Cloning And Functional Characterization Of SePSY And SeLCY From Salicornia Europaea L.

Salicornia europaea L. is a succulent and leafless euhalophyte with no salt glands or bladders, which remains alive in 1020 mM NaCl. It is a good germplasm resource for salt tolerance for its special morphological traits. Up to now, there have been only a few reports on the salt tolerance involved in physiological and molecular mechanism in S. europaea. The present study focused on the effects of salt and osmotic stresses on ion homeostasis and photosynthesis of S. europaea. Then two cDNA ecoding phytone synthase (SePSY) and lycopeneβ-cyclase (SeLCY), which were the key enzymes in the carotenoids biosynthesis pathway were cloned from S. europaea and functionally characterized. This work was important for the understanding of the role that carotenoids played in plant salt tolerance.The results showed that 200 mM NaCl was the optimal NaCl concentration for the growth of S. europaea. The photosynthetic efficiency of the plant was increased under NaCl of 200 mM, as was evidenced by the increased ratio of chlorophyll a/b and the value of light saturation point. However, PEG-6000 of 27%, which has the same osmotic pressure as that of 200 mM NaCl, resulted in an opposite effect. When treated with 200 mM NaCl, the level of Na~+ of seedling was significantly higher than that without salt treatment, however, the content of proline had no significant change whether with or without salt treatment. It indicated that Na+ was more important in regulating ion homeostasis than proline. NaCl of 200 mM specifically induced the activity of V-H+-ATPase compared with the control. The expression of SeNHX1 is constitutive both under NaCl and PEG treatments. We concluded that the increased...