RcDhn5, a cold acclimation‐responsive dehydrin from Rhododendron catawbiense rescues enzyme activity from dehydration effects in vitro and enhances freezing tolerance in RcDhn5‐overexpressing Arabidopsis plants

Abstract

Dehydrins (DHNs) are typically induced in response to abiotic stresses that impose cellular dehydration. As extracellular freezing results in cellular dehydration, accumulation of DHNs and development of desiccation tolerance are believed to be key components of the cold acclimation (CA) process. The present study shows that RcDhn5, one of the DHNs from Rhododendron catawbiense leaf tissues, encodes an acidic, SK 2 type DHN and is upregulated during seasonal CA and downregulated during spring deacclimation (DA). Data from in vitro partial water loss assays indicate that purified RcDhn5 protects enzyme activity against a dehydration treatment and that this protection is comparable with acidic SK n DHNs from other species. To investigate the contribution of RcDhn5 to freezing tolerance (FT), Arabidopsis plants overexpressing RcDhn5 under the control of 35S promoter were generated. Transgenic plants exhibited improved 'constitutive' FT compared with the control plants. Furthermore, a small but significant improvement in FT of RcDhn5-overexpressing plants was observed after 12 h of CA; however, this gained acclimation capacity was not sustained after a 6-day CA. Transcript profiles of cold-regulated native Arabidopsis DHNs (COR47, ERD10 and ERD14) during a CA time-course suggests that the apparent lack of improvement in cold-acclimated FTof RcDhn5-overexpressing plants over that of wild-type controls after a 6-day CA might have been because of the dilution of the effect of RcDhn5 overproduction by a strong CA-induced expression of native Arabidopsis DHNs. This study provides evidence that RcDhn5 contributes to freezing stress tolerance and that this could be, in part, because of its dehydration stress-protective ability.

Identification and characterization of genes encoding two novel LEA proteins in Antarctic and temperate strains of Chlorella vulgaris

“…We hypothesized that the difference in freezing tolerance is due to differences in contents of antifreeze or cryoprotective proteins in cells. Before our studies, LEA proteins had been found to be correlated to the anti-freeze capacities of some higher plants (Minami et al, 2005;Rorat et al, 2006;Nakayama et al, 2007;Peng et al, 2008). In this study, we showed that the levels of Ccor1 and Ccor2 were correlated to the freeze tolerance in the two Chlorella strains.…”

“…The adaptive strategies include increasing membrane fluidity (Henderson et al, 1998;Mock and Kroon, 2002;Thomson et al, 2004), producing cold-adapted enzymes (Loppes et al, 1996;di Rigano et al, 2006), accumulating antifreeze proteins and cryoprotectants (Gilbert et al, 2004;D'Amico et al, 2006). Some studies have shown that accumulated LEA (late embryogenesis abundant) proteins can act as cryoprotectants and enhance the freezing tolerance in plants (Honjoh et al 1999;Kim et al, 2005;Peng et al, 2008).…”

Proteomic Study of Low-Temperature Responses in Strawberry Cultivars (Fragaria×ananassa) That Differ in Cold Tolerance

“…The expression of dehydrins is highly correlated with cold-stress tolerance in a number of plant species (Hara et al, 2003;Renaut et al, 2004;Peng et al, 2008) including strawberry (Houde et al, 2004). The levels of some of these proteins are controlled by the coldresponse pathway CBF transcription factors (Lee et al, 2005).…”

The Importance of Size and Disorder in the Cryoprotective Effects of Dehydrins

“…These motifs are poorly conserved in terms of their length and sequences and tend to be located between other segments (Close, 1996(Close, , 1997. Overall, dehydrin sequences are highly hydrophilic and generally lack Cys or Trp residues, although one dehydrin has been discovered to have Cys residues (Peng et al, 2008;Reyes et al, 2008). Not surprisingly, the high polar content results in dehydrins being intrinsically disordered proteins (IDPs; Hughes and Graether, 2011), and as such, they do not have a single, well-defined protein structure (Lisse et al, 1996;Tompa, 2002;Uversky, 2002a).…”