Search

The Arabidopsis homeodomain transcription factor SHOOT MERISTEMLESS (STM) is crucial for shoot apical meristem (SAM) function, yet the components and structure of the STMgene regulatory network (GRN) are largely unknown. Here, we showthat transcriptional regulators are overrepresented among STM-regulated genes and, using these as GRN components in Bayesian network analysis, we infer STM GRN associations and reveal regulatory relationships between STM and factors involved in multiple aspects of SAM function. These include hormone regulation, TCP-mediated control of cell differentiation, AIL/PLT-mediated regulation of pluripotency and phyllotaxis, and specification of meristem-organ boundary zones via CUC1. We demonstrate a direct positive transcriptional feedback loop between STM and CUC1, despite their distinct expression patterns in the meristemand organ boundary, respectively. Our further finding that STM activates expression of the CUC1-targeting microRNA miR164c combined with mathematical modelling provides a potential solution for this apparent contradiction, demonstrating that these proposed regulatory interactions coupled with STM mobility could be sufficient to provide a mechanism for CUC1 localisation at the meristem-organ boundary. Our findings highlight the central role for the STM GRN in coordinating SAM functions. [ABSTRACT FROM AUTHOR]

An abstract of the article concerning Knotted1-like homeobox (KNOX) genes which regulate plant development and diversity is presented.

Leaf development in higher plants requires the specification of leaf initials at the flanks of a pluripotent structure termed the shoot apical meristem. In Arabidopsis, this process is facilitated by negative interactions between class I KNOTTED1-like homeobox (KNOX) and ASYMMETRIC LEAVES1 (AS1) transcription factors, such that KNOX proteins are confined to the meristem and AS1 to leaf initials. Sites of leaf inception are also defined by local accumulation of the hormone auxin; however, it is unknown how auxin and AS1 activities are integrated to control leaf development. Here, we show that auxin and AS1 pathways converge to repress expression of the KNOX gene BREVIPEDICELLUS (BP) and thus promote leaf fate. We also demonstrate that regulated auxin gradients control leaf shape in a KNOX-independent fashion and that inappropriate KNOX activity in leaves perturbs these gradients, hence altering leaf shape. We propose that regulatory interactions between auxin, AS1 and KNOX activities may both direct leaf initiation and sculpt leaf form. [ABSTRACT FROM AUTHOR]