Chlorophyll-a fluorescence evaluation of PEG-induced osmotic stress on PSII activity in Arabidopsis plants expressing SIP1

In this study, we evaluated the effect of osmotic stress on photosynthetic machinery of Arabidopsis plants expressing a gene encoding small basic intrinsic protein (SIP1) isolated from Solanum tuberosum. Intact leaves of SIP Arabidopsis plants were exposed to 15% polyethylene glycol (PEG) solution and fast Chlorophyll-a (Chl-a) fluorescence induction kinetics was measured. Photosynthetic parameters like ratio of variable and maximum fluorescence (F_V/F_M), absorbance of photons per active reaction center (ABS/RC), trapping of photons per active reaction center (TRo/RC), electron transport per active reaction center (ETo/RC), and performance index (PI) were measured. Furthermore, the energy pipeline model was deduced in response to PEG stress. The membrane model includes a visualization of the average “antenna size”, which follows the value of the ABS/RC. Analysis of SIP Arabidopsis plants under PEG stress through fast Chl-a fluorescence transient showed that the damage caused due to PEG is more prominent at the donor side rather than the acceptor side of PSII. Higher PI in SIP plants under PEG stress indicated a better vitality than control plants. Overall, these results indicate that constitutive expression of SIP1 in Arabidopsis plants induces significant changes in the photosynthetic machinery under PEG-induced osmotic stress.