Cloning and analysis of the sequences of the super-selenium-rich plant Cardamine hupingshanensis

We employed a pair of universal primers for PCR amplification of Cardamine hupingshanensis leaf DNA collected from the soil of a unique selenium-rich deposit in Yutangba, Enshi, China. Then the PCR products were sequenced to obtain the 852-bp DNA sequences containing internal transcribed spacers (ITS). The ITS DNA sequences of different Cardamine species were aligned and spliced to obtain a “reference” sequence. Next, the base differences were compared between the ITS sequences of different Cardamine species and the “reference” sequence. Our results showed that Cardamine hupingshanensis had the greatest differences (17) compared with the “reference” sequence, much more than those between the ITS sequences of other Cardamine species and the “reference” sequence and 3.2 times higher than the average. It is speculated that some Cardamine species growing in selenium-rich regions of Enshi for a long time produce genetic variations that can adapt to high selenium soil stress and develop a super selenium enrichment capacity, thus evolving the new species Cardamine hupingshanensis. Therefore, we proposed the hypothesis of accelerated evolution of Cardamine hupingshanensis under high selenium soil stress.