I wish to thank Giorgio Bernardi for having so kindly invited me to take part in what will be, undoubtedly, a fascinating colloquium devoted to Biological Sciences at the turn of the century. 1 am also very pleased to be back, after many years, at the Zoological Station in Naples. Firstly because this gives me the great pleasure to meet so many friends, including himself but also because it reminds me with emotion, of the first time I met Professor Alberto Monroy and of our first discussions about messenger RNA in amphibians. As national representative of ICSU, it also gives me the opportunity to greet my colleagues and friends from IUBS, since the colloquium and the general assembly will go side by side.

When I began my activity as a biologist, in 1947, nucleic acid metabolism held only peripheral interest. People, at that time, were mostly concerned with the glycolytic pathway, the Krebs cycle, the mechanisms of enzyme action, hydrogen transport and the role of vitamin and lipids in animal nutrition! Genes, of course, were known, but, in spite of the early publications on the "transforming principle" by Avery at the Rockefeller Institute, they were still looking like a "black-box," as far as their physicochemical nature, their mode of replication and even their precise function in the cell economy were concerned. The biology of the gene was far less advanced than was the physiology of the entire organism, or the biology of the cell. The "big turn", as everyone knows, was the discovery of the double helix (Table 1) that constituted the first stage of the molecular biology "saga," with its main consequences: the genetic code, the mechanisms of RNA and protein synthesis, the messenger RNA discovery, the central dogma hypothesis, etc... The first table emphasizes some of the very early achievements illustrating major landmarks in biochemistry, and molecular biology preceding the onset of DNA technology: one such milestone was the demonstration that nucleic acid-like polymers could be made in vitro, followed by the discovery of DNA-dependent RNA polymerase. 1961 marked the first identification of mRNA in phages and bacteria, lending support to the central dogma hypothesis. Then came the discovery of the reverse transcriptase and of the restriction enzymes, as biological weapons preparing the advent of genetic engineering. While these first achievements were based upon prokaryotic models, the switch of molecular genetics to eukaryotic systems was made possible by the onset of Recombinant DNA technology and by the accompanying development of cDNA cloning (Table 2).

The first success in achieving cDNA cloning was due to work by Mach, Kourilsky and Rougeon (in Geneva and at the Pasteur Institute). This encouraged people to make use of this approach to isolate and purify many eukaryotic genes playing an important role in the economy of the eucaryotic life. Yet, 20 years ago, no one could predict the explosive impact of molecular and developmental genetics and the fact that gene-based technologies would become so instrumental in all the areas of life sciences, including: immunology, neurobiology, general physiology, pathophysiology, development and up to the study of biodiversity and the origin of life (Table 3).

Table 1 : The "Prehistoric Period" - From Polynucleotide Synthesis to the Onset of Genetic Engineering

Table 2 : c-DNA Cloning

Table 3 : The Genetic Paradigm and its Impact on Life Sciences

Some of the main clues explaining this phenomenon of irrigation of life sciences by molecular genetics relate to methodological breakthroughs, such as gene cloning, transgenesis, comparative sequence studies involving gene banks, reverse genetics, pharmacogenomics, utilization of micro-arrays, etc. Others are of a more fundamental nature such as: the deciphering of positive control mechanisms, the discovery of developmental genes, of transduction cascades and of apoptotic mechanisms....

But, at this stage of my remarks, I would not like to leave the audience with the feeling that molecular and genetic approaches are "self sufficient" for a thorough and global understanding of life. This way of thinking would give rise to a somewhat naive and oversimplified vision about the present status of life sciences...

Understanding the structure of molecules, gene action and regulatory circuits is fine, but many more efforts are needed if we want to understand functions and really penetrate inside of the complex hierarchy in the organisation and physiology of living beings or the way they interact with the environment.

On the one hand, it seems to me that some aspects of biology will probably reflect a more reductionistic attitude as a result of the most recent achievements in physics and informatics; on the other, biology of the 21st century will also pursue a complementary, if not opposite direction, not only to integrate molecular data into complex physiological systems, but also to tackle directly the complex systems themselves. Table 4 emphasizes some of the present challenges that "structural biology" has to face; that is to say, to better understand the physico-chemical phenomena of life both in time and space.

For example, the recent data concerning the 30S ribosome structure, derived through a combination of synchroton radiation and computerized models, has completely renewed our concepts about the function of these organelles in protein synthesis by showing that this ribosomal RNA, rather than ribosomal proteins, is playing a major role during the main translational steps. Also, great progress has been made in the microscopic examination of the cell, thanks to the new performances of multiphotonic microscopy, which provides access to protein traffic within the cell.

Table 4 : A New Reductionistic Approach Using Highly Resolving Power Techniques combined with Model Driven Acquisition

• Applications to the analysis of cellular superstructures
  (chromosomes, membranes, ribosomes, cytoskeleton)
  
  • ultra rapid transconformations
  • use of synchroton radiations for crystallographic studies
  • improved visualization of cellular components using new microscopes (biphotonic, tunnel effect ... )
    
    
• Refine the clues for studying the 3-D structures of proteins

Much more work will be needed to understand genome organisation within such superstructures as chromatin or the nucleus, and we still know relatively little about the mechanisms of tridimensional protein folding, as well as the rules involved. Too few protein structures have thus been described, and there is no clear-cut relationship between their primary sequences and their 3D structure.

Now, turning towards higher levels in the organisation of the living beings, it is clear that we will have to face even more difficult challenges (Table 5). Not only shall we have to store and handle a fantastic amount of gene sequence data and to compute gene expression profiles in order to arrive at integrated physiological functions (and hence to reach the complexity of what Zuckerkandl is defining as "Regulomics,") but it looks obvious to many people that there is urgent need for a complete revival of taxonomy and for the analysis of functional biodiversity.

Finally, neurosciences constitute a world in itself that not only embraces molecular genetics but bears upon many complex phenomena related to the communication between neurons, to the state of consciousness and touching the various aspects of cognitive sciences including psychology. According to Gunther Stent "…Consciousness remains one of the last unsolved great biological problems."

Table 5 : From Molecules to the Biosphere ....

• An unprecedented effort will be needed (in Bioinformatics...) to integrate data from gene sequence analyses, as well as transcriptome and proteome studies, into a physiologically coherent picture, to learn more about functions
  
  
• "Regulomics" after "Genomics"
  
  
• Bioinformatics should be in synergy with systematics to better tackle biodiversity (the taxonomic and functional diversity of living organisms)
  
  
• But this should not obviate the need for more traditional methods (field exploration; management of large collections and specimens)
  
  
• The goal is to attempt a catalogue of life on earth...

In conclusion, and as is so clearly stated by IUBS and more specifically by Marvalee Wake in the paper that she will be presenting in a forthcoming session; "Many of the questions now being addressed by biologists require both reductionistic and incorporative elements, but in a framework that allows the resolution of the sub-elements of the question to contribute to an answer to a larger problem..."

Even if there exist different connotations for the word "integrative biology," which, as Dr. Wake will explain, is more than the pure aggregation of workers with different expertises to consider complex problems, I am convinced that the majority of people present in this room share the view that the 21st century will be the century of "integrative biologists," that is to say, of "…biologists trained in such a way as to span different levels of biological organisations, of the complex hierarchy of the living world, and perhaps extend to non-biological realms."

François Gros
Académie des Sciences, Paris