figure a

Georgio Bernardi

figure b

Noboru Sueoka

At different points during the last year, two great molecular evolutionary biologists passed away: Giorgio Bernardi and Noboru Sueoka. And both made several crucial contributions to the field of molecular evolution in this journal.

Let me begin with Giorgio, who postulated the existence of isochores (for an old review, see Bernardi et al. 1985). Isochores were postulated as long regions (> 300 kb, internally rather homogeneous concerning GC content) that are interspersed in mammalian genomes.

Writing this reflection is not easy for me. Giorgio was my PhD advisor when he was in Paris at the Institut Jacques Monod. And, after learning science with him, we became friends. We continued to collaborate until last (and his final) year. He came to Uruguay several times. Generously, he received several students from Uruguay in his lab (first in Paris, then at the Stazione Zoologica Anton Dohrn, in Naples). The existence of something like evolutionary genomics in Uruguay is thanks to him. But not only people from our country were welcomed in his lab. His international group included people from Morocco, Algeria, Belgium, Italy, Russia, Germany, Switzerland and several other countries. And I remember the discussions we had. Discussing in a mix of English, Italian, Spanish, and French, his lab was, by definition, an international one. He was, of course, the boss, but always with an open mind. And it was great, for us all, to go to dinner with him. We always began discussions with isochores but, after some glasses of wine, we nearly always finished listening to his stories about his life and the origins of molecular biology, and about his friendship with people like James Watson, Jacques Monod, François Jacob, Motoo Kimura, Werner Arber and many others. A dinner with him was a lesson in the history of molecular genetics.

And the Journal of Molecular Evolution was a core part of this. He was Editor-in-Chief, together with Takashi Gojobori and Martin Kreitman during several years at the turn of this century. And he published several important (and polemical) papers in the journal. Among them, I choose just four: (1) Bernardi and Bernardi (1985), where he showed for the first time the correlations that hold between genomic GC and codon usage; (2) Bernardi and Bernardi (1986), where he postulated the effect of temperature for the appearance of GC-rich isochores in vertebrates and the crucial roles of non- coding sequences. (3) D’Onofrio et al. (1991), where he put together his idea of the isochore structure of the human genome with codon and amino acid usage. (4) Sabeur et al. (1993), where he showed the compositional distribution of isochores among several eutherian orders. Although not as important as those mentioned, I had the honor of publishing with Giorgio two papers in the journal: Musto et al. (1999a, b).

Last, but not least, he loved to organize courses and meetings. In these instances he liked to get selectionists and neutralists together, and I’m sure what he enjoyed the most were the long discussions, which beyond the meetings, lasted over dinner and afterward, sometimes drinking a good Italian wine (although some of us preferred the Scotch whisky).

And what can I say about the great Noboru Sueoka? I met him several times while I was working on my PhD thesis in Paris. Of course, the first time we talked, I knew about his crucial contributions to the field of molecular evolution (see, for instance, Sueoka 1962, 1988; Quinn and Sueoka 1970). And he was against Giorgio’s ideas. Indeed, while Giorgio was a selectionist, Noboru was in the opposite camp: he was a neutralist. And as a student, I had my doubts.

So, after his talk in Giorgio’s lab, I was a bit afraid of discussing ideas with such a great “man of science”. But to my surprise, he was kind and gentle. When I asked him to talk about his ideas, I addressed him, “Professor, may I talk with you?” And then, he asked my name and said, “Héctor, please call me Noboru and not Professor… and let’s have a cup of coffee and talk”. Of course, with that first talk I learned a lot. And we met two or three times after that day. And he remembered me (“you are the Giorgio’s student from South America, aren’t you?”). And perhaps, the most important lesson he gave me was “always think with your head”, meaning to always think carefully and precisely about science, and not simply follow the mainstream trends. What a lesson!

He made several crucial contributions. Among them, in my very personal opinion, the most important were the variation of GC content among prokaryotes; its relation with the genetic code (at a time were the distribution of codons for the 20 amino acids was not yet elucidated); the idea of the bidirectional replication of bacterial genomes; the concept of mutational biases, which states that the GC content is the result of biases intrinsic to the replication/repair systems acting on the genomic DNA. These results and ideas were all crucial contributions to the field of molecular evolution. His papers are still highly cited, and perhaps that is the highest contribution we can make to his life and seminal ideas. In my opinion, he was one of the founding fathers that made molecular evolution a new self-standing branch of scientific research. He passed away. But his ideas will remain. And I am very proud that several times I talked with and learned from the great Noboru Sueoka.

He published several papers in the J Mol Evol. Among them, I must quote (1) Sueoka (1992), where he postulates that the intragenomic heterogeneity of GC content of mammals and birds is mainly the result of the intragenomic differences of directional mutation pressure and selective constraints rather than the result of positive selection for functional advantages of the GC content itself; (2) Sueoka (1993), where he tackles the generally believed assumptions (at the time) in molecular evolution, such as a constant rate in evolution, the generality of higher mutation frequency for neutral sets of nucleotides, and others. (3) Sueoka (1995) where he discusses the deviations from the intrastrand parity rules and its relation to codon usage. Needless to say, these contributions were crucial for molecular evolution.

So, one year ago, almost at the same time, Giorgio Bernardi and Noboru Sueoka passed away. From the point of view of their respective ideas, they were on opposite sides. But personally, they respected each other. And the field of molecular evolution will miss both of them. Giants like them are what make science great. I pay them my deepest tribute.