Although proteomists working with gel-free methods are considering the gels as 
coming from the past, proteomics based on gels has still a lot of opportunities 
to offer and acquisition of images on which thousands of spots may be resolved 
is still largely performed. Nowadays, two-dimensional electrophoresis remains a 
powerful tool to explore the plant proteome and to unravel changes in protein 
abundance between samples. Some weak points can be pointed out, as for any 
method, as for example the lack of reproducibility, or the detection of 
low-abundance proteins. The use of the technique called "difference gel 
electrophoresis" or "DIGE" can help to overcome or at least to reduce these 
inconveniences. DIGE requires the labelling of proteins by fluorochromes prior 
to their separation on 2DE gels. This technique may be applied to a wide array 
of plant stress studies, among others to trees. Accurate quantitative results 
can then be obtained and proteins presenting an interest in the studied stress 
are subsequently subjected to an enzymatic digestion (usually with trypsin) and 
identified using electrospray ionization, matrix-assisted laser 
desorption/ionization-time-of-flight-MS, and/or tandem MS.