Constitutive Expressor of Pathogenesis-Related Genes5 affects cell wall biogenesis and trichome development

<p>Abstract</p> <p>Background</p> <p>The Arabidopsis thaliana <it>CONSTITUTIVE EXPRESSOR OF PATHOGENESIS-RELATED GENES5 </it>(<it>CPR5</it>) gene has been previously implicated in disease resistance, cell proliferation, cell death, and sugar sensing, and encodes a putative membrane protein of unknown biochemical function. Trichome development is also affected in <it>cpr5 </it>plants, which have leaf trichomes that are reduced in size and branch number.</p> <p>Results</p> <p>In the work presented here, the role of <it>CPR5 </it>in trichome development was examined. Trichomes on <it>cpr5 </it>mutants had reduced birefringence, suggesting a difference in cell wall structure between <it>cpr5 </it>and wild-type trichomes. Consistent with this, leaf cell walls of <it>cpr5 </it>plants contained significantly less paracrystalline cellulose and had an altered wall carbohydrate composition. We also found that the effects of <it>cpr5 </it>on trichome size and endoreplication of trichome nuclear DNA were epistatic to the effects of mutations in <it>triptychon </it>(<it>try</it>) or overexpression of <it>GLABRA3</it>, indicating that these trichome developmental regulators are dependant on <it>CPR5 </it>function for their effects on trichome expansion and endoreplication.</p> <p>Conclusion</p> <p>Our results suggest that <it>CPR5 </it>is unlikely to be a specific regulator of pathogen response pathways or senescence, but rather functions either in cell wall biogenesis or in multiple cell signaling or transcription response pathways.</p

MIDGET Unravels Functions of the Arabidopsis Topoisomerase VI Complex in DNA Endoreduplication, Chromatin Condensation, and Transcriptional Silencing[W]

The plant homologs of the archaeal DNA topoisomerase VI complex are required for the progression of endoreduplication cycles. Here, we describe the identification of MIDGET (MID) as a novel component of topoisomerase VI. We show that mid mutants show the same phenotype as rhl1, rhl2, and top6B mutants and that MID protein physically interacts with RHL1. The phenotypic analysis revealed new phenotypes, indicating that topoisomerase VI is involved in chromatin organization and transcriptional silencing. In addition, genetic evidence is provided suggesting that the ATR-dependent DNA damage repair checkpoint is activated in mid mutants, and CYCB1;1 is ectopically activated. Finally, we demonstrate that overexpression of CYCB1;2 can rescue the endoreduplication defects in mid mutants, suggesting that in mid mutants, a specific checkpoint is activated preventing further progression of endoreduplication cycles

High-Temperature Heat Capacity of Lanthanide Cuprates

Получены данные по теплоемкости La2Cu2O5 в интервале температур 354–877 К. По экспериментальным данным рассчитаны термодинамические функции твердого оксидного соединенияThis paper presents data on the heat capacity of lanthanide cuprates obtained in the temperature range 354 – 877 K. The thermodynamic functions of the solid oxide compound have been calculated using the experimental dat

AvrBsT Acetylates <i>Arabidopsis</i> ACIP1, a Protein that Associates with Microtubules and Is Required for Immunity

<div><p>Bacterial pathogens of plant and animals share a homologous group of virulence factors, referred to as the YopJ effector family, which are translocated by the type III secretion (T3S) system into host cells during infection. Recent work indicates that some of these effectors encode acetyltransferases that suppress host immunity. The YopJ-like protein AvrBsT is known to activate effector-triggered immunity (ETI) in <i>Arabidopsis thaliana</i> Pi-0 plants; however, the nature of its enzymatic activity and host target(s) has remained elusive. Here we report that AvrBsT possesses acetyltransferase activity and acetylates ACIP1 (for <i>ACETYLATED INTERACTING PROTEIN1</i>), an unknown protein from <i>Arabidopsis</i>. Genetic studies revealed that <i>Arabidopsis</i> ACIP family members are required for both pathogen-associated molecular pattern (PAMP)-triggered immunity and AvrBsT-triggered ETI during <i>Pseudomonas syringae</i> pathovar <i>tomato</i> DC3000 (Pst DC3000) infection. Microscopy studies revealed that ACIP1 is associated with punctae on the cell cortex and some of these punctae co-localize with microtubules. These structures were dramatically altered during infection. Pst DC3000 or Pst DC3000 AvrRpt2 infection triggered the formation of numerous, small ACIP1 punctae and rods. By contrast, Pst DC3000 AvrBsT infection primarily triggered the formation of large GFP-ACIP1 aggregates, in an acetyltransferase-dependent manner. Our data reveal that members of the ACIP family are new components of the defense machinery required for anti-bacterial immunity. They also suggest that AvrBsT-dependent acetylation <i>in planta</i> alters ACIP1's defense function, which is linked to the activation of ETI.</p></div

Mutation of K282 attenuates AvrBsT-triggered resistance.

