24
transcriptomic analyses found that the reduction in actin quantity was due to an
upregulation of a cofilin/actin depolymerizing factor (Holzinger et al. 2011; LópezCristoffanini et al. 2015; Fierro et al. 2017). This factor disassembles actin filaments
and prevents denaturation, thereby maintaining an actin pool in the cell (Maciver and
Hussey 2002). Further ultrastructural analyses of both desiccated Py. orbicularis and
K. crenulatum evidenced tissues with irregular contours, plasma membrane folding,
and a notable accumulation of electron-dense bodies inside the chloroplast. These
observations support that cytoplasmic components, such as compatible solutes,
agglomerate, and cytoplasm viscosity, increase when the cellular water content is
low. Both effects decrease the probability of molecular interactions that may cause
protein denaturation and membrane fusion.
Proteins associated with the synthesis of compatible solutes, including triosephosphate isomerase, S-adenosylmethionine synthetase, GDP-D-mannose-3′,5′epimerase, and phosphomannomutase, occur in desiccated Py. orbicularis. Due to
the inability of red algae such as Py. orbicularis to produce sucrose, triosephosphate isomerase could be important in glycerol synthesis, which couples with
d-galactose to form floridoside and isofloridoside, the primary photosynthates.
S-adenosylmethionine synthetase, which is upregulated in plants and algae exposed
to stress, synthesizes adenosylmethionine, a cofactor in the synthesis of compatible solutes such as glycine betaine. Thus, the recovery of cellular volume and
conformation could be due to the intricate coordination of mechanisms, such as
compatible solutes production, channel activation, and an efficient dismantling
and assembly of the cytoskeleton present in desiccation-tolerant species.
2.2.3 Increased Expression of Desiccation-Associated Proteins
In resurrection plants, desiccation stress increases the production of heat shock and
late embryogenesis abundant proteins (Scott 2000; Alpert 2005; Leprince and
Buitink 2010). These protein groups are possible desiccation tolerance chaperones
that avert macromolecule aggregation and maintain the proper conformations and
activities of other proteins (Timperio et al. 2008; Toldi et al. 2009). These proteins
have also been associated with internal cellular structures, such as cytoskeleton filaments that maintain cell stability. Furthermore, these proteins act as water substitute
given a high glycine content (ca. >6%) (Oliver and Bewley 1997; Hoekstra et al.
2001). Desiccated Py. orbicularis overproduces heat shock proteins and chaperones
(e.g., chaperonin 60, GRP78, BiP, and KAR2) (Contreras-Porcia et al. 2013; LópezCristoffanini et al. 2015). Likewise, the green alga Asterochloris erici (Trebouxiales)
overproduces five heat shock protein 90 transcripts under desiccation (Gasulla et al.
2013; Holzinger and Karsten 2013). In addition, increased peptidylprolyl isomerase
production was detected in desiccated Py. orbicularis using a proteomic approach
(López-Cristoffanini et al. 2015). This enzyme rotates the peptide bonds prior to
proline to induce protein folding and prevent water loss damage (Baniwal et al.
2004). Thus, although the available literature regarding algae desiccation-associated proteins is not as extensive as that of resurrection plants, a careful review of the
L. Contreras-Porcia et al.
transcriptomic analyses found that the reduction in actin quantity was due to an
upregulation of a cofilin/actin depolymerizing factor (Holzinger et al. 2011; LópezCristoffanini et al. 2015; Fierro et al. 2017). This factor disassembles actin filaments
and prevents denaturation, thereby maintaining an actin pool in the cell (Maciver and
Hussey 2002). Further ultrastructural analyses of both desiccated Py. orbicularis and
K. crenulatum evidenced tissues with irregular contours, plasma membrane folding,
and a notable accumulation of electron-dense bodies inside the chloroplast. These
observations support that cytoplasmic components, such as compatible solutes,
agglomerate, and cytoplasm viscosity, increase when the cellular water content is
low. Both effects decrease the probability of molecular interactions that may cause
protein denaturation and membrane fusion.
Proteins associated with the synthesis of compatible solutes, including triosephosphate isomerase, S-adenosylmethionine synthetase, GDP-D-mannose-3′,5′epimerase, and phosphomannomutase, occur in desiccated Py. orbicularis. Due to
the inability of red algae such as Py. orbicularis to produce sucrose, triosephosphate isomerase could be important in glycerol synthesis, which couples with
d-galactose to form floridoside and isofloridoside, the primary photosynthates.
S-adenosylmethionine synthetase, which is upregulated in plants and algae exposed
to stress, synthesizes adenosylmethionine, a cofactor in the synthesis of compatible solutes such as glycine betaine. Thus, the recovery of cellular volume and
conformation could be due to the intricate coordination of mechanisms, such as
compatible solutes production, channel activation, and an efficient dismantling
and assembly of the cytoskeleton present in desiccation-tolerant species.
2.2.3 Increased Expression of Desiccation-Associated Proteins
In resurrection plants, desiccation stress increases the production of heat shock and
late embryogenesis abundant proteins (Scott 2000; Alpert 2005; Leprince and
Buitink 2010). These protein groups are possible desiccation tolerance chaperones
that avert macromolecule aggregation and maintain the proper conformations and
activities of other proteins (Timperio et al. 2008; Toldi et al. 2009). These proteins
have also been associated with internal cellular structures, such as cytoskeleton filaments that maintain cell stability. Furthermore, these proteins act as water substitute
given a high glycine content (ca. >6%) (Oliver and Bewley 1997; Hoekstra et al.
2001). Desiccated Py. orbicularis overproduces heat shock proteins and chaperones
(e.g., chaperonin 60, GRP78, BiP, and KAR2) (Contreras-Porcia et al. 2013; LópezCristoffanini et al. 2015). Likewise, the green alga Asterochloris erici (Trebouxiales)
overproduces five heat shock protein 90 transcripts under desiccation (Gasulla et al.
2013; Holzinger and Karsten 2013). In addition, increased peptidylprolyl isomerase
production was detected in desiccated Py. orbicularis using a proteomic approach
(López-Cristoffanini et al. 2015). This enzyme rotates the peptide bonds prior to
proline to induce protein folding and prevent water loss damage (Baniwal et al.
2004). Thus, although the available literature regarding algae desiccation-associated proteins is not as extensive as that of resurrection plants, a careful review of the
L. Contreras-Porcia et al.