84
phospholipid synthesis was also found to be dependent on phosphate availability,
while phosphate deprivation resulted in degradation of PLs to PA or lyso-phospholipids (Kumari et al. 2014b). Successively, Kumari et al. (2015) first time
reported polar lipidome of G. dura (C. Agardh) J. Agardh and of any seaweed
under methyl jasmonate stress using ESI-MS-based shotgun lipidomic approach,
highlighting the channeling of fatty acyl chains from MGDG toward the biosynthesis of 13-hydroperoxylinolenic acid, which further directed toward either the
jasmonate pathway or other alternative pathways of FA oxidation cascade, analogous to higher plants. These authors showed that MeJA induces a strong dose- and
time-dependent oxidative burst, resulting in lipid peroxidation, induction of fatty
acid oxidation cascade, hydroxy- oxylipin synthesis, upregulation of 13-LOX
pathway, and modulation of lipid acyl chains, along with a shift toward secondary
metabolism as a defense strategy to combat the induced oxidative stress. Lipid
molecular species belonging to MGDG, PC, PE, and PA were found to be differentially expressed lipid classes in response to MeJA treatment, of which MGDG
and PC were the most affected lipid classes due to higher metabolic flux of these
classes during lipid metabolism, as they are the primary sites for de novo fatty acid
allocation (Ohlrogge and Browse 1995). Also, high levels of PA (40:8, 40:7, 38:5,
38:4, 36:4, and 36:3) and lysolipids, LPC (20:4, 20:3, 18:3, and 18:2), and LPE
(20:4) were reported, which were probably generated from PC and PE in the
MeJA-treated thalli, indicating higher phospholipase activity and phospholipid
turnover in G. dura. Also, G. dura modulated the lipid acyl chains in such a way
that no significant change was observed in the fatty acid profile of the treated thalli
as compared with those of the control, except for C16:0, C16:1 (n-9), C20:3 (n-6),
and C20:4 (n-6) (P < 0.05). This may be a strategy to maintain the membrane fluidity and integrity of membrane to combat oxidative stress (Kumari et al. 2015).
Recently, Chen et al. (2016) employed UPLC-Q- TOF-MS and multivariate statistical analysis (PCA and heat maps) to decipher lipidomic changes of P. haitanensis in short-term response to high-temperature stress to understand the effect of
global warming on Pyropia sp. They identified 39 lipid biomarkers belonging to
the classes DAG, DGDG, lyso-MGDG, lyso-DGDG, SQDG, lyso-SQDG, lysoPA, lyso-PC, lyso- PE, lyso-PI, lyso-PG, and PIP differentially regulated in
response to high-temperature stress in Pyropia. The biomarker- based heat map
and box plots showed the decrease in levels of most of these lipid biomarkers (saccharolipids, Lyso-PE, Lyso-PI, Lyso-PG, and PIP) with the application of hightemperature stress (from 20 to 35 °C). This decrease in the level of major
photosynthetic membrane lipids due to heat stress was suggested to be a consequence of the impairment of its photosynthetic apparatus. The accumulation of PA
in plant cell membranes immediately after exposure to temperature stress concomitant with decrease in the levels of DAG, PE, and PG (Chen et al. 2016) indicated the transfer of the phosphatidyl group to produce PA (a stress biomarker).
These lipidomic alterations in P. haitanensis are significant for studies regarding
photosynthesis rate, signal transduction, and cell membrane stability during acclimation at higher temperature. In another study, UPLC-ESI-Q-TOF-MS analysisP. Kumari
phospholipid synthesis was also found to be dependent on phosphate availability,
while phosphate deprivation resulted in degradation of PLs to PA or lyso-phospholipids (Kumari et al. 2014b). Successively, Kumari et al. (2015) first time
reported polar lipidome of G. dura (C. Agardh) J. Agardh and of any seaweed
under methyl jasmonate stress using ESI-MS-based shotgun lipidomic approach,
highlighting the channeling of fatty acyl chains from MGDG toward the biosynthesis of 13-hydroperoxylinolenic acid, which further directed toward either the
jasmonate pathway or other alternative pathways of FA oxidation cascade, analogous to higher plants. These authors showed that MeJA induces a strong dose- and
time-dependent oxidative burst, resulting in lipid peroxidation, induction of fatty
acid oxidation cascade, hydroxy- oxylipin synthesis, upregulation of 13-LOX
pathway, and modulation of lipid acyl chains, along with a shift toward secondary
metabolism as a defense strategy to combat the induced oxidative stress. Lipid
molecular species belonging to MGDG, PC, PE, and PA were found to be differentially expressed lipid classes in response to MeJA treatment, of which MGDG
and PC were the most affected lipid classes due to higher metabolic flux of these
classes during lipid metabolism, as they are the primary sites for de novo fatty acid
allocation (Ohlrogge and Browse 1995). Also, high levels of PA (40:8, 40:7, 38:5,
38:4, 36:4, and 36:3) and lysolipids, LPC (20:4, 20:3, 18:3, and 18:2), and LPE
(20:4) were reported, which were probably generated from PC and PE in the
MeJA-treated thalli, indicating higher phospholipase activity and phospholipid
turnover in G. dura. Also, G. dura modulated the lipid acyl chains in such a way
that no significant change was observed in the fatty acid profile of the treated thalli
as compared with those of the control, except for C16:0, C16:1 (n-9), C20:3 (n-6),
and C20:4 (n-6) (P < 0.05). This may be a strategy to maintain the membrane fluidity and integrity of membrane to combat oxidative stress (Kumari et al. 2015).
Recently, Chen et al. (2016) employed UPLC-Q- TOF-MS and multivariate statistical analysis (PCA and heat maps) to decipher lipidomic changes of P. haitanensis in short-term response to high-temperature stress to understand the effect of
global warming on Pyropia sp. They identified 39 lipid biomarkers belonging to
the classes DAG, DGDG, lyso-MGDG, lyso-DGDG, SQDG, lyso-SQDG, lysoPA, lyso-PC, lyso- PE, lyso-PI, lyso-PG, and PIP differentially regulated in
response to high-temperature stress in Pyropia. The biomarker- based heat map
and box plots showed the decrease in levels of most of these lipid biomarkers (saccharolipids, Lyso-PE, Lyso-PI, Lyso-PG, and PIP) with the application of hightemperature stress (from 20 to 35 °C). This decrease in the level of major
photosynthetic membrane lipids due to heat stress was suggested to be a consequence of the impairment of its photosynthetic apparatus. The accumulation of PA
in plant cell membranes immediately after exposure to temperature stress concomitant with decrease in the levels of DAG, PE, and PG (Chen et al. 2016) indicated the transfer of the phosphatidyl group to produce PA (a stress biomarker).
These lipidomic alterations in P. haitanensis are significant for studies regarding
photosynthesis rate, signal transduction, and cell membrane stability during acclimation at higher temperature. In another study, UPLC-ESI-Q-TOF-MS analysisP. Kumari