Differential expression of cell-wall-related genes during the formation of tracheary elements in the Zinnia mesophyll cell system

Plants, animals and some fungi undergo processes of cell specialization such that specific groups of cells are adapted to carry out particular functions. One of the more remarkable examples of cellular development in higher plants is the formation of water-conducting cells that are capable of supporting a column of water from the roots to tens of metres in the air for some trees. The Zinnia mesophyll cell system is a remarkable tool with which to study this entire developmental pathway in vitro. We have recently applied an RNA fingerprinting technology, to allow the detection of DNA fragments derived from RNA using cDNA synthesis and subsequent PCR-amplified fragment length polymorphisms (cDNA-AFLP), to systematically characterize hundreds of the genes involved in the process of tracheary element formation. Building hoops of secondary wall material is the key structural event in forming functional tracheary elements and we have identified over 50 partial sequences related to cell walls out of 600 differentially expressed cDNA fragments. The Zinnia system is an engine of gene discovery which is allowing us to identify and characterize candidate genes involved in cell wall biosynthesis and assembly.     

Approaches to understanding the functional architecture of the plant cell wall.

Cell wall polysaccharides are some of the most complex biopolymers known, and yet their functions remain largely mysterious. Advances in imaging methods permit direct visualisation of the molecular architecture of cell walls and the modifications that occur to polymers during growth and development. To address the structural and functional relationships of individual cell wall components, we need to better characterise a broad range of structural and architectural alterations in cell walls, appearing as a consequence of developmental regulation, environmental adaptation or genetic modification. We have developed a rapid method to screen large numbers of plants for a broad range of cell wall phenotypes using Fourier transform infrared microspectroscopy and Principal Component Analysis. We are using model systems to uncover the genes that encode some of the cell-wall-related biosynthetic and hydrolytic enzymes, and structural proteins.     

Patterns of protein synthesis in the moderately halophilic bacterium Deleya halophila in response to sudden changes in external salinity

Abstract Exposure of the moderately halophilic bacterium, Deleya halophila , to high NaCl concentrations (2 or 2.5 M) resulted in a transient cessation of cell division. The time taken for the cells to adapt and grow depended on the final salt concentrations. During the initial phases of adaption to high salt both the rate of protein synthesis and amino acid uptake were transiently inhibited. The extent and duration of the inhibition was dependent on the magnitude of the salt shock. Alterations in the patterns of pulse-labelled proteins were observed during adaption to high salt. The response of Deleya halophila cells to decreasing salinity (2.5 to 1 M NaCl) was also characterized by distinct changes in the protein profiles, whereas minor changes in the protein patterns were observed during adaptation from 1 M to 0.5 M NaCl. The labelled protein patterns of cells grown in 1 M or 2.5 M NaCl appear to be similar but not identical.