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Understanding the cellular mechanism of recovery from freeze–thaw injury in spinach: possible role of aquaporins, heat shock proteins, dehydrin and antioxidant system
Author(s) -
Chen Keting,
Arora Rajeev
Publication year - 2014
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/ppl.12090
Subject(s) - apx , catalase , spinacia , superoxide dismutase , heat shock protein , peroxidase , biochemistry , antioxidant , extracellular , chemistry , spinach , biophysics , biology , enzyme , chloroplast , gene
Recovery from reversible freeze–thaw injury in plants is a critical component of ultimate frost survival. However, little is known about this aspect at the cellular level. To explore possible cellular mechanism(s) for post‐thaw recovery (REC), we used Spinacia oleracea L. cv. Bloomsdale leaves to first determine the reversible freeze–thaw injury point. Freeze (–4.5°C)–thaw‐injured tissues (32% injury vs <3% in unfrozen control) fully recovered during post‐thaw, as assessed by an ion leakage‐based method. Our data indicate that photosystem II efficiency (Fv/Fm) was compromised in injured tissues but recovered during post‐thaw. Similarly, the reactive oxygen species (O 2 •− and H 2 O 2 ) accumulated in injured tissues but dissipated during recovery, paralleled by the repression and restoration, respectively, of activities of antioxidant enzymes, superoxide dismutase ( SOD ) ( EC . 1.14.1.1), and catalase ( CAT ) ( EC .1.11.1.6) and ascorbate peroxidase ( APX ) ( EC .1.11.1.11). Restoration of CAT and APX activities during recovery was slower than SOD , concomitant with a slower depletion of H 2 O 2 compared to O 2 •− . A hypothesis was also tested that the REC is accompanied by changes in the expression of water channels [aquaporines ( AQPs )] likely needed for re‐absorption of thawed extracellular water. Indeed, the expression of two spinach AQPs , SoPIP2 ;1 and SoδTIP , was downregulated in injured tissues and restored during recovery. Additionally, a notion that molecular chaperones [heat shock protein of 70 kDa ( HSP70s )] and putative membrane stabilizers [dehydrins ( DHNs )] are recruited during recovery to restore cellular homeostasis was also tested. We noted that, after an initial repression in injured tissues, the expression of three HSP70 s (cytosolic, endoplasmic reticulum and mitochondrial) and a spinach DHN ( CAP85 ) was significantly restored during the REC.