J. Nagaraju: a Mémoire

Dr. Pierre Couble

Dr. Pierre Couble

Dr. Couble, renowned molecular biologist and silkworm biologist was a close associate and friend of the late Dr. J. Nagaraju. Dr. Couble, in spite of his busy scientific engagements, has found time to write a reminiscence on his departed friend. We at 'THE SILKWORM' are honoured in publishing this reminiscence.

Dr. Pierre Couble is currently The CNRS Research Director, CNRS-Université Lyon, France. Contact him at: Pierre.Couble@univ-lyon1.fr

Dr J. Nagaraju passed away on the 31st of December 2012. All those who knew him are devastated by his sudden death. Dr Nagaraju was a passionate, inspired and imaginative scientist and a beloved friend. He brought a vast contribution to silkworm biology, in many distinct areas. His curiosity was endless, with a permanent attention that scientific progress be useful to society.

Dr J. Nagaraju started his career at the Central Sericultural Research and Training Institute in Mysore (Karnataka), as a Central Silk Board (CSB) employee. In 1989, he came to Lyon (France) for a two-year stay at the CNRS to work on the cellular and molecular genetics of the silkworm. This is when we started to work in collaboration. Back to India, he was invested by the CSB with the mission of running Seribiotech, a brand new research laboratory in Bangalore in the fast emerging field of biotechnology, aiming at blending fundamental and applied research. After the Seribiotech experience, Dr Nagaraju moved to Hyderabad in 1998 and joined the Center for Cellular and Molecular Biology (CCMB) and the Centre for DNA Footprinting and Diagnostics (CDFD) where he settled down finally. In 1997, he stayed for one year at Harvard University in the laboratory of Daniel Hartl.

Dr. Pierre Couble and Dr. Nagaraju In Durban, summer 2008

Dr Nagaraju first developed fingerprinting of the Bombyx genome by various approaches to assess the genetic diversity of the silkworm in multiple ecotypes and inbred lines. With his little team at Seribiotech, he characterized the first B. mori microsatellites, their type, abundance and polymorphism, and their potential for traceability of genetic resources. He maintained interest in repetitive DNA throughout his career and more recently developed SilkSatDB, a silkworm microsatellite data base and then InSatDb, an interactive interface to query information regarding microsatellite characteristics of fully sequenced insect genomes.

As a major silk-producing country, India is home to the mulberry silkworm but also to three other varieties of natural silks: tasar, eri and muga, unique silkworm species that feeds on specific host plants. In this field, Nagaraju pioneered the study of the diversity and of the population structure of these rare silkmoths, of dwindling culture.

His experience in the study of genome polymorphism and plasticity led him to investigate the genetic diversity of Basmati rice, a high added value product of India agriculture. By using SSR markers, he could develop rapid multiplex microsatellite marker assays for the authentication of traditional Basmati varieties, which awarded him the gratefulness of the Indian government.

In CCMC and CDFD, he also took interest in many fundamental questions. One concerned determination of sex, a fascinating paradigm owing to the myriad of sex determining primary signals among insect species, which he approached with Giuseppe Saccone (Italy). He worked at deciphering the collection of the genes carried by the Z chromosomes (in silkworm males are ZZ and females ZW) and initiated a study of the female specific chromosome W that is strongly female determining and was long thought to harbor feminizing genes. Dr Nagaraju identified such a W-chromosome linked gene, a remarkable finding since that gene may be a master contributor of the female sex. He conducted such critical work in collaboration with Kasuei Mita, Toshiki Tamura and colleagues from Japan. Unfortunately, this masterpiece will be published after his death.

Recently, Dr Nagaraju’s group and we in Lyon constructed silkworm transgenic lines which added a genetic trait that confers refractoriness to infection by baculovirus, a major pathogen in Indian sericulture facilities. The beneficial trait was introgressed into a commercial race, allowing to combine high silk productivity and immunity to the virus. This first industrial application of transgenesis illustrates the will of Dr Nagaraju to exploit genetic concepts practically. Several important traits have not yet been handled successfully in traditional breeding schemes. Dr Nagaraju always pleaded for the incorporation of modern genetic analysis in selection, which coupled with conventional breeding, allows the dissection of complex, multi-gene controlled traits. In this respect, Dr Nagaraju was a restless go-between, linking the community of the basic scientists and that of the sericulture industry.

The sad passing away of Dr Nagaraju poses the question of his successor as a guide of Indian silkworm research programmes and as a recognized international spokesperson who always worked to connect science and society.