McCurdy and Collings Lab

Cell and molecular biology of specialised plant cell walls

Our research focuses on understanding the mechanisms associated with building specialised cell wall structures in phloem parenchyma transfer cells in Arabidopsis, and phi thickening-containing cells of Brassica roots.

Transfer cells in Arabidopsis (McCurdy and Collings)

Transfer cells (TCs) build highly polarised cell wall ingrowths which serve to amplify plasma membrane surface area and hence maximise the nutrient transport capacity of these cells. Apart from their important role in enhancing nutrient transport in plants, and thus influencing crop yield, the deposition of highly polarized wall ingrowths represents a fascinating example of localised wall deposition in plant cells. Our current research on TCs uses the model species Arabidopsis thaliana (Arabidopsis): the enormous genetic and bioinformatics resources available in this species allow us to investigate the molecular regulation of cellular processes leading to TC development. In Arabidopsis, phloem parenchyma (PP) cells in vascular tissue of leaves and leaf-like organs develop wall ingrowths to become PP TCs, performing an important role in phloem loading of photoassimilates into cells of the sieve element/companion cell complex for export to developing tissues and organs. Using a novel fluorescence staining procedure in combination with confocal and super-resolution microscopy, we have mapped PP TC development across cotyledon and leaf development and used this information in combination with RNA-sequencing to identify members of the NAC and MYB gene families that likely participate in the control of PP TC development in Arabidopsis. Since PP TCs play important roles in loading of sugars into the vascular pipeline of source leaves for delivery to developing sink tissues, we are also investigating signals, especially sugars, which may be involved in directing the development of PP TCs.

A major advance in understanding phloem parenchyma transfer cell development in Arabidopsis is our recent discovery that this process represents a novel trait of vegetative phase change, or heteroblasty, in Arabidopsis. The genes and microRNAs that regulate vegetative phase change sit at the interface of vegetative and floral transition, thus providing new opportunities to discover regulatory networks controlling the development of PP TCs.

Phi thickenings in roots of the Brassicaceae (Collings and McCurdy)

Phi thickenings are thickened secondary cell wall bands that are formed around root cortical cells in locations where primary cell walls would normally only be expected. These phi thickenings have been identified in a range of species from gymnosperms to angiosperms, but their function within the root remains unknown. As phi thickenings are not known to occur in the model plant Arabidopsis thaliana, we have instead focussed our research into phi thickening development in the primary root of two agriculturally-important and closely related species, Brassica napus (canola, rapeseed) and Brassica oleracea (broccoli, cauliflower, cabbage and related cultivars). Our research has demonstrated that these phi thickening bands can be rapidly induced by water stress, and that there are wide variations in thickening induction in response to this water stress between different cultivars. Current research is focussed on confirming the functions of phi thickenings within the Brassica root, and identifying the cellular and molecular pathways through which these enigmatic structures develop.

Enquiries

Associate Professor David McCurdy

Associate Professor David Collings