02479nas a2200205   4500008004100000022001400041245013400055210006900189260001600258520174200274100002202016700002902038700002902067700001802096700001902114700002302133700002002156700002202176856007502198       2014                        eng d  a1460-243100aProgrammed cell death activated by Rose Bengal in Arabidopsis thaliana cell suspension cultures requires functional chloroplasts.0 aProgrammed cell death activated by Rose Bengal in Arabidopsis th  c2014 Apr 103 aLight-grown Arabidopsis thaliana cell suspension culture (ACSC) were subjected to mild photooxidative damage with Rose Bengal (RB) with the aim of gaining a better understanding of singlet oxygen-mediated defence responses in plants. Additionally, ACSC were treated with H2O2 at concentrations that induced comparable levels of protein oxidation damage. Under low to medium light conditions, both RB and H2O2 treatments activated transcriptional defence responses and inhibited photosynthetic activity, but they differed in that programmed cell death (PCD) was only observed in cells treated with RB. When dark-grown ACSC were subjected to RB in the light, PCD was suppressed, indicating that the singlet oxygen-mediated signalling pathway in ACSC requires functional chloroplasts. Analysis of up-regulated transcripts in light-grown ACSC, treated with RB in the light, showed that both singlet oxygen-responsive transcripts and transcripts with a key role in hormone-activated PCD (i.e. ethylene and jasmonic acid) were present. A co-regulation analysis proved that ACSC treated with RB exhibited higher correlation with the conditional fluorescence (flu) mutant than with other singlet oxygen-producing mutants or wild-type plants subjected to high light. However, there was no evidence for the up-regulation of EDS1, suggesting that activation of PCD was not associated with the EXECUTER- and EDS1-dependent signalling pathway described in the flu mutant. Indigo Carmine and Methylene Violet, two photosensitizers unable to enter chloroplasts, did not activate transcriptional defence responses in ACSC; however, whether this was due to their location or to their inherently low singlet oxygen quantum efficiencies was not determined.1 aGutiérrez, Jorge1 aGonzález-Pérez, Sergio1 aGarcia-Garcia, Francisco1 aDaly, Cara, T1 aLorenzo, Oscar1 aRevuelta, José, L1 aMcCabe, Paul, F1 aArellano, Juan, B  uhttp://jxb.oxfordjournals.org/content/early/2014/04/09/jxb.eru151.long