@article{LeunertEckertPauletal.2014,
  author    = {Leunert, Franziska and Eckert, Werner and Paul, Andrea and Gerhardt, Volkmar and Grossart, Hans-Peter},
  title     = {Phytoplankton response to UV-generated hydrogen peroxide from natural organic matter},
  series = {Journal of plankton research},
  volume    = {36},
  journal   = {Journal of plankton research},
  number    = {1},
  publisher = {Oxford Univ. Press},
  address   = {Oxford},
  issn      = {0142-7873},
  doi       = {10.1093/plankt/fbt096},
  pages     = {185 -- 197},
  year      = {2014},
  abstract  = {In aquatic systems, natural organic matter (NOM) and in particular humic substances effectively absorb the ultraviolet (UV)/visible light spectrum of solar radiation and act as a photoprotective filter for organisms. Simultaneously, UV contributes to the generation of potentially harmful reactive oxygen species (ROS). Dose-response experiments were conducted on cyanobacteria and green algae with hydrogen peroxide (H2O2) as a long-lived representative of ROS. Delayed fluorescence (DF) decay kinetics was used as a non-invasive tool to follow changes of phytoplankton activity in real time. In order to investigate phototoxicity and photoprotection by NOM on phytoplankton, we exposed algae to UV-pre-irradiated NOM and direct UV excitation. Cyanobacteria responded to H2O2 concentrations as low as 10(-7) M, while green algae were 2 orders of magnitude less sensitive. UV irradiation of medium with NOM generated H2O2 concentrations of 1.5 x 10(-7) to 3.6 x 10(-7) M. When exposed to these concentrations, only the DF of cyanobacteria led to a measurable effect while that of green algae did not change. The addition of NOM protected all phytoplankton from direct UV irradiation, but cyanobacteria benefitted less. From this we conclude that UV-irradiated water enriched with NOM can adversely affect the physiology of cyanobacteria, but not of green algae, which might control phytoplankton composition and species-specific activities.},
  language  = {en}
}
@article{AlluSojaWuetal.2014,
  author    = {Allu, Annapurna Devi and Soja, Aleksandra Maria and Wu, Anhui and Szymanski, Jedrzej and Balazadeh, Salma},
  title     = {Salt stress and senescence: identification of cross-talk regulatory components},
  series = {Journal of experimental botany},
  volume    = {65},
  journal   = {Journal of experimental botany},
  number    = {14},
  publisher = {Oxford Univ. Press},
  address   = {Oxford},
  issn      = {0022-0957},
  doi       = {10.1093/jxb/eru173},
  pages     = {3993 -- 4008},
  year      = {2014},
  abstract  = {Leaf senescence is an active process with a pivotal impact on plant productivity. It results from extensive signalling cross-talk coordinating environmental factors with intrinsic age-related mechanisms. Although many studies have shown that leaf senescence is affected by a range of external parameters, knowledge about the regulatory systems that govern the interplay between developmental programmes and environmental stress is still vague. Salinity is one of the most important environmental stresses that promote leaf senescence and thus affect crop yield. Improving salt tolerance by avoiding or delaying senescence under stress will therefore play an important role in maintaining high agricultural productivity. Experimental evidence suggests that hydrogen peroxide (H2O2) functions as a common signalling molecule in both developmental and salt-induced leaf senescence. In this study, microarray-based gene expression profiling on Arabidopsis thaliana plants subjected to long-term salinity stress to induce leaf senescence was performed, together with co-expression network analysis for H2O2-responsive genes that are mutually up-regulated by salt induced-and developmental leaf senescence. Promoter analysis of tightly co-expressed genes led to the identification of seven cis-regulatory motifs, three of which were known previously, namely CACGTGT and AAGTCAA, which are associated with reactive oxygen species (ROS)-responsive genes, and CCGCGT, described as a stress-responsive regulatory motif, while the others, namely ACGCGGT, AGCMGNC, GMCACGT, and TCSTYGACG were not characterized previously. These motifs are proposed to be novel elements involved in the H2O2-mediated control of gene expression during salinity stress-triggered and developmental senescence, acting through upstream transcription factors that bind to these sites.},
  language  = {en}
}