ABSTRACT
NAC transcription factors are a family of functionally diverse proteins responsive to biotic and abiotic stresses. A full-length cDNA isolated from the salt stressed mangrove plant Avicennia marina showed high sequence identity to NAC proteins induced upon biotic stress in tomato and potato. The predicted protein sequence had all the highly conserved sub domains characteristic of NAC domain containing proteins. Northern analysis for AmNAC1 expression under tolerable (250 mM) concentration of NaCl revealed up regulation of the transcript after 48 h and higher transcript level after 10 days of treatment. Induction of AmNAC1 after 12h of ABA treatment was similar to the treatment with stressful (500 mM) concentration of NaCl. The results suggest the involvement of AmNAC1 in early salt stress response and long-term adjustment to salt, besides a role for ABA in its expression under salt stress conditions.
Subject(s)
Avicennia/metabolism , DNA, Complementary/genetics , RNA, Messenger/metabolism , Transcription Factors/genetics , Amino Acid Sequence , Avicennia/genetics , Base Sequence , DNA Primers , Molecular Sequence Data , RNA, Messenger/genetics , Sequence Homology, Amino Acid , Transcription Factors/chemistryABSTRACT
Plant photosynthesis results in the production of molecular oxygen. An inevitable consequence of this normal process is the production of reactive oxygen species (ROS) by the transfer of electrons to molecular oxygen. Plants are adequately protected by the presence of multiple antioxidative enzymes in different organelles of the plant such as chloroplasts, cytosol, mitochondria and peroxisomes. Under high light and CO(2) limiting conditions caused by environmental stress like salinity, these antioxidative enzymes play an important role in scavenging toxic radicals. To investigate the functions of antioxidative enzymes in a mangrove plant, we isolated three cDNAs encoding cytosolic Cu-Zn SOD (Sod1), catalase (Cat1) and ferritin (Fer1) from Avicennia marina cDNA library. Sod1, Cat1 and Fer1 cDNA encoded full-length proteins with 152, 492 and 261 amino acids respectively. We studied the expression of these antioxidant genes in response to salt, iron, hydrogen peroxide, mannitol and light stress by mRNA expression analysis. Cat1, Fer1 showed short-term induction while Sod1 transcript was found to be unaltered in response to NaCl stress. A decrease in mRNA levels was observed for Sod1, Cat1 while Fer1 mRNA levels remained unaltered with osmotic stress treatment. Sod1, Cat1 and Fer1 mRNA levels were induced by iron, light stress and by direct H(2)O(2) stress treatment, thus confirming their role in oxidative stress response.
Subject(s)
Antioxidants , Avicennia/genetics , Gene Expression Profiling , Genes, Plant/genetics , Iron/pharmacology , Light , Oxidative Stress/genetics , Sodium Chloride/pharmacology , Adaptation, Physiological/drug effects , Amino Acid Sequence , Antioxidants/metabolism , Avicennia/drug effects , Base Sequence , DNA, Complementary/genetics , DNA, Complementary/isolation & purification , Gene Expression Regulation, Plant/drug effects , Gene Expression Regulation, Plant/genetics , Hydrogen Peroxide/pharmacology , Mannitol/pharmacology , Models, Biological , Molecular Sequence Data , Osmotic Pressure/drug effects , Oxidative Stress/drug effects , Phenotype , Plant Proteins/chemistry , RNA, Messenger/genetics , RNA, Messenger/metabolismABSTRACT
Normal growth and development of plants is greatly dependent on the capacity to overcome environmental stresses. Environmental stress conditions like high salinity, drought, high incident light and low or high temperature cause major crop losses worldwide. A common denominator in all these adverse conditions is the production of reactive oxygen species (ROS) within different cellular compartments of the plant cell. Plants have developed robust mechanisms including enzymatic or nonenzymatic scavenging pathways to counter the deleterious effects of ROS production. There are a number of general reviews on oxidative stress in plants and few on the role of ROS scavengers during stress conditions. Here we review the regulation of antioxidant enzymes during salt stress in halophytes, especially mangroves. We conclude that (i) antioxidant enzymes protect halophytes from deleterious ROS production during salt stress, and (ii) genetic information from mangroves and other halophytes would be helpful in defining the roles of individual isoforms. This information would be critical in using the appropriate genes for oxidative stress defence for genetic engineering of enhanced stress tolerance in crop systems.
Subject(s)
Antioxidants/metabolism , Avicennia/metabolism , Oxidative Stress/physiology , Adaptation, Physiological/drug effects , Avicennia/drug effects , Avicennia/enzymology , Avicennia/genetics , Catalase/metabolism , Ferritins/metabolism , Genes, Plant , Oxidative Stress/drug effects , Oxidative Stress/genetics , Peroxidase/metabolism , Reactive Oxygen Species/metabolism , Sodium Chloride/pharmacology , Superoxide Dismutase/metabolismABSTRACT
Salinization poses an increasingly serious problem in coastal and agricultural areas with negative effects on plant productivity and yield. Avicennia marina is a pantropical mangrove species that can survive in highly saline conditions. As a first step towards the characterization of genes that contribute to combating salinity stress, the construction of a cDNA library of A. marina genes is reported here. Random expressed sequence tag (EST) sequencing of 1,841 clones produced 1,602 quality reads. These clones were classified into functional categories, and BLAST: comparisons revealed that 113 clones were homologous to genes earlier implicated in stress responses, of which the dehydrins are the most predominant in this category. Of the ESTs analyzed, 30% showed homology to previously uncharacterized genes in the public plant databases. Of these 30%, 52 clones were selected for reverse Northern analysis: 26 were shown to be up-regulated and five shown to be down-regulated. The results obtained by reverse Northern analysis were confirmed by Northern analysis for three clones.
