Implications of the Up-regulation of Genes Encoding Protein Degradation Enzymes and Heat Shock Protein 90 for Intertidal Green Macroalga Ulva fasciata Against Hypersalinity-Induced Protein Oxidation

Abstract

The molecular acclimation of intertidal green macroalga Ulva fasciata Delile to high salinity stress were examined by the construction of a forward cDNA library via the suppressive subtractive hybridization between 30‰ and 90‰ (24 h) and by the time course dynamics of several abundantly expressed genes. Among the genes with known sequences, the expressed sequence tags are abundant in the function of protein synthesis (ribosomal protein) and destination. The cDNAs of ATP-dependent Clp protease (UfClpC), 20S proteasome β-subunit type 1 domain (UfPbf1), ubiquitin-conjugating enzyme E2 I (UfUbc9), and heat shock protein 90A (UfHsp90A) were cloned. UfClpC transcript increased 3 h after 90‰ treatment, followed by a decrease, while UfPbf1 and UfUbc9 transcripts increased after 12 h and decreased at 48 h. The transcripts of UfHsp90A increased 1 h after 90‰ treatment, followed by a drop and to the control level at 48 h. Protease activity increased 3 h after 90‰ treatment and decreased to the control level at 48 h. H₂O₂ contents increased 1 h after 90‰ treatment and then remained unchanged, but protein carbonyl group contents increased after 48 h. The treatments of reactive oxygen species scavengers partially alleviated 90‰ damage (partial growth rescue) and suppressed the increases in H₂O₂ content, protein carbonyl group content, protease activity, and UfClpC, UfPbf1, UfUbc9, and UfHsp90A transcripts by 90‰. The induction of specific chaperones and proteases at the molecular level for protein quality control can be considered as one of the molecular mechanisms of hypersalinity acclimation in U. fasciata.

Polyamine effects on protein disulfide isomerase expression and implications for hypersalinity stress in the marine algaUlva lactucaLinnaeus1

“…The present results together with our previous study (Sung et al. ) have demonstrated that the acclimation of U . lactuca to hypersalinity stress could be partly achieved by the expression of genes related to protein destination and synthesis for the degradation of damaged and misfolded proteins and for the synthesis of proteins involved in the metabolic regulation and structural adjustment of functional properties.…”

“…lactuca (Sung et al. ). Not only the loss of damaged protein removal but also the loss of correct protein folding after prolonged hypersalinity treatment caused the recovery growth to decrease.…”

“…With this deficiency in mind, we have initiated a series of studies using Ulva lactuca Linnaeus (Chlorophyceae), an intertidal macroalga from the coastal waters of southern Taiwan, to understand mechanisms of acclimation to salinity stress at the molecular level. To date, we have found that oxidative stress occurs in this alga in response to hypersalinity (Lu et al 2006, Sung et al 2009), and several genes related to stress defenses and protein synthesis (ribosomal protein) and destination are markedly up-regulated by hypersalinity stress (Sung et al 2009(Sung et al , 2011a).…”

“…), and several genes related to stress defenses and protein synthesis (ribosomal protein) and destination are markedly up‐regulated by hypersalinity stress (Sung et al. , ,b).…”

“…lactuca thalli (24 h; Sung et al. ). Plant PDI or PDI‐like cDNA sequences have been cloned and sequenced from higher plants (Shorrosh and Dixon , , Chen and Hayes , Shimoni et al.…”