<p>(A) Growth of Pst DC3000 in <i>Arabidopsis</i> Pi-0 leaves. Leaves were syringe infiltrated with a 1×10⁵ cells/mL suspension of bacteria: Pst DC3000 carrying vector (black bars), AvrBsT (white bars), AvrBsT(H154A) (dark grey bars) or AvrBsT(K282R) (light grey bars). Titers were assessed at 0 and 3 days post-inoculation. Data are mean cfu/cm² ± SD (n = 6). Asterisks indicate statistically significant differences from Pi-0 (student's <i>t</i>-test, **<i>p</i><0.01). Similar results were obtained in three independent experiments. (B) HR phenotypes in Pi-0 leaves. Leaves were infiltrated with a 3×10⁸ cells/mL suspension of Pst DC3000 carrying vector, AvrBsT or AvrBsT(K282R). Photograph was taken at 12 hours post-inoculation (HPI). Number of leaves exhibiting confluent HR at 10 HPI out of 18 inoculated leaves is shown at bottom.</p

Members of <i>Arabidopsis</i> ACIP family are required for AvrBsT-triggered ETI.

<p>(A) Increased growth of Pst DC3000 and Pst DC3000 AvrBsT in Pi-0 <i>ACIP</i> RNAi line #1 (red bars) and line #29 (blue bars) compared to wild-type Pi-0 (black bars). Leaves were syringe-infiltrated with a 1×10⁵ cells/mL suspension of bacteria. Titers were assessed at 0 and 3 days post-inoculation (DPI). Data are mean cfu/cm² ± SD (n = 4). Asterisks indicate statistically significant differences from Pi-0 (student <i>t</i>-test, *<i>p</i><0.05, **<i>p</i><0.01). Experiment was repeated three times with similar results. Inset: Immunoblot analysis of protein extracted from Pi-0 and Pi-0 <i>ACIP</i> RNAi leaves using anti-ACIP1 sera. Black dot, non-specific band (NS); arrowhead, detected ∼20 kDa protein band expected to correspond to ACIP1, ACIP-L1, and/or ACIP-L3. STD, molecular weight standard in kDa. Ponceau S-stained Rubisco large subunit was used as loading control. (B) AvrBsT-elicited HR phenotype in Pi-0 and Pi-0 <i>ACIP</i> RNAi lines. Leaves were infiltrated with a 3×10⁸ cells/mL suspension of Pst DC3000 alone (vector) or Pst DC3000 AvrBsT (AvrBsT). Photograph was taken at 9 hours post-inoculation (HPI). Number of leaves exhibiting confluent HR at 10 HPI out of 25 inoculated leaves is shown at right. (C) Quantification of electrolyte leakage in the leaves described in (B) at 10 HPI. Error bars represent SD (n = 10). Asterisks indicate statistically significant differences from Pi-0 (student's <i>t</i>-test, *p<0.05). Experiment was repeated three times with similar results.</p

AvrBsT is an acetyltransferase that specifically acetylates ACIP1.

<p>(A) AvrBsT auto-acetylation activity <i>in vitro</i>. Acetylation reactions using GST and GST-AvrBsT (wild-type, C222A, H154A, and K282R) proteins. (B) AvrBsT trans-acetylates ACIP1 <i>in vitro</i>. Acetylation reactions using GST-ACIP1 or GST with GST-AvrBsT, GST-AvrBsT(C222A), GST-AvrBT(H154A) or GST-AvrBsT(K282R). (C) Substrate specificity of AvrBsT and HopZ1a. Acetylation reactions using GST-ACIP1 or GST with GST-HopZ1a or GST-AvrBsT. For acetylation reactions, proteins were incubated with 0.4 µCi ¹⁴C-acetyl CoA and 100 nM inositol hexakisphosphate (IP₆) for 30 min at RT. Proteins were then separated by SDS-PAGE. Gels were stained with Coomassie and then analyzed by autoradiography. GST and GST-HopZ1a were used as negative and positive acetyltransferase enzyme controls, respectively. Acetylated proteins (GST-HopZ1a-^AC, GST-AvrBsT-^AC, and GST-ACIP1-^AC) are labeled in the autoradiograph. STD, molecular weight standard in kDa. GST = 28 kDa; GST-HopZ1a = 70 kDa; GST-AvrBsT = 65 kDa; GST-ACIP1 = 50 kDa. Similar results were obtained in three independent experiments.</p

Высокотемпературная теплоемкость купрата эрбия

Data on the molar heat capacity of Er2Cu2O5 (359 – 974 K) were obtained by differential scanning calorimetry. The Cp = f(T) experimental data were used to determine thermodynamic properties of this compoundМетодом дифференциальной сканирующей калориметрии получены экспериментальные данные по молярной теплоемкости Er2Cu2O5 (359–974 K). По экспериментальным данным Cp = f(T) рассчитаны термодинамические свойства оксидного соединени