Characterization of hsr201 and hsr515, two tobacco genes preferentially expressed during the hypersensitive reaction provoked by phytopathogenic bacteria

Abstract

During an incompatible interaction between tobacco and the bacterial phytopathogen Pseudomonas solanacearum, 2 classes of genes, the so-called hsr (hypersensitivity-related) genes, activated preferentially during the hypersensitive reaction, and the str (sensitivity-related) genes, expressed strongly during compatible and incompatible interactions, have been identified. In this report, two hsr cDNA clones, hsr515 and hsr201, as well as their expression patterns are presented. Hsr515 was found to encode a P450 monooxygenase and is most similar to the ripening-related avocado gene CYP71A1 (40.6% amino acid identity). Hsr201 presents 58.6% amino acid identity with pTom36, a tomato gene expressed during fruit maturation. The putative functions of the hsr gene products appear to be quite diverse and their characteristics of activation were found to be very conserved: accumulation of the corresponding mRNAs primarily in leaf areas in contact with the avirulent P. solanacearum strain or with a Pseudomonas fluorescens strain containing the hrpZ gene encoding a necrotizing polypeptide, harpin and absence of expression during normal plant development. Our results also suggest that, in a tobacco line expressing NahG, a lower level of salicylic acid, a compound associated with systemic acquired resistance, and also possibly involved in the development of necrotic lesions characteristic of the HR, does not affect the hsr gene expression.

Characterization of Maize Cytochrome P450 Monooxygenases Induced in Response to Safeners and Bacterial Pathogens

“…Of the five distinct P450 clones identified in this process, one clone (NA PCR 1) shared extremely close amino acid identity (93%) with the C terminus of the CYP71C3v1 sequence encoding the fourth hydroxylase in the DIMBOA biosynthetic pathway (Frey et al, 1997), substantial identity (61%-62%) with the second and third hydroxylases in this pathway and lesser identity (47%) with the first hydroxylase in the pathway. NA PCR 3 shared 70% to 71% amino acid identity with the tobacco CYP92A2 and CYP92A3 sequences (Czernic et al, 1996), 57% amino acid identity with the artichoke CYP76B1 sequence , and 42% amino acid identity with the maize CYP71C3 sequences (Frey et al, 1995;M.W. Persans, J.M.…”

Rapid and Transient Activation of a Myelin Basic Protein Kinase in Tobacco Leaves Treated with Harpin from Erwinia amylovora

“…Accumulation of SA is associated with systemic acquired resistance, a resistance response that occurs at a distance from the site of the HR (Ryals et al, 1996). Although treatment of plants with harpins leads to systemic acquired resistance (Strobel et al, 1996;Wei and Beer, 1996) no evidence that defense gene activation during harpininduced HR requires SA (Czernic et al, 1996). Molecular identification of HAPK will elucidate the possible relationship between HAPK and SA-induced PK.…”

A R2R3-MYB gene, AtMYB30 , acts as a positive regulator of the hypersensitive cell death program in plants in response to pathogen attack

“…Another way to elucidate the basis for the observed regulation of HR cell death by AtMYB30 is to examine the expression of genes that are either closely associated with HR, such as the hsr genes (13,26), or related to resistance, such as PR genes (27,28). For this purpose, we generated a cross between one of the tobacco sense lines (pBIM131-40A) and a reference line expressing a transcriptional fusion between the hsr203J promoter and the GUS reporter gene.…”

“…The expression of genes associated with HR cell death in tobacco, hsr203 and hsr515 (13,26), and Arabidopsis, Athsr3 (14), was examined by Northern blot analysis (Fig. 4 B and C).…”