Immediate early transcription activation by salicylic acid via the cauliflower mosaic virus as-1 element.

Abstract

Transgenic tobacco plants carrying a number of regulatory sequences derived from the cauliflower mosaic virus 35s promoter were tested for their response to treatment with salicylic acid (SA), an endogenous signal involved in plant defense responses. PGlucuronidase (GUS) gene fusions with the full-length (-343 to +8) 35s promoter or the -90 truncation were found to be induced by SA. Time course experiments revealed that, in the continuous presence of SA, the -90 promoter construct (-90 35s-GOS) displayed rapid and transient induction kinetics, with maximum RNA levels at 1 to 4 hr, which declined to low levels by 24 hr. lnduction was still apparent in the presence of the protein synthesis inhibitor cycloheximide (CHX). Moreover, mRNA levels continued to accumulate over 24 hr rather than to decline. By contrast, mRNA from the endogenous pathogenesis-related protein-ia (PR-la) gene began to accumulate at later times during SA treatment and steadily increased thmugh 24 hr; transcription of this gene was almost completely blocked by the presence of CHX. Further dissection of the region from -90 and -46 of the 35s promoter revealed that the SAresponsive element corresponds to the previously characterized activation sequence-1 (as-í). These results represent a definitive analysis of immediate early responses to SA, relative to the late induction of PR genes, and potentially elucidate the early events of SA signal transduction during the plant defense response.

Salicylic acid (SA)‐dependent gene activation can be uncoupled from cell death‐mediated gene activation: the SA‐inducible NIMIN‐1 and NIMIN‐2 promoters, unlike the PR‐1a promoter, do not respond to cell death signals in tobacco

“…1B). This observation is consistent with previous analyses of PR‐1 gene expression, which occurs late after SA application (Qin et al ., 1994; Ward et al ., 1991). Similar results as for the NIMIN‐1[GUS] construct were obtained in time‐course experiments with the NIMIN‐2[GUS] chimeric gene (data not shown).…”

The identification and differential expression of Eucalyptus grandis pathogenesis-related genes in response to salicylic acid and methyl jasmonate

“…Elucidating the time dependent expression profiles of the putative orthologous signature genes under mock induction of the signaling pathways would provide a glimpse into how the genes would respond under pathogen conditions. SA hormone levels in tobacco plants infected with tobacco mosaic virus (Malamy et al, 1990, 1996) parallels the expression profile observed for EgrPR2 in this study (Figure 3A) under application of SA in E. grandis . In contrast to EgrPR2 , EgrPR5 was shown to gradually increase over the time points with a maximum expression level detected at 48 hpt (Figure 3B).…”

CPRF4a, a novel plant bZIP protein of the CPRF family: comparative analyses of light-dependent expression, post-transcriptional regulation, nuclear import and heterodimerisation

“…This result suggests that some compo-nents of signal transduction to the CHS promoter may be synthesised early after the onset of irradiation. CPRF mRNA accumulation is induced by CHX treatment in the dark, an observation which has also been reported for other transcription factors involved in hormone-, red light-, and salicylic acid-induced signalling (Lam et al 1989;Ballas et al 1993;Qin et al 1994;Jupin and Chua 1996). The rapid, transient expression of CPRFs, in combination with the CHX-inducible accumulation of their respective mRNAs, makes these transcription factors good candidates for early genes involved in UV light-mediated signalling.…”