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seaweeds can only be explained with integrated systems biology approach of lipidomics, genomics, and proteomics.
Jasmonates are lipid-derived signal molecules belonging to oxylipin class that
mediates a plethora of biological processes from stress and defense responses to
reproductive development, secondary metabolism, and senescence in plants
(Browse 2009; Wasternack et al. 2012). They are generated via the allene oxide
synthase (AOS) branch of the lipoxygenase (LOX) pathway of lipid oxidation and
exert their effects by orchestrating large-scale reprogramming of gene expression
(Kombrink 2012). Methyl jasmonate (MeJA) is one of the most active forms of
jasmonic acid in plants produced by methyl ester formation on C1 of JA by
JA-specific methyltransferase (Seo et al. 2001). Numerous studies have implicated the roles of MeJA in defense against biotic/abiotic stresses in seaweeds
including C. crispus (Bouarab et al. 2004; Collén et al. 2013; Gaquerel et al.
2007), Fucus vesiculosus Linnaeus (Arnold et al. 2001), Laminaria digitata
(Hudson) J. V. Lamouroux (Küpper et al. 2009), and G. dura (Kumari et al. 2015).
However, it was unclear if MeJA was an endogenous compound in these seaweeds
until the recent report of MeJA release from the cystocarps of Grateloupia imbricata Holmes (Pilar et al. 2016). MeJA was earlier only detected in Gelidium latifolium Bornet ex Hauck (Krupina and Dathe 1991), and all other attempts to
detect MeJA in seaweeds (Chondrus, Colpomenia, Dictyota, Ectocarpus, Fucus,
Himanthalia, Saccharina, and Sargassum) were not successful (Bouarab et al.
2004; Wiesemeier et al. 2008). Further, adding to the complexity of MeJA pathway in seaweeds, the entire set of enzymes necessary for the biosynthesis of JA
from ALA has been identified in Gracilariopsis sp. (Hamberg and Gerwick 1993)
and Lithothamnion corallioides (P. Crouan & H. Crouan) P. Crouan & H. Crouan
(Hamberg 1992). The genome sequence of E. siliculosus (Cock et al. 2010) also
showed the candidate genes for AOS, which catalyzes the initial step of JA biosynthesis and allene oxide cyclase (AOC). On contrary, no candidate genes could
be identified for AOS and AOC in the genome of the red alga C. crispus, which
contained two candidate genes for 12-oxo-phytodienoic acid reductase (12-OPR)
and genes involved in ß-oxidation within the JA biosynthetic pathway (Collén
et al. 2013). Moreover, no genes for jasmonic acid carboxyl methyl transferase
have been identified in the genome of both the seaweeds indicating that an enzyme
different from those characterized in land plants may be present in these seaweeds
(Cock et al. 2010; Collén et al. 2013). No consensus is present in the scientific
community about the occurrence and physiological relevance of MeJA in seaweeds. The combined genomics, transcriptomics, proteomics, and lipidomics
study could only unveil the jasmonic acid/methyl jasmonate pathway in seaweeds
and can explain whether this pathway is conserved or seaweeds exhibit an entirely
different pathway from what is known in higher plants. Additionally, the active
forms of jasmonic acid such as methyl jasmonate or jasmonic acid isoleucine
conjugate or any other active forms can be identified and their mode of action can
be deduced in seaweeds. Therefore, lipid biochemistry is an extremely diverse
field with several unresolved questions in seaweeds, and systems biology
P. Kumari
seaweeds can only be explained with integrated systems biology approach of lipidomics, genomics, and proteomics.
Jasmonates are lipid-derived signal molecules belonging to oxylipin class that
mediates a plethora of biological processes from stress and defense responses to
reproductive development, secondary metabolism, and senescence in plants
(Browse 2009; Wasternack et al. 2012). They are generated via the allene oxide
synthase (AOS) branch of the lipoxygenase (LOX) pathway of lipid oxidation and
exert their effects by orchestrating large-scale reprogramming of gene expression
(Kombrink 2012). Methyl jasmonate (MeJA) is one of the most active forms of
jasmonic acid in plants produced by methyl ester formation on C1 of JA by
JA-specific methyltransferase (Seo et al. 2001). Numerous studies have implicated the roles of MeJA in defense against biotic/abiotic stresses in seaweeds
including C. crispus (Bouarab et al. 2004; Collén et al. 2013; Gaquerel et al.
2007), Fucus vesiculosus Linnaeus (Arnold et al. 2001), Laminaria digitata
(Hudson) J. V. Lamouroux (Küpper et al. 2009), and G. dura (Kumari et al. 2015).
However, it was unclear if MeJA was an endogenous compound in these seaweeds
until the recent report of MeJA release from the cystocarps of Grateloupia imbricata Holmes (Pilar et al. 2016). MeJA was earlier only detected in Gelidium latifolium Bornet ex Hauck (Krupina and Dathe 1991), and all other attempts to
detect MeJA in seaweeds (Chondrus, Colpomenia, Dictyota, Ectocarpus, Fucus,
Himanthalia, Saccharina, and Sargassum) were not successful (Bouarab et al.
2004; Wiesemeier et al. 2008). Further, adding to the complexity of MeJA pathway in seaweeds, the entire set of enzymes necessary for the biosynthesis of JA
from ALA has been identified in Gracilariopsis sp. (Hamberg and Gerwick 1993)
and Lithothamnion corallioides (P. Crouan & H. Crouan) P. Crouan & H. Crouan
(Hamberg 1992). The genome sequence of E. siliculosus (Cock et al. 2010) also
showed the candidate genes for AOS, which catalyzes the initial step of JA biosynthesis and allene oxide cyclase (AOC). On contrary, no candidate genes could
be identified for AOS and AOC in the genome of the red alga C. crispus, which
contained two candidate genes for 12-oxo-phytodienoic acid reductase (12-OPR)
and genes involved in ß-oxidation within the JA biosynthetic pathway (Collén
et al. 2013). Moreover, no genes for jasmonic acid carboxyl methyl transferase
have been identified in the genome of both the seaweeds indicating that an enzyme
different from those characterized in land plants may be present in these seaweeds
(Cock et al. 2010; Collén et al. 2013). No consensus is present in the scientific
community about the occurrence and physiological relevance of MeJA in seaweeds. The combined genomics, transcriptomics, proteomics, and lipidomics
study could only unveil the jasmonic acid/methyl jasmonate pathway in seaweeds
and can explain whether this pathway is conserved or seaweeds exhibit an entirely
different pathway from what is known in higher plants. Additionally, the active
forms of jasmonic acid such as methyl jasmonate or jasmonic acid isoleucine
conjugate or any other active forms can be identified and their mode of action can
be deduced in seaweeds. Therefore, lipid biochemistry is an extremely diverse
field with several unresolved questions in seaweeds, and systems biology
P. Kumari