Dr. Morgante will give a keynote address on Monday, August 25, for the Arborea-Treenomix Conifer Genomics Workshop. 

 

THE ANALYSIS OF GYMNOSPERM GENOMES: IS THEIR STRUCTURE AND HISTORY MAKING THEM EASIER TO SEQUENCE?

 

Michele Morgante*,**, Emanuele De Paoli**

*) Istituto di Genomica Applicata, Via Linussio 51, 33100 Udine, Italy; **) Dipartimento di Scienze Agrarie e Ambientali, Università di Udine, Via delle Scienze 208, 33100 Udine, Italy

 

The emerging model for genome evolution in flowering plants proposes that i) the main factor underlying the increase of genome size is represented by the mobilization of a few families of LTR-retrotransposons that tend to be species-specific; ii) most detectable LTR-retrotransposons appear to have inserted within the last 0-4 million years while older elements cannot be fully detected due to progressive rearrangements that made them unavailable for dating; iii) repetitive DNA, particularly LTR-retrotransposons, undergo a relatively rapid turnover due to specific processes of DNA removal. With this model in mind we approached the analysis of two gymnosperm genomes, Norway spruce and Ginkgo respectively, to investigate the age and distribution of their repetitive components with particular emphasis on the features of LTR-retrotransposons. Surprisingly, our data revealed that gymnosperm genomes do not fulfil the angiosperm model and rather showed that the increase of genome size was caused by the proliferation of several but non-abundant retrotransposon families, whose insertions, in spruce, can be dated back to more than 100 million years ago. On the contrary, Ginkgo, which is regarded as a botanic fossil, may have experienced a more recent burst of retrotransposon mobilization. The slow mutation rate of gymnosperms was not sufficient to explain the extraordinary degree of sequence conservation between repetitive elements that mobilized in the same time span in both Ginkgo and conifers at least hundred million years after their divergence. We propose a model for gymnosperm genome evolution that combines the low mutation rate with a slow but steady retroelement proliferation and a low rate of DNA removal.

We will discuss the implications of these findings for the possible strategies for sequencing conifer genomes by considering both traditional as well as new sequencing technologies.

 

Michele Morgante is currently the Scientific Director of Istituto di Genomica Applicata in Udine and is full professor of Genetics at the University of Udine. He was educated as a geneticist in Padova and Udine and then worked for 5 years at DuPont Crop Genomics as Senior Scientist. His research group has been instrumental in establishing a number of genetic technology platforms that are now being widely deployed in plant genomic research (e.g. microsatellites, fluorescent BAC fingerprinting). His research programme is currently focusing on genome analysis in plants, including physical mapping, genome sequencing and resequencing and genome evolution studies, and on sequence diversity analysis and association mapping. He has contributed to the sequencing of the grapevine genome. He is particularly interested in novel approaches to dissecting complex traits and in developing the genomics and informatics technologies needed for this. Lately he has become interested in understanding the role of junk DNA in determining phenotypic variation.

He is a member of Accademia Nazionale dei Lincei and has received the 2005 Medal for Physical and Natural Sciences of the Accademia Nazionale delle Scienze detta dei XL. He is an Associate Editor of Theoretical and Applied Genetics and Tree Genetics and Genomes.