salicylates and ethephon

Metallothioneins (MTs) are the cysteine-rich proteins with low molecular weight, which play important roles in maintaining intracellular ion homeostasis, detoxification of heavy metal ions and protecting against intracellular oxidative damages. In this study a novel ethephon-induced metallothionein gene, designated as HbMT2, was isolated and characterized from Hevea brasiliensis. The HbMT2 cDNA contained a 237 bp open reading frame encoding 78 amino acids and the deduced protein showed high similarity to the type 2 MTs from other plant species. Expression analysis revealed more significant accumulation of HbMT2 transcripts in leaves and latex than in roots and barks. The transcription of HbMT2 in latex was strongly induced by ethephon and hydrogen peroxide (H(2)O(2)) stress. Overproduction of recombinant HbMT2 protein gave the Escherichia coli cells more tolerance on Cu(2+) and Zn(2+), and the recombinant HbMT2 could scavenge the reactive oxidant species (ROS) in vitro. All these results indicated that HbMT2 could respond to ethephon stimulation and H(2)O(2) stress as a ROS scavenger in H. brasiliensis. It is also suggested that HbMT2 function in improving the tolerance of rubber trees to heavy metal ions, and repressing the ethephon-induced senilism and tapping panel dryness (TPD) development by ROS scavenge system in H. brasiliensis.

Topics: Amino Acid Sequence; Base Sequence; Copper; Electrophoresis, Polyacrylamide Gel; Escherichia coli; Free Radical Scavengers; Gene Expression Profiling; Gene Expression Regulation, Plant; Hevea; Hydrogen Peroxide; Hydroxyl Radical; Hydroxylation; Metallothionein; Molecular Sequence Data; Organophosphorus Compounds; Oxidants; Phylogeny; Plant Growth Regulators; Plant Proteins; Recombinant Proteins; Reverse Transcriptase Polymerase Chain Reaction; Salicylates; Sequence Homology, Amino Acid; Stress, Physiological; Zinc

We have isolated cDNA clones representing mRNAs encoding chitinase and 1,3-beta-glucanase in cotton (Gossypium hirsutum L.) leaves. The chitinase clones were sequenced and found to encode a 28,806 Da protein with 71% amino acid sequence similarity to the SK2 chitinase from potato (Solanum tuberosum). The 1,3-beta-glucanase clones encoded a 37,645 Da protein with 57.6% identity to a 1,3-beta-glucanase from soybean (Glycine max). Northern blot analyses showed that chitinase mRNA is induced in plants treated with ethaphon or salicylic acid, whereas the levels of 1,3-beta-glucanase mRNA are relatively unaffected. Southern blots of cotton genomic DNA and genomic clones indicated chitinase is encoded by a small gene family of which two members, Chi 2;1 and Chi 2;2, were characterized. These genes share 97% sequence identity in their transcribed regions. The genes were found to have three exons which are 309, 154 and 550 bp long, and two introns 99 and 154 bp in length. The 5'-flanking regions of Chi 2;1 and Chi 2;2 exhibit a large degree of similarity and may contain sequences important for gene response to chemical agents and fungal attack.

Topics: Amino Acid Sequence; Base Sequence; beta-Glucosidase; Chitinases; Cloning, Molecular; DNA, Complementary; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Plant; Genes, Plant; Glucan 1,3-beta-Glucosidase; Gossypium; Molecular Sequence Data; Organophosphorus Compounds; Plant Growth Regulators; Promoter Regions, Genetic; Restriction Mapping; RNA, Messenger; RNA, Plant; Salicylates; Salicylic Acid; Sequence Analysis, DNA; Sequence Homology, Amino Acid

To study the possible involvement of plant hormones in the synthesis of stress proteins in tomato upon inoculation with Cladosporium fulvum, we investigated the induction of mRNAs encoding PR proteins and ethylene biosynthesis enzymes by ethephon, 2,6-dichloroisonicotinic acid (INA) and salicylic acid (SA) by northern blot analysis. Ethephon slightly induced some but not all mRNAs encoding intra- and extracellular PR proteins. INA induced all PR protein mRNAs analysed, except for intracellular chitinase and extracellular PR-4. SA induced all PR protein mRNAs analyzed, except for intracellular chitinase and osmotin. None of the inducers affected the expression of ACC synthase mRNA, whereas all three induced ethylene-forming enzyme (EFE) mRNA.

Topics: Gene Expression; Isonicotinic Acids; Organophosphorus Compounds; Plant Growth Regulators; Plant Proteins; RNA, Messenger; Salicylates; Salicylic Acid; Solanum lycopersicum