TOPOISOMERASE 6B is involved in chromatin remodelling associated with control of carbon partitioning into secondary metabolites and cell walls, and epidermal morphogenesis in Arabidopsis.

Plant growth is continuous and modular, a combination that allows morphogenesis by cell division and elongation and serves to facilitate adaptation to changing environments. The pleiotropic phenotypes of the harlequin (hlq) mutant, isolated on the basis of ectopic expression of the abscisic acid (ABA)- and auxin-inducible proDc3:GUS reporter gene, were previously characterized. Mutants are skotomorphogenic, have deformed and collapsed epidermal cells which accumulate callose and starch, cell walls abundant in pectins and cell wall proteins, and abnormal and reduced root hairs and leaf trichomes.

Actin-based cellular framework for glucose signaling by Arabidopsis hexokinase1.

Glucose functions in plants both as a metabolic resource as well as a hormone that regulates expression of many genes. Arabidopsis hexokinase1 (HXK1) is the best understood plant glucose sensor/transducer, yet we are only now appreciating the cellular complexity of its signaling functions. We have recently shown that one of the earliest detectable responses to plant glucose treatments are extensive alterations of cellular F-actin.

A role for F-actin in hexokinase-mediated glucose signaling.

HEXOKINASE1 (HXK1) from Arabidopsis (Arabidopsis thaliana) has dual roles in glucose (Glc) signaling and in Glc phosphorylation. The cellular context, though, for HXK1 function in either process is not well understood. Here we have shown that within normal experimental detection limits, AtHXK1 is localized continuously to mitochondria.

Harlequin (hlq) and short blue root (sbr), two Arabidopsis mutants that ectopically express an abscisic acid- and auxin-inducible transgenic carrot promoter and have pleiotropic effects on morphogenesis.

Plant growth and development is regulated by complex interactions among different hormonal, developmental and environmental signalling pathways. Isolation of mutants in these processes is a powerful approach to dissect unknown mechanisms in regulatory networks. The plant hormones abscisic acid (ABA) and auxin are involved in vegetative, developmental and environmental growth responses, including cell division and elongation, vascular tissue differentiation and stress adaptation.