S05 - Session O6 - Evolution of scent genes in roses

Authors: Jean-Claude Caissard *, Corentin Conart, Nathanaelle Saclier, Fabrice Foucher, Clément Goubert, Aurélie Bony, Saretta Paramita, Sandrine Moja, Tatiana Thouroude, Christophe Douady, Pulu Sun, Baptiste Nairaud, Denis Saint-Marcoux, Muriel Bahut, Julien Jeauffre, Laurence Hibrand-Saint Oyant, Robert Schuurink, Jean-Louis Magnard, Benoit Boachon, Natalia Dudareva, Sylvie Baudino

Rosa is a complex taxon with more than 150 intertwined species. Only few have been domesticated by humans since Antiquity, reaching today more than 30,000 cultivars. One of the major traits that have been selected is scent. However, rose scent is a complex trait relying on dozens of odorant molecules. Some of these molecules originate from a specific and unique evolution of biosynthetic pathways in the genus Rosa , which arose from acquisition of new functions of genes involved in the production of scent compounds. Examples include the duplication of OOMT1 and 2 and the acquisition of the ability to synthesize 3,5-dimethoxytoluene (Scalliet et al. 2008). It is also the case for NUDX1 , a gene involved in geraniol biosynthesis specifically in roses (Magnard et al. 2015). Here we show that multiple trans - and cis -duplications of NUDX1 during the evolution of Rosaceae and Rosa , has led to the specialization of the paralog NUDX1-1a in geraniol production. This paralog is not present in the more ancient wild roses, which makes them unsuitable for crosses to obtain fragrant roses. Previously we showed that some cultivars derived from an hybrid of R. wichurana , have a different specialization: NUDX1-1a is not active, but NUDX1-2c , another paralog, is active and involved in E,E -farnesol production (Sun et al. 2020). Furthermore, some gene alleles may encode functional enzymes in vitro , but are not always expressed in planta . This is the case for LIS and PAAS genes, respectively involved in linalool and 2-phenylthanol biosynthesis (Magnard et al. 2018; Roccia et al. 2019). Taken together, these results indicate different evolutionary scenarios from one rose species to another. A deep knowledge of the genes and alleles involved in the odorant molecules is thus needed to help the selection of new cultivars of fragrant roses. Ref: Magnard et al. 2015, Science 349, 81-83; Magnard et al. 2018. Plant Physiol. Biochem. 127, 74-87; Roccia et al. 2019. Plant Physiol. 179, 1064-1079; Scalliet et al. 2008. PNAS 105, 5927-5932; Sun et al. 2020. Plant J. 104, 185-199.