Transcriptional activation of 2 classes of genes during the hypersensitive reaction of tobacco leaves infiltrated with an incompatible isolate of the phytopathogenic bacterium Pseudomonas solanacearum

Abstract

Fourteen cDNA clones whose corresponding mRNAs accumulate during the hypersensitive reaction (HR) of tobacco leaves infiltrated with an incompatible strain of the bacterial pathogen Pseudomonas solanacearum have been subdivided by sequence homologies into 6 families. Studies on the accumulation of the mRNAs encoded by these genes in compatible and incompatible plant-bacterial interactions have been carried out and indicate that the 6 cDNA clones can be subdivided into 2 groups. In one group corresponding to 3 cDNA clones, the maximal level of mRNA accumulation is similar in both types of interaction, whereas in the other group, maximal mRNA accumulation in leaves undergoing an HR is 3- to 7-fold higher than in leaves infiltrated with the compatible strain. Within each group, the timing and kinetics of accumulation of the corresponding mRNAs differ for each individual cDNA clone. Run-on experiments indicate that transcriptional activation of these genes plays a major role in the control of their expression. Genomic hybridizations have been performed and indicate that the mRNAs corresponding to the cDNA clones are encoded by multigene families (6 to 20 genes).

Analysis and Effects of Cytosolic Free Calcium Increases in Response to Elicitors in Nicotiana plumbaginifolia Cells

“…The PAL (Phe ammonia-lyase) gene encodes a key enzyme of the phenylpropanoid biosynthetic pathway (Dixon, 2001), and hsr203J expression has been related to the hypersensitive response (Marco et al, 1990;Pontier et al, 1994). Assuming that the second sustained [Ca 2ϩ ] cyt increase, triggered by cryptogein but not by oligosaccharide elicitors, was a determinant for defense response expression and particularly the hypersensitive reaction, we compared the kinetics of accumulation of both gene transcripts in cryptogein-treated cell suspensions with and without lanthanum or BAPTA added after 10 min of cryptogein treatment and in OG-treated cells.…”

Nitrate Efflux Is an Essential Component of the Cryptogein Signaling Pathway Leading to Defense Responses and Hypersensitive Cell Death in Tobacco

“…Most of these transcripts accumulated during HR and correspond to different classes of so-called defense genes: genes encoding proteins with antioxidant properties (GST1a and GST1b) (Levine et al, 1994); hypersensitive-related (hsr) genes, including hsr515 and hsr203J, which encode proteins showing homology with cytochrome P450 and esterase, respectively (Marco et al, 1990;Pontier et al, 1994); sensitivityrelated (str) genes, including str319, which belongs to the sesquiterpene cyclase gene family (Keller et al, 1998); PAL, which encodes Phe ammonia-lyase, a key enzyme of the phenylpropanoid biosynthetic pathway (Dixon, 2001); PR-3 (pathogenesis-related), which encodes a basic chitinase (Fritig et al, 1998); and SAR8.2, which belongs to a 12-member gene family encoding small highly basic proteins of unknown function that are expressed during the HR and SAR (Alexander et al, 1992). We also investigated NpCaM-2, a calmodulin gene that remains expressed constitutively in response to wind and cold shock (Van Der Luit et al, 1999).…”

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

“…In the early steps of an incompatible interaction between tobacco and a bacterial pathogen, Pseudomonas solanacearum, at least two classes of plant genes are transcriptionally activated [32]. The hsr (hypersensitivity-related) genes are preferentially expressed during HR.…”