Effects of Three Exogenous Selenium on Rice Morphology, Photosynthesis, Antioxidant Enzyme System, and Identification of Selenium-Related Genes

Selenium (Se) is an essential trace element that has various beneficial effects for human healthy. However, the effects of different selenium sources, treatment methods and concentrations on growth and development, photosynthetic characteristics and antioxidant capacity are still unclear in rice. In this study, three concentrations of three different selenium sources were performed in rice using two treatment methods, respectively. The results showed that selenium treatment can increase the plant height of rice, decrease the kernels per spike. All the selenium treatments improved the photosynthetic indexes including net photosynthetic rate, transpiration rate, and stomatal conductance, decreased inter-cellular CO2 concentration. The activities of catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), and glutathione reductase (GR), as well as the content of GSSG (Glutathione oxidized) were increased at different levels after Se treatments, while GSH (Glutathione) decreased. Totally, 32 DEGs related to selenium absorption/endocytosis (including six heat shock 70 kDa protein, one ACD), transport (including four ABC transporters, one SULTR, one LAST, one Inorganic phosphate transporter, one GlpT, one PHO, one PPT) and metabolism (including NAS1, NAS2, APS5, 3MST2, PPCS1, SAMDC and 8 protein kinases), 6 DEGs related to glutathione metabolic pathway (including one G6PD, four GSTs and one GSS), 69 transcription factors (including 19 AP2/ERF-ERFs, 9 MYBs, 9 WRKYs, 8 HSFs, 6 bHLHs, 5 GRASs, 4 NACs,3 B3-ARFs, 3 C2H2s and 3 bZIPs) were identified by RNA-Seq. Our study indicated that exogenous selenium treatments could increase the plant height by improving photosynthetic traits and antioxidant enzyme activities, especially sodium selenite. The expressions of the genes related to selenium metabolism indicated that foliar spraying can faster induce the response of Se treatment in rice than root irrigation. The results will provide an insight into the selenium enrichment of rice.