jasmonic-acid and endothall

With a specific focus on rice self-defense response(s), the effects of global signaling molecules, jasmonic acid (JA), salicylic acid (SA), abscisic acid (ABA), and ethylene (using the ethylene generator, ethephon), and protein phosphatase (PP) inhibitors, cantharidin and endothall on expression of a rice phospholipid hydroperoxide glutathione peroxidase (OsPHGPX) gene in rice seedling leaves were investigated. We provide first evidence for a potent up-regulation of the OsPHGPX mRNA accumulation by these signaling molecules and PP inhibitors that strongly suggest its potential role in defense/stress. The OsPHGPX gene also showed a weak constitutive expression and responsiveness to cut. These inductions were influenced by light signal(s), and did not show a requirement for de novo synthesized protein factor(s). A potential interaction amongst these signaling molecules, especially JA, SA, ABA and kinetin, in modulating the OsPHGPX expression was found. The blast pathogen, Magnaporthe grisea also elicited the accumulation of OsPHGPX mRNA in leaves. This is a first systematic report in rice (and in plants) demonstrating the inducible nature (and expression) of the OsPHGPX gene by a variety of defense/stress-related stimuli, and modulation by the PPs of the kinase-signaling cascade(s).

Topics: Abscisic Acid; Blotting, Northern; Cantharidin; Cyclopentanes; Dicarboxylic Acids; Dose-Response Relationship, Drug; Enzyme Inhibitors; Ethylenes; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Plant; Glutathione Peroxidase; Light; Magnaporthe; Organophosphorus Compounds; Oryza; Oxylipins; Phospholipid Hydroperoxide Glutathione Peroxidase; Phosphoprotein Phosphatases; Plant Growth Regulators; Plant Leaves; Plants; RNA, Messenger; Salicylic Acid; Staurosporine; Up-Regulation

The Bowman-Birk (BB) family of proteinase inhibitors (PI), initially reported from legume seeds, and thereafter also from wounded alfalfa and maize leaves appear to be regulated in similar ways as the extensively characterized PI I and PI II family from dicots. Here, we report a first characterization of the expression profiles of a rice (Oryza sativa L. cv. Nipponbare) BBPI gene, OsBBPI, which is part of a multigene family as demonstrated by genomic Southern hybridization. OsBBPI was found to be rapidly induced in rice seedling leaf in response to cut, exogenous jasmonic acid (JA), and two potent protein phosphatase 2A (PP2A) inhibitors, cantharidin (CN) and endothall (EN), in a light/dark-, time- and dose-dependent manner; this induction was completely inhibited by cycloheximide (CHX), indicating a requirement for de novo protein synthesis in its induction. Surprisingly, dark strongly up regulated cut-, JA-, CN-, and EN-induced OsBBPI expression, with the strongest enhancement observed with JA. A simultaneous application of a serine/threonine protein kinase inhibitor staurosporine (ST) did not affect significantly the JA-, CN-, and EN-induced OsBBPI transcript. Besides JA, it was found that the ethylene generator ethephon (ET) also had an enhancing effect on OsBBPI transcript, suggesting a direct effect of ethylene on OsBBPI expression. However, a simultaneous application of salicylic acid (SA) and abscisic acid (ABA), with JA, respectively, completely blocked OsBBPI gene expression, whereas kinetin (KN) was only partially effective. To the best of our knowledge, complete inhibition of JA-induced OsBBPI expression by SA is the first report in monocots, and with ABA in plants. Taken together, these results suggest that among the phytohormones tested here, JA and ethylene play important role(s) in regulating OsBBPI expression, with an intimate interaction with light signals. Finally, that the induced OsBBPI expression follows a kinase-signaling cascade is implied by the use of PP2A inhibitors.

Topics: Abscisic Acid; Amino Acid Sequence; Blotting, Southern; Cantharidin; Cyclopentanes; Darkness; Dicarboxylic Acids; DNA, Plant; Enzyme Inhibitors; Ethylenes; Gene Expression Regulation, Plant; Light; Models, Biological; Molecular Sequence Data; Organophosphorus Compounds; Oryza; Oxylipins; Phosphoprotein Phosphatases; Plant Leaves; Plant Proteins; Protein Phosphatase 2; RNA, Messenger; Salicylic Acid; Sequence Alignment; Sequence Homology, Amino Acid; Staurosporine; Stress, Mechanical; Trypsin Inhibitor, Bowman-Birk Soybean

A novel rice (Oryza sativa L.) gene, homologous to a sorghum pathogenesis-related class 10 protein gene, was cloned from a cDNA library prepared from 2-week-old jasmonic acid-treated rice seedling leaves, and named as JIOsPR10 (jasmonate inducible). JIOsPR10 encoded a 160-amino-acid polypeptide with a predicted molecular mass of 17,173.23 Da and a pI of 5.84. JIOsPR10 was highly similar (77%) to the sorghum PR10 protein, but showed less than 55% similarity with other identified PR10s at the amino acid level. Genomic Southern analyses indicated the presence of related genes in the rice genome. The JIOsPR10 transcript was not detected in the healthy leaves, and was not induced after cut. Further expression analysis revealed that the signaling components of defense/stress pathways, jasmonate, salicylate, and H(2)O(2) significantly up-regulated the JIOsPR10 mRNA over the cut control, whereas two other stress regulators, ethylene and abscisic acid, failed to induce its expression. Interestingly the protein phosphatase (PP) inhibitors, cantharidin, endothall, and okadaic acid, rapidly and potently up-regulated the JIOsPR10 expression, suggesting involvement of the phosphorylation/dephosphorylation events. Additionally, the inducible expression of the JIOsPR10 gene was influenced by light signal(s). Finally, the blast pathogen (Magnaporthe grisea) also specifically elicited the accumulation of JIOsPR10 mRNA in leaves. Induction of the JIOsPR10 gene expression by signaling molecules, PP inhibitors and pathogen attack, strongly indicate a role for this novel gene in rice self-defense/stress response(s).

Topics: Amino Acid Sequence; Base Sequence; Blotting, Northern; Blotting, Southern; Cantharidin; Cloning, Molecular; Cyclopentanes; Dicarboxylic Acids; DNA, Complementary; Enzyme Inhibitors; Gene Library; Genome, Plant; Hydrogen Peroxide; Molecular Sequence Data; Okadaic Acid; Oryza; Oxylipins; Peptides; Phosphoprotein Phosphatases; Phosphorylation; Phylogeny; Plant Leaves; Plant Proteins; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Salicylic Acid; Sequence Analysis, DNA; Sequence Homology, Amino Acid; Signal Transduction; Time Factors; Up-Regulation