140
Schliep et al. 2015). In these work, seagrasses under low light condition exhibited
downregulation of PSI gene expression (PSI reaction center subunit V in Dattolo
et al. 2014 and PS I reaction center subunit IV B in Schliep et al. 2015). Although
the physiological and molecular mechanisms of these differentially expressed genes
and proteins remain unclear, these cited research provide a basis for further investigation of seagrass molecular adaptation to limiting light.
On the contrary, intertidal and shallow subtidal species might experience periodic or prolonged high irradiance during low tides (Ralph and Burchett 1995;
Hanelt and Figueroa 2012). At the physiological level, fast chlorophyll fluorescence
induction curves revealed a closure of PSII reaction centers, which likely contributed to the decline in effective quantum efficiency under higher irradiance (York
et al. 2013). To prevent photodamage due to high light, plants use different photoprotection strategies. Lowering light perception by reducing light-harvesting
antenna size measured as chlorophyll b/a ratio was reported in P. oceanica (Dattolo
et al. 2014). At the molecular level, Dattolo et al. (2013, 2014) highlighted the possible roles of chlorophyll a/b-binding proteins (CABs) and Rubisco activase in
photoprotection and photoacclimation of the seagrass P. oceanica. In these works,
seagrasses growing in deep (lower light intensity) and shallow (higher light intensity)
sites exhibited distinct transcriptional and proteomic profiles regarding CABs
(Dattolo et al. 2014): transcript level of chlorophyll a/b-binding proteins (chlorophyll a/b-binding protein 1 (Pooc_B_c293), 21 (Pooc_B_c132), 131 (Pooc_B_
c386)) was found to be higher in the seagrass growing in shallow site. CABs are
thought to involve in light-harvesting regulation under different light conditions,
and certain members of CAB family have been proposed to play a photoprotective
role via state transition (Pietrzykowska et al. 2014) and excess light energy dissipation (Li et al. 2000). Dattolo et al. (2013) also reported higher protein level of
Rubisco activase in the seagrass growing in shallow site. Rubisco activase regulates
photosynthesis by modulating Rubisco activation under various conditions, and its
activity has been shown to increase with light intensity (Lan et al. 1992; Portis
2003). Additionally, xanthophyll cycle has been proposed to serve a role in excess
energy dissipation in various seagrass species such as Z. capricorni (Flanigan and
Critchley 1996), Z. marina (Ralph et al. 2002), P. sinuosa (Collier et al. 2008), T.
testudinum (Howarth and Durako 2013), P. oceanica, and C. nodosa (Marín-Guirao
et al. 2013a; Dattolo et al. 2014). At the molecular level, P. oceanica in shallow
areas show an upregulation of the xanthophyll cycle-related gene, zeaxanthin deepoxidase, as well as an increase in violaxanthin and a consequential increase in the
sum of xanthophyll cycle pigment pool compared to the deep meadow. Additionally,
a few works have proposed that anthocyanin also serve a role in photoprotection in
seagrasses. Anthocyanin accumulation in leaves has been widely reported in various
seagrass species in the intertidal to the shallow subtidal area across the tropical
bioregions (Novak and Short 2010; Ragavan et al. 2013; Kaewsrikhaw and Prathep
2014). Novak and Short (2011a, b, 2012) conducted extensive studies on the role of
anthocyanin in T. testudinum (from Florida Keys, USA). From these observations,
it was concluded that anthocyanin accumulation provides photoprotection for T.
testudinum by absorbing both ultraviolet (absorption maxima 280 nm) and visible
P. Buapet
Schliep et al. 2015). In these work, seagrasses under low light condition exhibited
downregulation of PSI gene expression (PSI reaction center subunit V in Dattolo
et al. 2014 and PS I reaction center subunit IV B in Schliep et al. 2015). Although
the physiological and molecular mechanisms of these differentially expressed genes
and proteins remain unclear, these cited research provide a basis for further investigation of seagrass molecular adaptation to limiting light.
On the contrary, intertidal and shallow subtidal species might experience periodic or prolonged high irradiance during low tides (Ralph and Burchett 1995;
Hanelt and Figueroa 2012). At the physiological level, fast chlorophyll fluorescence
induction curves revealed a closure of PSII reaction centers, which likely contributed to the decline in effective quantum efficiency under higher irradiance (York
et al. 2013). To prevent photodamage due to high light, plants use different photoprotection strategies. Lowering light perception by reducing light-harvesting
antenna size measured as chlorophyll b/a ratio was reported in P. oceanica (Dattolo
et al. 2014). At the molecular level, Dattolo et al. (2013, 2014) highlighted the possible roles of chlorophyll a/b-binding proteins (CABs) and Rubisco activase in
photoprotection and photoacclimation of the seagrass P. oceanica. In these works,
seagrasses growing in deep (lower light intensity) and shallow (higher light intensity)
sites exhibited distinct transcriptional and proteomic profiles regarding CABs
(Dattolo et al. 2014): transcript level of chlorophyll a/b-binding proteins (chlorophyll a/b-binding protein 1 (Pooc_B_c293), 21 (Pooc_B_c132), 131 (Pooc_B_
c386)) was found to be higher in the seagrass growing in shallow site. CABs are
thought to involve in light-harvesting regulation under different light conditions,
and certain members of CAB family have been proposed to play a photoprotective
role via state transition (Pietrzykowska et al. 2014) and excess light energy dissipation (Li et al. 2000). Dattolo et al. (2013) also reported higher protein level of
Rubisco activase in the seagrass growing in shallow site. Rubisco activase regulates
photosynthesis by modulating Rubisco activation under various conditions, and its
activity has been shown to increase with light intensity (Lan et al. 1992; Portis
2003). Additionally, xanthophyll cycle has been proposed to serve a role in excess
energy dissipation in various seagrass species such as Z. capricorni (Flanigan and
Critchley 1996), Z. marina (Ralph et al. 2002), P. sinuosa (Collier et al. 2008), T.
testudinum (Howarth and Durako 2013), P. oceanica, and C. nodosa (Marín-Guirao
et al. 2013a; Dattolo et al. 2014). At the molecular level, P. oceanica in shallow
areas show an upregulation of the xanthophyll cycle-related gene, zeaxanthin deepoxidase, as well as an increase in violaxanthin and a consequential increase in the
sum of xanthophyll cycle pigment pool compared to the deep meadow. Additionally,
a few works have proposed that anthocyanin also serve a role in photoprotection in
seagrasses. Anthocyanin accumulation in leaves has been widely reported in various
seagrass species in the intertidal to the shallow subtidal area across the tropical
bioregions (Novak and Short 2010; Ragavan et al. 2013; Kaewsrikhaw and Prathep
2014). Novak and Short (2011a, b, 2012) conducted extensive studies on the role of
anthocyanin in T. testudinum (from Florida Keys, USA). From these observations,
it was concluded that anthocyanin accumulation provides photoprotection for T.
testudinum by absorbing both ultraviolet (absorption maxima 280 nm) and visible
P. Buapet