59
2006; Nagle and Gerwick 1990; Proteau and Gerwick 1993; Rempt et al. 2012;
Weinberger et al. 2011). Phytoprostanes nonenzymatically derived from ALA have
also been identified in seaweeds (Barbosa et al. 2015; Ritter et al. 2014). The occurrence and distribution of naturally occurring free phytoprostanes has been found to be
highly unpredictable differing between species and as a consequence of the surrounding growth conditions, with F 1t -phytoprostanes (including both 9-F 1t -phytoprostane
and 9-epi-9-F 1t -phytoprostane) being the dominant and L1-phytoprostanes the minor
class (Barbosa et al. 2015). Recently, methyl jasmonate (MeJA) enzymatically derived
from ALA by LOX pathway has been detected and quantified for the first time, from
the cystocarps of red seaweed Grateloupia imbricata Holmes (Pilar et al. 2016) that
releases this volatile compound in significant amounts (1.27 ± 0.20 mM • mg fw
−1
•
h
−1
in fertile thalli and 0.95 ± 0.12 mM • mg fw
−1
• h
−1
in infertile thalli).
Seaweed oxylipins play various important roles in growth regulation and
defense and confer innate immunity in response to biotic and abiotic stresses
such as pathogenic bacteria, herbivores, wounding, and metal toxicity in seaweeds (Bouarab et al. 2004; Gaquerel et al. 2007; Küpper et al. 2006, 2009; Lion
et al. 2006; Nylund et al. 2011; Rempt et al. 2012; Ritter et al. 2008; Weinberger
et al. 2011). However, most of the information available regarding seaweed oxylipins has come from the metabolic studies rather than the genomic studies due
to limited number of available seaweed genome sequences as compared to higher
plants and microalgae. Consequently, only four putative LOX sequences are
available in NCBI database isolated from C. crispus (accession number
XM_005718216.1), Ectocarpus siliculosus (Dillwyn) Lyngbye (Cock et al.
2010), Gracilaria chilensis C. J. Bird, McLachlan & E. C. Oliveira (accession
number JF896804), Porphyra purpurea (Roth) C. Agardh (Liu and Reith 1994),
Pyropia haitanensis (T. J. Chang & B. F. Zheng) N. Kikuchi & M. Miyata (accession number JX188386), and one AOC sequence in E. siliculosus (Cock et al.
2010). Besides the ecophysiological role of these oxidized lipid derivatives and
their relevance in seaweeds, the exact mechanisms of stress tolerance are not
known. Moreover, and because metabolites of this class also play a crucial role
in both mammalian physiology and disease, interest in the structural chemistry,
biosynthesis, and pharmacological activities of these marine products has
increased. With present context, there is a need to improve our knowledge of the
pathways of oxylipin biosynthesis, their individual role in cellular responses, and
the target elements involved in gene regulation, which can only be achieved
using the systems biology approach of combined genomics, transcriptomics, and
metabolomics/lipidomics tools.
4.2.7 Sterols
Sterols are important structural components of cell membranes that regulate membrane fluidity and permeability. They are amphipathic compounds that originate in
isoprenoid biosynthesis forming a group of triterpenes with a tetracyclic
4 Seaweed Lipidomics in the Era of ‘Omics’ Biology: A Contemporary Perspective
2006; Nagle and Gerwick 1990; Proteau and Gerwick 1993; Rempt et al. 2012;
Weinberger et al. 2011). Phytoprostanes nonenzymatically derived from ALA have
also been identified in seaweeds (Barbosa et al. 2015; Ritter et al. 2014). The occurrence and distribution of naturally occurring free phytoprostanes has been found to be
highly unpredictable differing between species and as a consequence of the surrounding growth conditions, with F 1t -phytoprostanes (including both 9-F 1t -phytoprostane
and 9-epi-9-F 1t -phytoprostane) being the dominant and L1-phytoprostanes the minor
class (Barbosa et al. 2015). Recently, methyl jasmonate (MeJA) enzymatically derived
from ALA by LOX pathway has been detected and quantified for the first time, from
the cystocarps of red seaweed Grateloupia imbricata Holmes (Pilar et al. 2016) that
releases this volatile compound in significant amounts (1.27 ± 0.20 mM • mg fw
−1
•
h
−1
in fertile thalli and 0.95 ± 0.12 mM • mg fw
−1
• h
−1
in infertile thalli).
Seaweed oxylipins play various important roles in growth regulation and
defense and confer innate immunity in response to biotic and abiotic stresses
such as pathogenic bacteria, herbivores, wounding, and metal toxicity in seaweeds (Bouarab et al. 2004; Gaquerel et al. 2007; Küpper et al. 2006, 2009; Lion
et al. 2006; Nylund et al. 2011; Rempt et al. 2012; Ritter et al. 2008; Weinberger
et al. 2011). However, most of the information available regarding seaweed oxylipins has come from the metabolic studies rather than the genomic studies due
to limited number of available seaweed genome sequences as compared to higher
plants and microalgae. Consequently, only four putative LOX sequences are
available in NCBI database isolated from C. crispus (accession number
XM_005718216.1), Ectocarpus siliculosus (Dillwyn) Lyngbye (Cock et al.
2010), Gracilaria chilensis C. J. Bird, McLachlan & E. C. Oliveira (accession
number JF896804), Porphyra purpurea (Roth) C. Agardh (Liu and Reith 1994),
Pyropia haitanensis (T. J. Chang & B. F. Zheng) N. Kikuchi & M. Miyata (accession number JX188386), and one AOC sequence in E. siliculosus (Cock et al.
2010). Besides the ecophysiological role of these oxidized lipid derivatives and
their relevance in seaweeds, the exact mechanisms of stress tolerance are not
known. Moreover, and because metabolites of this class also play a crucial role
in both mammalian physiology and disease, interest in the structural chemistry,
biosynthesis, and pharmacological activities of these marine products has
increased. With present context, there is a need to improve our knowledge of the
pathways of oxylipin biosynthesis, their individual role in cellular responses, and
the target elements involved in gene regulation, which can only be achieved
using the systems biology approach of combined genomics, transcriptomics, and
metabolomics/lipidomics tools.
4.2.7 Sterols
Sterols are important structural components of cell membranes that regulate membrane fluidity and permeability. They are amphipathic compounds that originate in
isoprenoid biosynthesis forming a group of triterpenes with a tetracyclic
4 Seaweed Lipidomics in the Era of ‘Omics’ Biology: A Contemporary Perspective