How do plant cells control their morphology? The role of ethylene signalling in the molecular control of cell shape

Background

Ethylene gas is a hormonal signal in plants, required for a range of developmental processes. One such process is the control of cell shape and elongation, linked to growth, mediated by the cytoskeleton network. Mutants with enhanced ethylene signalling or biosynthesis, such as the signalling mutant polaris or the biosynthesis mutant eto, or seedlings teated with the ethylene precursor ACC, exhibit a short root length. Wildtype seedlings grown in the dark are normally elongated, but when treated in the dark with ethylene or ACC develop a so-called triple response (short root, wide hypocotyl, exaggerated apical hook), and ethylene hypersignalling or biosynthetic ethylene overproducers exhibit the triple response phenotype in the absence of applied ethylene. Ethylene signalling also interacts with the hormone auxin, itself required for cell morphogenesis and division, and auxin is distributed in tissues by transport mechanisms (the PIN protein transporters) that in turn are influenced by ethylene.

A key question to be investigated in this project is how ethylene regulates cell shape via the auxin transport pathway, and the role of the cytoskeleton. Ethylene promotes polar auxin transport in roots by upregulating the PIN transporter proteins, which in turn are localized to the membrane through the cytoskeleton. How this interaction with the cytoskeleton is regulated is poorly understood, and will be investigated.

Experimental approach

1. Analysis of actin dynamics through fluorescence recovery after photobleaching (FRAP) analysis of the fluorescent actin marker FABD2:GFP, in the presence and absence of exogenous ethylene precursor ACC or the auxin IAA, or in the ethylene overproducing mutant eto, compared to wildtype.
2. Analysis of tubulin dynamics through FRAP analysis of the fluorescent actin marker FABD2:GFP, in the presence and absence of exogenous ethylene precursor ACC or the auxin IAA, or in the ethylene overproducing mutant eto, compared to wildtype.

1. Analysis of PIN protein dynamics through FRAP analysis of the fluorescent actin marker PIN1:GFP and PIN2:GFP at the plasmamembrane, in the presence and absence of exogenous ethylene precursor ACC or the auxin IAA, or in the ethylene overproducing mutant eto, compared to wildtype.

The project will provide the student with experience in plant genetics, molecular biology and advanced bioimaging.

For more information, please contact Professor Keith Lindsey.