Gel electrophoresis-based plant proteomics: Past, present, and future. Happy 10th anniversary Journal of Proteomics!

In this century we have assisted at an unimaginable expansion of proteomics, with continuous innovations and optimizations in methods, techniques, protocols, equipment, and associated bioinformatics tools. We have moved forward very fast from first (gel electrophoresis based), to second (based on isotopic or isobaric labelling), to third (shotgun or gel-free, label-free), and to fourth (targeted, mass-western, or SRM/MRM) generation techniques. This evolution is clearly observed in the literature since 1994, when the term "proteome" was first coined, with plant proteomics progressing at a much lower speed than human and other model organisms. The question behind this review is: Is gel electrophoresis an obsolete technique? Is it still alive? The answer is that gel electrophoresis is still a valid technique, with its own particularities, strengths, and weaknesses, "irreplaceable" in top-down experiments directed at investigating protein species, loci and allelic variants, and isoforms, as well as in the post-translational modifications and interactions studies; it is an excellent complementary and alternative approach that could lead us to achieve a deeper visualization and knowledge of the cell proteome. The past, present, and future of this technique is being reviewed. It is not pretended to discuss in detail technical aspects, referring to key original papers or previous reviews, but instead, how it has contributed, from a historical perspective, to plant proteomics and biology research. It is our personal congratulations to "Journal of Proteomics" that celebrates this year its 10th anniversary, and, at the same time, a tribute to those scientists who have contributed to the establishment and development of the gel electrophoresis technique and its application to proteomics and plant biology research. Their direct or indirect teaching has been very valuable to those of us who once decided to enter proteomics, with no access to any sophisticated and expensive equipment. This gel electrophoresis-based plant proteomics review is divided into the following sections: introduction, history, methodology, contribution to plant biology research, and future directions.