX expression in Arabidopsis leaves. We show that constitutive signaling through the GA pathway is detrimental to meristem maintenance. Furthermore, we provide evidence that one of the functions of the KNOX protein SHOOTMERISTEMLESS (STM) is to exclude transcription of the GA-biosynthesis gene AtGA20ox1 from the SAM. We also demonstrate that AtGA20ox1 transcript is reduced in the pkl mutant in a KNOX-independent manner. Moreover, we show a similar interaction between KNOX proteins and GA-biosynthesis gene expression in the tomato leaf and implicate this interaction in regulation of the dissected leaf form. CONCLUSIONS: We suggest that repression of GA activity by KNOX transcription factors is a key component of meristem function. Transfer of the KNOX/GA regulatory module from the meristem to the leaf may have contributed to the generation of the diverse leaf morphologies observed in higher plants.

Last Modified: 12/22/2014
Footer Content Back to Top of Page