1 research outputs found
The modulation of leaf metabolism plays a role in salt tolerance of Cymodocea nodosa exposed to hypersaline stress in mesocosms
Applying proteomics, we tested the physiological responses of the euryhaline seagrass
Cymodocea nodosa to deliberate manipulation of salinity in a mesocosm system.
Plants were subjected to a chronic hypersaline condition (43 psu) to compare protein
expression and plant photochemistry responses after 15 and 30 days of exposure
with those of plants cultured under normal/ambient saline conditions (37 psu). Results
showed a general decline in the expression level of leaf proteins in hypersaline stressed
plants, with more intense reductions after long-lasting exposure. Specifically, the
carbon-fixing enzyme RuBisCo displayed a lower accumulation level in stressed plants
relative to controls. In contrast, the key enzymes involved in the regulation of glycolysis,
cytosolic glyceraldehyde-3-phosphate dehydrogenase, enolase 2 and triose-phosphate
isomerase, showed significantly higher accumulation levels. These responses suggested
a shift in carbon metabolism in stressed plants. Hypersaline stress also induced a
significant alteration of the photosynthetic physiology of C. nodosa by means of a downregulation
in structural proteins and enzymes of both PSII and PSI. However we found
an over-expression of the cytochrome b559 alpha subunit of the PSII initial complex,
which is a receptor for the PSII core proteins involved in biogenesis or repair processes
and therefore potentially involved in the absence of effects at the photochemical level
of stressed plants. As expected hypersalinity also affects vacuolar metabolism by
increasing the leaf cell turgor pressure and enhancing the up-take of Na+ by overaccumulating
the tonoplast specific intrinsic protein pyrophosphate-energized inorganic
pyrophosphatase (H(+)-PPase) coupled to the Na+/H+-antiporter. The modulation of
carbon metabolism and the enhancement of vacuole capacity in Na+ sequestration and
osmolarity changes are discussed in relation to salt tolerance of C. nodosa.Postprin