Expression And Regulation Of Maize Raffinose Synthase Gene

Maize,as an important food crop,is facing various abiotic stresses in its whole growth cycle.Raffinose is a functional tri-oligosaccharide specific to plants,its content in cells is closely related to plant resistance and seed activity.However,the molecular regulatory mechanism of RFOs synthesis remains unclear.This study has investigated the regulation of the ZmRAFS gene.The main results are shown as follows:(1)Raffinose synthase gene(ZmRAFS)is regulated by biological clock.ZmRAFS gene expression revealed that it is under circadian control and this expression pattern was highly conserved in different maize lines.Raffinose content in leaf is also correlated with circadian rhythms.(2)The ZmPRR suppressors,the core element of the biological clock,inhibit the expression of ZmRAFS gene via the G-Box element.ZmPRR or GFP expression vector was constructed and were co-transferred into maize protoplast with the reporter vector in which Rluc was driven by the ZmRAFS gene promoter.The experimental results showed that Rluc expression was inhibited by PRR protein,and this inhibition was mediated by the G-Box cis-acting element in the ZmRAFS gene promoter.(3)ZmHB7 and ZmPRR have antagonistic effects on the regulation of ZmRAFS gene under drought stress.Stress treatment experiments showed that ZmRAFS gene ZmRAFS gene was regulated by biological clock and induced by drought and ABA stress.ZmHB7 transcription factor was also up-regulated by dehydration and ABA treatments.Protoplast experiments showed that ZmHB7 positively regulates ZmRAFS expression.Further investigation showed that ZmHB7 and ZmPRR inhibitors antagonistically regulate the ZmRAFS gene expression.In summary,this study provides a molecular basis of ZmRAFS gene expression regulation in response to abiotic stresses.