Understanding the molecular mechanisms of environmental salinity stress tolerance and acclimation strategies by photosynthetic organisms facilitates accelerating the genetic improvement of tolerant economically important crops
Understanding the molecular mechanisms of environmental salinity stress tolerance and acclimation strategies by photosynthetic organisms facilitates accelerating the genetic improvement of tolerant economically important crops In this study we have chosen the marine algae Dunaliella D salina a high potential and unique organism that shows superior tolerance against abiotic stresses especially hypersaline conditions We have grown the cells in three different salt concentrations 15M NaClcontrol 2M NaCl and 3M NaCl hypersaline Fast chlorophyll fluorescence analysis showed increased initial fluorescence Fo and decreased photosynthetic efficiency indicating hampered PSII utilization capacity under hypersaline conditions Also the ROS localization studies and quantification revealed elevated accumulation of ROS in the chloroplast in the 3M condition Pigment analysis shows a deficit in chlorophyll content and increased carotenoid accumulation especially lutein and zeaxanthin content This study majorly explored the chloroplast transcripts of the D salina cell as it is the major environmental sensor Even though most of the photosystem subunit transcripts showed moderate upregulation in hypersaline conditions in the transcriptome study the western blot analysis showed degradation of the core as well as antenna proteins of both the photosystems Among the upregulated chloroplast transcripts Chloroplast Tidi flavodoxin IsiB and carotenoid biosynthesisrelated protein CBR transcripts strongly proposed photosynthetic apparatus remodeling Also the transcriptomic study revealed the upregulation of the tetrapyrrole biosynthesis pathway TPB and identified the presence of a negative regulator of this pathway called the sFLP splicing variant These observations point towards the accumulation of TPB pathway intermediates PROTOIX Mg PROTOIX and PChlide those earlier reported as retrograde signaling molecules Our comparative transcriptomic approach along with biophysical and biochemical studies in D salina grown under control 15 M NaCl and hypersaline 3M NaCl conditions unveil an efficient retrograde signaling mechanism mediated remodeling of photosynthetic apparatus