Phytochrome activates the plastid-encoded RNA polymerase for chloroplast biogenesis via nucleus-to-plastid signaling.

Light initiates chloroplast biogenesis by activating photosynthesis-associated genes encoded by not only the nuclear but also the plastidial genome, but how photoreceptors control plastidial gene expression remains enigmatic. Here we show that the photoactivation of phytochromes triggers the expression of photosynthesis-associated plastid-encoded genes (PhAPGs) by stimulating the assembly of the bacterial-type plastidial RNA polymerase (PEP) into a 1000-kDa complex. Using forward genetic approaches, we identified REGULATOR OF CHLOROPLAST BIOGENESIS (RCB) as a dual-targeted nuclear/plastidial phytochrome signaling component required for PEP assembly. Surprisingly, RCB controls PhAPG expression primarily from the nucleus by interacting with phytochromes and promoting their localization to photobodies for the degradation of the transcriptional regulators PIF1 and PIF3. RCB-dependent PIF degradation in the nucleus signals the plastids for PEP assembly and PhAPG expression. Thus, our findings reveal the framework of a nucleus-to-plastid anterograde signaling pathway by which phytochrome signaling in the nucleus controls plastidial transcription

NCP activates chloroplast transcription by controlling phytochrome-dependent dual nuclear and plastidial switches.

Phytochromes initiate chloroplast biogenesis by activating genes encoding the photosynthetic apparatus, including photosynthesis-associated plastid-encoded genes (PhAPGs). PhAPGs are transcribed by a bacterial-type RNA polymerase (PEP), but how phytochromes in the nucleus activate chloroplast gene expression remains enigmatic. We report here a forward genetic screen in Arabidopsis that identified NUCLEAR CONTROL OF PEP ACTIVITY (NCP) as a necessary component of phytochrome signaling for PhAPG activation. NCP is dual-targeted to plastids and the nucleus. While nuclear NCP mediates the degradation of two repressors of chloroplast biogenesis, PIF1 and PIF3, NCP in plastids promotes the assembly of the PEP complex for PhAPG transcription. NCP and its paralog RCB are non-catalytic thioredoxin-like proteins that diverged in seed plants to adopt nonredundant functions in phytochrome signaling. These results support a model in which phytochromes control PhAPG expression through light-dependent double nuclear and plastidial switches that are linked by evolutionarily conserved and dual-localized regulatory proteins

The Effect of Pretreatment with Thiopental on Reducing Pain Induced by Rocuronium Injection

We examined whether pretreatment with a small dose of thiopental was effective in reducing pain induced by the intravenous injection of rocuronium. Withdrawal movement was used to assess pain reduction. Ninety patients were randomly assigned to one of two groups: patients in the control group were pretreated with 2 mL saline, and those in the thiopental group were pretreated with 2 mL (50 mg) thiopental. Thiopental 5 mg/kg was injected intravenously. After a loss of consciousness, the upper arm was compressed with a rubber tourniquet, and the pretreatment drugs were administered. Thirty seconds later the tourniquet was removed and 0.6 mg/kg rocuronium was administered. Withdrawal movement was assessed using a four-grade scale: no movement, movement limited to the wrist, to the elbow or to the shoulder. The frequency of withdrawal movement in the group pretreated with thiopental was lower than in the control group (34 vs. 13, p < 0.05). We concluded that pretreatment with 2 mL (50 mg) thiopental is effective in reducing pain caused by the intravenous injection of rocuronium

Diplomirani studenti na Odsjeku za informacijske znanosti Filozofskog fakulteta Sveučilišta u Osijeku za razdoblje 2014.-2016.

<p><b>Copyright information:</b></p><p>Taken from "The SUMO E3 ligase, , regulates flowering by controlling a salicylic acid-mediated floral promotion pathway and through affects on chromatin structure"</p><p></p><p>The Plant Journal 2008;53(3):530-540.</p><p>Published online Jan 2008</p><p>PMCID:PMC2254019.</p><p>© 2007 The Authors Journal compilation 2007 Blackwell Publishing Ltd</p

Poplar GTL1 Is a Ca2+/Calmodulin-Binding Transcription Factor that Functions in Plant Water Use Efficiency and Drought Tolerance

