PCC1 : a merging point for pathogen defence and circadian signalling in Arabidopsis

Abstract

Using a cDNA-array we identified expressed sequence tag 163B24T7 as rapidly up-regulated in Arabidopsis thaliana (L.) Heynh. after pathogen exposure. Detailed expression analysis revealed that the corresponding gene is up-regulated not only after exposure to avirulent Pseudomonas syringae pv. tomato but also to virulent strains. This up-regulation is dependent on functional salicylic acid defence-signalling pathways. Moreover, we found the gene was circadian-regulated, showing peaks of expression at the end of the day. Using plants overexpressing the clock component CCA1, we showed that the PCC1 gene is regulated by the inner clock of Arabidopsis. Accordingly, we named the gene PCC1, for pathogen and circadian controlled. PCC1 is a member of a novel family of six small polypeptides in Arabidopsis. A functional role for PCC1 in plant defence was demonstrated since plants overexpressing PCC1 are resistant against normally virulent oomycetes. Thus, PCC1 demonstrates a potential interrelationship between pathogen and circadian signalling pathways.

Light Regulation and Daytime Dependency of Inducible Plant Defenses in Arabidopsis: Phytochrome Signaling Controls Systemic Acquired Resistance Rather Than Local Defense

“…It would thus be conceivable that the observed daytime-dependent differences in P. syringae-induced plant defenses result from the circadian rhythm. On the basis that some genes implicated in plant defense follow a circadian expression pattern, a link between defense and circadian signaling has been established previously (Sauerbrunn and Schlaich, 2004). Examples for such genes are Arabidopsis PCC1 (pathogen and circadian controlled 1) and PAL1 (Sauerbrunn and Schlaich, 2004;Rogers et al, 2005).…”

“…On the basis that some genes implicated in plant defense follow a circadian expression pattern, a link between defense and circadian signaling has been established previously (Sauerbrunn and Schlaich, 2004). Examples for such genes are Arabidopsis PCC1 (pathogen and circadian controlled 1) and PAL1 (Sauerbrunn and Schlaich, 2004;Rogers et al, 2005). The plant circadian clock maintains a relatively constant period, even in the absence of environmental cues such as light (Hotta et al, 2007).…”

“…Because pathogen defense has previously been linked with the circadian rhythm (Sauerbrunn and Schlaich, 2004), we examined a possible contribution of the circadian clock to the observed daytime effect on SA accumulation. Conventionally grown plants were therefore placed into continuous darkness from dusk of day 21 (the day before the pathogen experiment was started), and leaves were inoculated with Psm avrRpm1 the following day (day 0) at 9 AM or at 7 PM (Fig.…”

Arabidopsis Defense against Botrytis cinerea: Chronology and Regulation Deciphered by High-Resolution Temporal Transcriptomic Analysis

“…However, a small polypeptide PCC1, whose overexpression leads to resistance against Hyaloperonospora arabidopsidis, is under both defense and circadian regulation (Sauerbrunn and Schlaich, 2004), and, recently, a group of genes involved in basal and R-mediated defense was shown to be under the control of CCA1, a core clock component . In the latter study, the central clock oscillator appeared unaffected by H. arabidopsidis infection.…”

Lights, Rhythms, Infection: The Role of Light and the Circadian Clock in Determining the Outcome of Plant–Pathogen Interactions

“…Does this anticipation by the plant of regular abiotic environmental changes extend to anticipation of changes in biotic challenges? Certainly pathogen-inducible genes have been identified that have diurnal and/or circadian rhythms of expression (Molina et al, 1997;Wang et al, 2001;Sauerbrunn and Schlaich, 2004;Weyman et al, 2006). The functional significance of this is not yet clear, as it was also recently demonstrated that under defined environmental conditions, 89% of Arabidopsis transcripts are expressed rhythmically, being regulated by the circadian clock or directly by environmental changes in light or temperature (Michael et al, 2008).…”