Comparative effects on nutritional quality and selenium metabolism in two ecotypes of Brassica rapa exposed to selenite stress

The metalloid selenium (Se) is one of the important micronutrients for humans and plant growth. However, high Se concentrations in the soil is toxicity to normal plants. Therefore, research on Se metabolism in plants and its biological impacts on plant growth is very important. The vegetable Brassica rapa (B. rapa), known as a Brassicaceae Se accumulator, is a very important organic Se source for humans. In the present study, to investigate the Se metabolism in B. rapa under selenite (SeIV) stress, two species of B. rapa, B. rapa var. perviridis (Br. perv) and B. rapa var. purpuraria (Br. purp), have been selected as model plants. We grew the two B. rapa ecotypes in different Se(IV) concentrations and monitored biomass, physiological phenotypes, Se distribution and transport rates. The results reveal that low concentration Se(IV) can improve the nutritional quality of both B. rapa species, but Se can more significantly affect the biomass of Br. purp than Br. perv. And the Se content in Br. purp was up to 2 times higher than in Br. perv. Furthermore, expression levels of genes from Se metabolism-related gene families, such as APS, APR, SAT, SMT, CysD and MMT, were analyzed using qRT-PCR assays. The qRT-PCR results show that Br. purp was more tolerant to Se(IV) treatment than Br. perv. The present study is very important for further characterize the Se uptake and translocation metabolism in different ecotypes of B. rapa.