Diminishing global fresh water availability has focused research to elucidate mechanisms of water use in poplar, an economically important species. A GT-2 family trihelix transcription factor that is a determinant of water use efficiency (WUE), PtaGTL1 (GT-2 like 1), was identified in Populus tremula × P. alba (clone 717-IB4). Like other GT-2 family members, PtaGTL1 contains both N- and C-terminal trihelix DNA binding domains. PtaGTL1 expression, driven by the Arabidopsis thaliana AtGTL1 promoter, suppressed the higher WUE and drought tolerance phenotypes of an Arabidopsis GTL1 loss-of-function mutation (gtl1-4). Genetic suppression of gtl1-4 was associated with increased stomatal density due to repression of Arabidopsis STOMATAL DENSITY AND DISTRIBUTION1 (AtSDD1), a negative regulator of stomatal development. Electrophoretic mobility shift assays (EMSA) indicated that a PtaGTL1 C-terminal DNA trihelix binding fragment (PtaGTL1-C) interacted with an AtSDD1 promoter fragment containing the GT3 box (GGTAAA), and this GT3 box was necessary for binding. PtaGTL1-C also interacted with a PtaSDD1 promoter fragment via the GT2 box (GGTAAT). PtaSDD1 encodes a protein with 60% primary sequence identity with AtSDD1. In vitro molecular interaction assays were used to determine that Ca2+-loaded calmodulin (CaM) binds to PtaGTL1-C, which was predicted to have a CaM-interaction domain in the first helix of the C-terminal trihelix DNA binding domain. These results indicate that, in Arabidopsis and poplar, GTL1 and SDD1 are fundamental components of stomatal lineage. In addition, PtaGTL1 is a Ca2+-CaM binding protein, which infers a mechanism by which environmental stimuli can induce Ca2+ signatures that would modulate stomatal development and regulate plant water use

The calcium/calmodulin-binding gtl1 transcription factor regulates stomatal development and plant water use

Calcium (Ca2+) and calmodulin (CaM) signaling has been implicated in the activation of plant adaptation and phenotypic plasticity responses to environmental stimuli, but little is known about the determinants and mechanisms that decode and transduce the Ca2+ signature. Arabidopsis thaliana GT2-LIKE 1 (GTL1) is a trihelix transcription factor that is a negative regulator of drought tolerance and water use efficiency (WUE), and a transcriptional repressor of STOMATAL DENSITY AND DISTRIBUTION (SDD1) that negatively regulates stomatal density. gtl1 loss-of-function T-DNA insertional mutations resulted in reduced stomatal density and transpiration, and improved drought tolerance and WUE, which was attributable to higher expression of SDD1. In vitro DNA-binding and in vivo chromatin-immunoprecipitation assays revealed that GTL1 directly binds to the GT3-box (GGTAAA) in the SDD1 promoter to repress expression. gtl1 constitutively induce SDD1 expression in plants, which is suppressed by GTL1 expression. Similarly, SDD1 expression was higher in gtl1-4 than in wild-type protoplasts and was suppressed by transient GTL1 expression. SDD1 expression was up-regulated by water-deficit or hyperosmotic stress, and induction was inhibited by Ca 2+ channel blockers gadolinium (Gd3+) and lanthanum (La3+) and the CaM antagonist W7, implicating the involvement of Ca2+/CaM signaling. In vitro assays determined that GTL1 binds CaM and the interaction is Ca2+ dependent, and H94 was identified as a CaM binding residue by site-specific mutation analysis. GTL1[H94E] prevented Ca2+/CaM binding while GTL1[H94Q] mutation that did not result in a residue charge difference did not abolish CaM binding. These results and in silico analysis indicated that the basic amphiphilic 2nd &agr;-helix (&agr;2 helix) of the N-terminal trihelix DNA-binding domain of GTL1 was necessary for CaM binding. GTL1 binds to the SDD1 promoter through the interaction with the GT3 cis-element located at -216 bp from the transcription start site. Ca2+/CaM inhibited the interaction between GTL1 and the SDD1 promoter, but did not affect binding of GTL1[H94E] to SDD1. Ca2+/CaM also dissociated GTL1 from the SDD1 promoter. Hyperosmotic stress induction of SDD1 expression was not suppressed by GTL1[H94E] as it was by GTL1. Together, these data support the notion that Ca2+/CaM binding to GTL1 prevents interaction of the transrepressor with the SDD1 promoter, which facilitates expression and negative regulation of stomatal development. This study links Ca2+ /CaM signaling directly to mechanisms that regulate transcription of a gene involved in the response to environmental stimuli