Tissue-specific modulation of functional stress responsive proteins and organic osmolytes by a single or dual short-term high CO₂ treatment during long-term cold storage Autumn Royal table grapes

Plant cell response to damage from environmental stressors that cause dehydration involves stress-related proteins and osmotically active compounds whose constitutive levels increase in association with the tolerance response mechanism. In table grape postharvest scope, the application of a second 3 d 20 kPa CO2 treatment significantly reduced the incidence and severity of long-term cold postharvest storage disorders in Autumn Royal cv. counteracting ultrastructural cell damage and restraining intracellular and membrane oxidative stress. In this sense, it may be of relevance to postharvest quality to know how this dual short-term high CO2 treatment modulates the cell stress responsive defense strategies, and whether these are tissue-dependent and timingregulated. In this work, we studied the differential profile of protective osmolytes proline, glycine betaine, & gamma;-aminobutyric acid and trehalose in the berry tissues. Likewise, we assessed the temporal and spatial expression and accumulation patterns of the thaumatin-like protein (VviTL1, VviOsmo) and dehydrin (VviDHN1a, VviDHN4, VviDHN2, VviDHN2D) isoforms in the whole berry tissues and rachis of cv. Autumn Royal table grapes during long-term cold storage period and evaluated the profile-shift by CO2 treatments. Their subcellular localization in the pericarp tissues was also determined by immunocytochemical transmission electron microscopy (TEM). The results showed that the cold-drought defense strategies activated by the short-term high CO2 are dose-dependent, tissue-specific and transcriptionally timing-regulated during long-term postharvest cold storage period in table grapes. The results also showed that the more short-term high CO2 treatment is applied to Autumn Royal grapes, the more microstructural evidence there is of enhanced tolerance to storage disorders in terms of thicker and denser cell wall that could contribute to restrain swelling, dehydration and osmotic stress.