Impact of transcriptional, ABA-dependent, and ABA-independent pathways on wounding regulation of RNS1 expression
Injured plants induce a wide range of genes whose products are thought to help to repair the plant or to defend against opportunistic pathogens that might infect the wounded plant. In Arabidopsis thaliana L., oligogalacturonides (OGAs) and jasmonic acid (JA) are the main regulators of the signaling pathways that control the local and systemic wound response, respectively. RNS1, a secreted ribonuclease, is induced by wounding in Arabidopsis independent of these two signals, thus indicating that another wound-response signal exists. Here we show that abscisic acid (ABA), which induces wound-responsive genes in other systems, also induces RNS1. In the absence of ABA signaling, wounding induces only approximately 45% of the endogenous levels of RNS1 mRNA. However, significant levels of RNS1 still accumulate in the absence of ABA signaling. Our results suggest that wound-responsive increases in ABA production may amplify induction of RNS1 by a novel ABA-independent pathway. To elucidate this novel pathway, we show here that the wound induction of RNS1 is due in part to transcriptional regulation by wounding and ABA. We also show evidence of post-transcriptional regulation which may contribute to the high levels of RNS1 transcript accumulation in response to wounding.
KeywordsAbscisic acid Post-transcriptional regulation Promoter Ribonuclease Wounding
Dehydration response element
The authors would like to thank Dr. Daniel Cook and Dr. Michael Thomashow (Michigan State University) for helpful discussions and for sharing ABA mutant seeds and the COR6.6 clone. We also thank Dr. Alan Myers (Iowa State University) for critical reading of the manuscript. This work was supported by the National Science Foundation (grant no. 0096394, 0228144, and 0445638 to P.J.G.), the US Department of Energy (grant no. DE-FG02-91ER20021 to P.J.G.), and the Roy J. Carver Charitable Foundation (grant no. 06-2323 to G.C.M.).
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