Promotion of growth and upregulation of thylakoid membrane proteins in the halophyte Salicornia bigelovii Torr. under saline conditions

Salicornia bigelovii is an unusually salt-tolerant plant species and is able to continue to photosynthesize and grow in saline conditions. There is an interest in understanding the mechanisms of this salt tolerance. In this study, S. bigelovii plants grown under 400 mM NaCl had higher growth and higher photosynthetic capacity than those not grown with salt. The intensities of the fluorescence emission peaks in the thylakoid membrane spectra in the salt treatment were higher than in the control. PSII and PSI peaks of the control were blue-shifted, indicating that salt deficiency affects energy transfer and structural stability in PSII and PSI. Both SDS-PAGE and western blot illustrated that the PSI proteins PsaA and PsaB and the PSII proteins CP47 and CP43 were upregulated with salt treatment, which might partly explain the change in the energy transfer process. Furthermore, Lhcb1 was also stimulated by salt treatment while Lhcb2 and Lhcb3 did not show noticeable changes. This demonstrated that salt is important in the maintenance of photosynthesis. In summary, treatment with salt led to an increased amount of PsaA/B, CP47, CP43, and Lhcb1 with a concurrent increase in antennae size. These photosystem changes may be responsible for the adaptation of S. bigelovii to saline conditions.