Format: ORAL

Jeroen van der Woude1, Maggie-Anne Harvey1,2 and Antony van der Ent1,2,3

1 Laboratory of Genetics, Wageningen University and Research, Wageningen, The Netherlands, 2 Centre for Mined Land Rehabilitation, Sustainable Minerals Institute, The University of Queensland, Brisbane, Queensland, Australia, 3 Université de Lorraine, INRAE, LSE, F-54000 Nancy, France

Selenium (Se) is formed in supernovae and is a rare component in most soils. Nevertheless, many organisms including Homo sapiens need selenium to produce selenocysteine (SeCys), also referred to as the 21st amino acid, required for synthesis of so-called selenoproteins. In contrast, land-plants lost the need for selenium, likely due to a decreased bioavailability of Se over the last couple of million years. Interestingly, some plants have developed a selenophile lifestyle regardless, growing on selenium-rich soil toxic to most plants. Some of these plants such as Neptunia amplexicaulis hyperaccumulate selenium up to 1.3% of their dry mass. These high tissue Se levels normally cause severe oxidative stress and dysfunctional proteins due to inadvertent incorporation of SeCys en lieu of cysteine. The latter is caused by the chemical similarity of selenium to sulfur, leading to the production of various organic selenium compounds through the sulfur transport- and assimilation pathway, including SeCys and Selenomethionine. However, in the dry and saline Australian outback, Neptunia amplexicaulis manages to grow well on toxic soil and accumulate extreme concentrations of selenium in the plant tissue. Its sister-species Neptunia heliophile has also developed an increased tolerance to selenium, but rather excludes Se from its tissue instead of accumulating it. Our work aims to determine what mechanisms are necessary for the extreme lifestyles of N. amplexicaulis and N. heliophila and especially how to accumulate and tolerate high tissue selenium levels. This investigation involves the analysis of recently sequenced genomes of N. amplexicaulis and N. gracilis as well as full-length transcriptomics. Furthermore, this work involves the development of transformation protocols for N. amplexicaulis to get direct evidence of gene involvement in Se hyperaccumulation. The research outcomes could help improve crop Se content and thereby ameliorate the currently widespread Se-deficiency in various human populations.