ER Quality Control Components UGGT and STT3a Are Required for Activation of Defense Responses in <i>Bir1-1</i>

<div><p>The receptor-like kinase SUPPRESSOR OF BIR1, 1 (SOBIR1) functions as a critical regulator in plant immunity. It is required for activation of cell death and defense responses in Arabidopsis <i>bak1-interacting receptor-like kinase 1</i>,<i>1</i> (<i>bir1-1</i>) mutant plants. Here we report that the ER quality control component UDP-glucose:glycoprotein glucosyltransferase (UGGT) is required for the biogenesis of SOBIR1 and mutations in <i>UGGT</i> suppress the spontaneous cell death and constitutive defense responses in <i>bir1-1</i>. Loss of function of <i>STT3a</i>, which encodes a subunit of the oligosaccharyltransferase complex, also suppresses the autoimmune phenotype in <i>bir1-1</i>. However, it has no effect on the accumulation of SOBIR1, suggesting that additional signaling components other than SOBIR1 may be regulated by ER quality control. Our study provides clear evidence that ER quality control play critical roles in regulating defense activation in <i>bir1-1</i>.</p></div

Map- based cloning of <i>SOBIR6</i>.

<p>(A) Mapping of the <i>sobir6–1</i> mutation. Positions of the mapping markers, the gene structure of <i>SOBIR6</i> and the mutation site in <i>sobir6–1</i> are shown. The exons are indicated with boxes and introns with lines. The mutation site is located at the junction between the 29th intron and 30th exon. The lower case letters represent nucleotides in the intron and the uppercase letters represent nucleotides in the exon. (B) Morphology of <i>sobir6 bir1–1 pad4–1</i> alleles and representative F1 plants of indicated crosses for the complementation test. Plants were grown on soil at 23°C and photographed three weeks after planting. (C) Mutations identified in the <i>sobir6</i> alleles. aa, amino acid. ¹The positions of mutated nucleotide in the coding sequence are listed.</p

Accumulation of SOBIR1 protein in <i>sobir6–1</i> and <i>stt3a-2</i>.

<p>(A) Western blot analysis of SOBIR1-FLAG protein level (top) and RT-PCR analysis of <i>SOBIR1-FLAG</i> expression (bottom) in wild type (WT) and <i>sobir6–1</i> mutant background. (B)Western blot analysis of SOBIR1-FLAG protein level (top) and RT-PCR analysis of <i>SOBIR1-FLAG</i> expression (bottom) in WT and <i>stt3a-2</i> mutant background. Protein and RNA samples were extracted from 12-day-old seedlings grown on half-strength MS plates at 23°C. Rubisco was used as protein loading control and <i>ACTIN1</i> was used as RNA control.</p

Characterization of the <i>stt3a-2 bir1–1</i> double mutant.

<p>(A) Morphology of wild type (WT), <i>bir1–1</i> and <i>stt3a-2 bir1–1</i>. Plants were grown on soil at 23°C and photographed three weeks after planting. (B-C) Expression levels of <i>PR1</i> (B) and <i>PR2</i> (C) in WT, <i>bir1–1</i> and <i>stt3a-2 bir1–1</i> seedlings normalized by <i>ACTIN1</i>. Total RNA was extracted from 12-day-old seedlings grown on half-strength MS plates. (D) Growth of <i>H</i>. <i>a</i>. Noco2 on WT, <i>bir1–1</i> and <i>stt3a-2 bir1–1</i> seedlings. Error bars in (B-D) represent standard deviations of three measurements.</p

R² distribution in the entire SCNs population.

<p>256 and 182 fittings were implemented on regular and irregular SCNs separately. Most of R² of the fitting function calculated by NLSA with sinusoidal model aggregated within high value range (0.7–1.0). Furthermore, the R² in regular group was significantly higher than that in irregular group (<i>t</i>-test, <i>P</i> < 0.001).</p

Le Quart d'heure : gazette des gens demi-sérieux... / [rédigé par Valéry Vernier, A. Louvet, Zacharie Astruc]

20 mai 18591859/05/20 (T3,N7,A1)-1959/06/20 (T3,N9,A1)

Effects of stimulation on NLSA reliability.

<p>A (n = 30) and B (n = 20) exhibited the negative effect of frequency on the reliability for data analysis of regular and irregular SCNs separately. C (n = 18) and D (n = 18) showed the positive effect of amplitude on the reliability for data analysis of regular and irregular SCNs respectively.</p

Effect of discharge regularity on the reliability of NLSA (n = 98).

<p>R² of fitting function based on the data of neural response activity under constant SRS (frequency = 0.5 Hz, amplitude = 80 deg/s) as a function of CV*. The more regular the discharge regularity (quantified by CV*), the more reliable the NLSA.</p

IBR5 Modulates Temperature-Dependent, R Protein CHS3-Mediated Defense Responses in <i>Arabidopsis</i>

<div><p>Plant responses to low temperature are tightly associated with defense responses. We previously characterized the chilling-sensitive mutant <i>chs3-1</i> resulting from the activation of the Toll and interleukin 1 receptor-nucleotide binding-leucine-rich repeat (TIR-NB-LRR)-type resistance (R) protein harboring a C-terminal LIM (Lin-11, Isl-1 and Mec-3 domains) domain. Here we report the identification of a suppressor of <i>chs3</i>, <i>ibr5-7</i> (<i>indole-3-butyric acid response 5</i>), which largely suppresses chilling-activated defense responses. <i>IBR5</i> encodes a putative dual-specificity protein phosphatase. The accumulation of CHS3 protein at chilling temperatures is inhibited by the <i>IBR5</i> mutation. Moreover, <i>chs3</i>-conferred defense phenotypes were synergistically suppressed by mutations in <i>HSP90</i> and <i>IBR5</i>. Further analysis showed that IBR5, with holdase activity, physically associates with CHS3, HSP90 and SGT1b (Suppressor of the G2 allele of <i>skp1</i>) to form a complex that protects CHS3. In addition to the positive role of IBR5 in regulating CHS3, <i>IBR5</i> is also involved in defense responses mediated by <i>R</i> genes, including <i>SNC1</i> (<i>Suppressor of npr1-1</i>, <i>Constitutive 1</i>), <i>RPS4</i> (<i>Resistance to P</i>. <i>syringae 4</i>) and <i>RPM1</i> (<i>Resistance to Pseudomonas syringae pv</i>. <i>maculicola 1</i>). Thus, the results of the present study reveal a role for IBR5 in the regulation of multiple R protein-mediated defense responses.</p></div

<i>bHLH84</i>, <i>RSL2</i> and <i>RSL4</i> all exhibit dwarfism when overexpressed.

<p>A. Morphology of WT, three representative T1 transgenic plants of <i>35S:bHLH84</i> in Col-0, and <i>snc1.</i> B. Morphology of WT, two representative T1 transgenic plants of <i>35S:RSL2</i> in Col-0, and <i>snc1</i>. C. Morphology of WT, two representative T1 transgenic plants of <i>35S:RSL4</i> in Col-0, and <i>snc1</i>. All pictures were taken from four-week-old soil-grown plants.</p