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made in order to annotate genes from seagrasses. The rapidly increasing literature
on the molecular biology of seagrasses is mainly supported by gene annotations of
terrestrial plants such as Arabidopsis thaliana, Oryza sativa, Vitis vinifera, etc. This
is quite reasonable, taking into account the fact that the first complete plant genome
to be determined was that of the plant Arabidopsis thaliana, which is available since
2000 (Arabidopsis Genome 2000), while a well-annotated genome for seagrass species is not available yet in public databases. In that sense, the assignment of
sequenced unigenes in the adequate biochemical pathways could be somewhat
tricky. Genomic information on seagrass species is continuously enriched, and the
first genome sequenced was that of Zostera marina (Olsen et al. 2016), which produced important outcomes for seagrass genomics, although genome sizes vary
among seagrasses (Koce et al. 2003), with that of Posidonia oceanica being substantially larger than that of Zostera marina. This is to date attributed to the number
and length of chromosomes, transposable elements, repetitive regions, etc.
Therefore, genomic information on different seagrass species will help out the scientific community unravel the evolutionary forces exerted on the seagrasses.
Seagrasses colonized the marine environment and formed a widespread and
highly important specific habitat. During this transition, gene gains and losses
shaped their ability to survive and boom in the sea. Gene gains facilitated processes
such as ion regulation, nutrient uptake, and O 2 /CO 2 exchange. In other words, these
operational modes render seagrasses to survive in elevated salinities. Their cell
walls contain low-methylated pectins and sulfated galactans (Aquino et al. 2005),
features interestingly shared with macroalgae. On the other hand, gene families
implicated in stomatal development, ethylene and terpenoid biosynthesis, ultraviolet protection, and far-red sensing have been all over omitted (Kong et al. 2014;
Golicz et al. 2015; Lee et al. 2016; Olsen et al. 2016).
Life on the seabed is associated with anatomical adaptations such as lack of stomata. Their surfaces are covered by a thin cuticle, across which the gas and nutrient
transfer takes place (Hemminga and Duarte 2000; Kuo and Den Hartog 2007).
Seagrasses retained the ability to exchange gases with their environment with
“algal-like” cell walls. In Arabidopsis EPF1/2 genes act as regulators of stomatal
development by interacting with the leucine-rich repeat-containing receptor-like
protein TMM (Nadeau and Sack 2002; Hunt and Gray 2009). The SPEECHLESS
(SPCH) gene, which regulates the expression of both TMM and EPF1/2, and the
SCREAM2 (SCRM2), which contribute toward meristemoid formation, have been
omitted in Zostera marina. The entire pathway that differentiates meristemoid
mother cells (MMC) to guard cells, which are produced to form stomata, has been
lost (Olsen et al. 2016).
Another molecular pathway lost in Zostera marina is that of ethylene biosynthesis and signaling (Olsen et al. 2016). Ethylene is an important phytohormone in
terrestrial plants, since it has been demonstrated that it enhances maturation and
modulates cell division in Arabidopsis sp. roots (Ortega-Martinez et al. 2007). The
genome of Zostera marina became the cornerstone among the large-scale studies
trying to elucidate seagrass evolution and transition to the sea.
E.E. Malandrakis et al.
made in order to annotate genes from seagrasses. The rapidly increasing literature
on the molecular biology of seagrasses is mainly supported by gene annotations of
terrestrial plants such as Arabidopsis thaliana, Oryza sativa, Vitis vinifera, etc. This
is quite reasonable, taking into account the fact that the first complete plant genome
to be determined was that of the plant Arabidopsis thaliana, which is available since
2000 (Arabidopsis Genome 2000), while a well-annotated genome for seagrass species is not available yet in public databases. In that sense, the assignment of
sequenced unigenes in the adequate biochemical pathways could be somewhat
tricky. Genomic information on seagrass species is continuously enriched, and the
first genome sequenced was that of Zostera marina (Olsen et al. 2016), which produced important outcomes for seagrass genomics, although genome sizes vary
among seagrasses (Koce et al. 2003), with that of Posidonia oceanica being substantially larger than that of Zostera marina. This is to date attributed to the number
and length of chromosomes, transposable elements, repetitive regions, etc.
Therefore, genomic information on different seagrass species will help out the scientific community unravel the evolutionary forces exerted on the seagrasses.
Seagrasses colonized the marine environment and formed a widespread and
highly important specific habitat. During this transition, gene gains and losses
shaped their ability to survive and boom in the sea. Gene gains facilitated processes
such as ion regulation, nutrient uptake, and O 2 /CO 2 exchange. In other words, these
operational modes render seagrasses to survive in elevated salinities. Their cell
walls contain low-methylated pectins and sulfated galactans (Aquino et al. 2005),
features interestingly shared with macroalgae. On the other hand, gene families
implicated in stomatal development, ethylene and terpenoid biosynthesis, ultraviolet protection, and far-red sensing have been all over omitted (Kong et al. 2014;
Golicz et al. 2015; Lee et al. 2016; Olsen et al. 2016).
Life on the seabed is associated with anatomical adaptations such as lack of stomata. Their surfaces are covered by a thin cuticle, across which the gas and nutrient
transfer takes place (Hemminga and Duarte 2000; Kuo and Den Hartog 2007).
Seagrasses retained the ability to exchange gases with their environment with
“algal-like” cell walls. In Arabidopsis EPF1/2 genes act as regulators of stomatal
development by interacting with the leucine-rich repeat-containing receptor-like
protein TMM (Nadeau and Sack 2002; Hunt and Gray 2009). The SPEECHLESS
(SPCH) gene, which regulates the expression of both TMM and EPF1/2, and the
SCREAM2 (SCRM2), which contribute toward meristemoid formation, have been
omitted in Zostera marina. The entire pathway that differentiates meristemoid
mother cells (MMC) to guard cells, which are produced to form stomata, has been
lost (Olsen et al. 2016).
Another molecular pathway lost in Zostera marina is that of ethylene biosynthesis and signaling (Olsen et al. 2016). Ethylene is an important phytohormone in
terrestrial plants, since it has been demonstrated that it enhances maturation and
modulates cell division in Arabidopsis sp. roots (Ortega-Martinez et al. 2007). The
genome of Zostera marina became the cornerstone among the large-scale studies
trying to elucidate seagrass evolution and transition to the sea.
E.E. Malandrakis et al.