Physiological Effects On And Cloning Of LHCSR Gene From Ulva Pertusa Under Emersed Stress

U. pertusa habitats in the intertidal zone and be often exposed to an emersion state. Studies on physiological and biochemical changes as well as the regulation at molecular level of U. pertusa under stress will be very helpful to understand the adapting mechanism of the seaweed to the emersion stress. Among many proteins involved in the stress resistance, the light-harvesting complex stress-related (LHCSR) protein is present in the thylakoid membrane as a transmembrane protein, and combines with different light-harvesting pigments to absorb and transfer light energy to the photosynthetic reaction center. The LHCSR protein is likely to play an important role in photo protection, and synthesizes quickly under different environmental stress such as high irradiation, low temperature, emersed stress to ensure photosynthesis works normally by dissipating excess energy.In this study, the physiological responses of U. pertusa under artificially emersed stress were examined. The contents of Chla, MDA, soluble sugar, and free proline as well as the activity of POD in treated U. pertusa sampled from the intertidal zone at Dalian were measured after different emersed treatment times(0h、0.5h、1h、2h、4h and6h). The results showed that the content of Chla decreased slightly and in contrast, the contents of MDA and soluble sugars increased with the prolonging treatment time of emersed stress. Meanwhile, the activity of POD and content of proline increased obviously while treated longer time.The full length cDNA of LHCSR gene is cloned from U. pertusa by RT-PCR and RACE. The cDNA is1094bp in full length with a636bp ORF which encode a deduced211amino acid residues. The length of the5’UTR and3’UTR are77bp and380bp respectively. In different emersed stress times, the relative mRNA expression level of LHCSR gene was measured by fluorescence quantitative real-time PCR. The results showed that the expression level of LHCSR was the highest at0.5h after exposure to emersed stress, but the expression of the LHCSR gene decreased with the treatment time. All of the results provided some valuable references for the physiological studies of the intertidal algae and provided some theoretical basis for further revealing of the mechanism and expression pattern of the genes in U. pertusa under emersed condition.