The proteomics of senescence in leaves of white clover, Trifolium repens (L.)

Abstract

A proteomics approach has been used to study changes in protein abundance during leaf senescence in white clover. Changes in cell ultrastructure were also examined using transmission electron microscopy. The most obvious ultrastructural changes during senescence occurred in chloroplasts, with progressive loss of thylakoid integrity and accumulation of osmiophilic globules in the stroma. Quantitative analysis of 590 leaf protein spots separated by two-dimensional electrophoresis indicated that approximately 40% of the spots showed significant senescence related changes in abundance. Approximately one-third of the protein spots present in mature green leaves were also visible by two-dimensional electrophoresis of an isolated chloroplast fraction, and these spots represented a major proportion of the proteins showing senescence related declines in abundance. Chloroplast proteins that were identified by matrix-assisted laser desorption/ionization-time of flight mass fingerprinting included rubisco large and small subunits, a rubisco activase and the 33 kDa protein of the photosystem II oxygen-evolving complex. These proteins declined in abundance late in senescence, indicating that the photosynthetic apparatus was being degraded. A chloroplast glutamine synthetase showed partial decline in abundance during late senescence but was maintained at levels that may support provision of glutamine for export to other tissues. The results emphasise the importance of proteolysis, chloroplast degradation and remobilisation of nitrogen in leaf senescence.

Separation and identification of soybean leaf proteins by two-dimensional gel electrophoresis and mass spectrometry

“…1. The dynamic range of protein accumulation is very large; this is a problem for leaf proteomic analysis because the preponderance of ribulose bisphosphate carboxylase/oxygenase (Rubisco) masks the detection of other proteins (Wilson et al, 2002;Watson et al, 2003). However, in our system a significant number of proteins were clearly separated and identified despite the predominance of Rubisco in the central portion of the gels.…”

Proteome analysis of muscadine grape leaves

“…Leaves are the main organ of photosynthesis and transpiration in higher plants and therefore, a large number of proteome studies have been concerned with various aspects of leaf development, genetics, and exposure of plants to a wide range of biotic and abiotic stresses. [4][5][6][7][8] The progress made in the separation of proteins by two-dimensional gel electrophoresis (2-DE) coupled with the development of mass spectrometric technique has allowed powerful analysis of proteome changes and genetic differences. In most green leaf proteomes, ribulose bisphosphate decarboxylase/oxygenase is the most abundant protein, and can comprise more than half of the total leaf protein in some species.…”

Impact of solar Ultraviolet-B on the proteome in soybean lines differing in flavonoid contents

“…The 2-D PAGE gels were reproducible and had well-separated spots, although as is frequently observed with proteome analysis, the dynamic range of protein accumulation was very large (Wilson et al, 2002;Watson et al, 2003). A representative gel image is presented in Fig.…”