It appears that growth is inhibited with the concomitant degradation of the photosynthetic pigments and by a decrease in the photosynthetic capacity. Being an oxidative stress, we found an H2O2 burst within 15 min of menadione exposure, followed by an increase in antioxidant enzyme (superoxide dismutase [SOD], catalase [CAT], and ascorbate peroxidase [APX]) activities. In parallel, RT-PCR was performed for transcript check details analyses of Mn-SOD, CAT, and APX. Our results clearly revealed that expression of these genes were up-regulated upon menadione exposure. Furthermore, classical hallmarks of PCD such as
alteration of mitochondrial membrane potential, significant increase in caspase-3-like DEVDase activity, PI3K inhibitor cleavage of poly (ADP) ribose polymerase (PARP)-1-like enzyme, and DNA fragmentation as detected
by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) assay and oligosomal DNA fragmentation were observed. Moreover, antibodies against a mammalian active caspase-3 shared epitopes with a caspase-3-like protein of ~17 kDa; its pattern of expression and activity correlated with the onset of cell death. To the best of our knowledge, this is the first report on menadione-induced PCD through a mitochondrian-caspase protease pathway in an algal species. “
“Emiliania huxleyi (Lohmann) W. W. Hay et H. Mohler is a cosmopolitan coccolithophore species that forms massive blooms in low phosphorus seawater, partly due to its ability to utilize organic phosphate via extracellular alkaline phosphatase (AP). A novel AP gene, ehap1, was identified from the strain CCMP374. In this study, we examined the expression of ehap1 in various E. huxleyi strains and Lepirudin its genetic diversity in those strains and field populations. Two EHAP1 proteins (EHAP1a, 75 kDa and EHAP1b, 110 kDa) with virtually identical
sequence were expressed under P limitation in all strains except one; a third protein (EHAP1c, 115 kDa) was expressed in a few strains. The correlation between AP activity and protein abundance suggests that EHAP1b is inactive and probably the precursor of EHAP1a. The transcript of ehap1 was induced by P depletion in all strains. The ehap1 gene sequence is highly conserved in these strains and field populations with <3% nucleic acid substitution. Most of the ehap1 sequences from one site in the English Channel and three sites in the Gulf of Alaska were essentially identical to one another. No EHAP1-like protein can be detected in other phytoplankton species tested via Western blot analysis. The rapid induction and high activity of EHAP1 in E. huxleyi suggest that it plays a significant role in P regeneration in the oligotrophic ocean where E. huxleyi is abundant. The EHAP1 antibody and gene-specific primers are well suited to study the dynamics of P limitation in field populations of E. huxleyi.