An ERF/AP2-type transcription factor (CaPF1) was isolated by differential-display reverse transcription-PCR, following inoculation of the soybean pustule pathogen Xanthomonas axonopodis pv glycines 8ra, which induces hypersensitive response in pepper (Capsicum annuum) leaves. CaPF1 mRNA was induced under conditions of biotic and abiotic stress. Higher levels of CaPF1 transcripts were observed in disease-resistant tissue compared with susceptible tissue. CaPF1 expression was additionally induced using various treatment regimes, including ethephon, methyl jasmonate, and cold stress. To determine the role of CaPF1 in plants, transgenic Arabidopsis and tobacco (Nicotiana tabacum) plants expressing higher levels of CaPF1 were generated. Gene expression analyses of transgenic Arabidopsis and tobacco revealed that the CaPF1 level in transgenic plants affects expression of genes that contain either a GCC or a CRT/DRE box in their promoter regions. Furthermore, transgenic Arabidopsis plants expressing CaPF1 displayed tolerance against freezing temperatures and enhanced resistance to Pseudomonas syringae pv tomato DC3000. Disease tolerance was additionally observed in CaPF1 transgenic tobacco plants. The results collectively indicate that CaPF1 is an ERF/AP2 transcription factor in hot pepper plants that may play dual roles in response to biotic and abiotic stress in plants.

The first line of defense in plants against pathogens is induced by the recognition of microbe-associated molecular patterns (MAMP). Perception of bacterial flagellin (flg22) by the pattern recognition receptor flagellin-sensing 2 (FLS2) is the best characterized MAMP response, although the underlying molecular mechanisms are not fully understood. Here we studied the relationship between salicylic acid (SA) or jasmonic acid (JA) signaling and FLS2-mediated signaling by monitoring flg22-triggered responses in known SA or JA related mutants of Arabidopsis thaliana (L.) Heynh. The sid2 mutant, impaired in SA biosynthesis, had less basal FLS2 mRNA accumulation than the wild type, which correlated with suppression of early flg22 responses such as ROS production and induction of marker genes, WRKY29 and FRK1. The JA-signaling mutants, jar1 and coi1, exhibited an enhanced flg22-triggered oxidative burst and more callose accumulation than the wild type, and pretreatment with SA or coronatine (COR), a structural mimic of JA-isoleucine, altered these flg22-induced responses. Nonexpressor of pathogenesis-related genes 1 (NPR1) acted downstream of SID2 and required SA-dependent priming for the enhanced flg22-triggered oxidative burst and callose deposition. Activation of JA signaling by COR pretreatment suppressed the flg22-triggered oxidative burst and callose accumulation in a coronatine insensitive 1 (COI1) dependent manner. COR had a negative effect on flg22 responses but only the flg22-triggered oxidative burst depended on SA-JA/COR signaling antagonism. Thus the activated SA and JA signaling pathways have an influence on flg22-triggered oxidative burst and callose deposition. These results may explain how SA and JA signaling are cross talked for regulation of flg22-triggered responses.

Summary• Plants respond to pathogens by regulating a network of signaling pathways that fine-tune transcriptional activation of defense-related genes.• The aim of this study was to determine the role of Capsicum annuum WRKY zinc finger-domain transcription factor 1 (CaWRKY1) in defense. In previous studies, CaWRKY1 was found to be rapidly induced in C. annuum (chili pepper) leaves by incompatible and compatible pathogen inoculations, but the complexity of the network of the WRKY family prevented the function of CaWRKY1 in defense from being elucidated.• Virus-induced gene silencing of CaWRKY1 in chili pepper leaves resulted in decreased growth of Xanthomonas axonopodis pv. vesicatoria race 1. CaWRKY1-overexpressing transgenic plants showed accelerated hypersensitive cell death in response to infection with tobacco mosaic virus and Pseudomonas syringe pv. tabaci. Lower levels of pathogenesis-related gene induction were observed in CaWRKY1-overexpressing transgenic plants following salicylic acid (SA) treatments.• This work suggests that the newly characterized CaWRKY1, which is strongly induced by pathogen infections and the signal molecule SA, acts as a regulator to turn off systemic acquired resistance once the pathogen challenge has diminished and to prevent spurious activation of defense responses at suboptimal concentrations of SA.

New Ni-based bulk amorphous alloys in the alloy system Ni-Ti-Zr-(Si,Sn) were developed through systematic alloy design based upon the empirical rules for high glass forming alloys. Small additions of Si and/or Sn significantly improved the glass forming ability (GFA) of the alloys Ni 57 Ti 23−x Zr 20 (Si,Sn) x leading to a Ni-based bulk amorphous alloy. The amorphous ribbons of the alloys Ni 57 Ti 23−x Zr 20 (Si,Sn) x exhibited very high glass transition temperatures (T g > 823 K), crystallization temperatures (T x > 883 K), and large undercooled liquid regions (⌬T x > 50 K) implying the high GFA of the alloys. Fully amorphous rods with the diameter of up to 2 mm can be fabricated by a copper mold casting method. Development of the new Ni-based bulk amorphous alloys having high T g , T x , and ⌬T x expands the practical applications of amorphous alloys as structural materials.

We have isolated a full-length cDNA, PPI1 (pepper-PMMV interaction 1), encoding a novel basic region-leucine zipper (bZIP) DNA-binding protein, from expressed sequence tags differentially expressed in Capsicum chinense PI257284 infected with Pepper mild mottle virus (PMMV). PPI1 encodes a predicted protein of 170 amino acids and contains a putative DNA-binding domain that shares significant amino acid identity with ACGT-binding domains of members of the bZIP DNA-binding protein family. PPI1 was localized in the nucleus and had transcriptional activation activity in yeast. Transcripts of the PPI1 gene were preferentially induced during an incompatible interaction by inoculation with PMMV, Pseudomonas syringae pv. syringae 61, and Xanthomonas campestris pv. vesicatoria race 3. However, the PPI1 gene was not induced by abiotic stressors that activate the plant defense-signaling pathway. Our data provide the first evidence that a bZIP transcription factor is preferentially induced by pathogen attack, suggesting that PPI1 may play a specific functional role in the regulation of expression of plant defense-related genes.

Microstructural investigations on a series of (Ti70.5Fe29.5)100−xSnx alloys with x=5, 7, and 9 reveal that Sn addition is effective in introducing both structural and spatial heterogeneities in ultrafine eutectic composites stemming from a large temperature difference between two eutectic temperatures upon solidification. The microstructural heterogeneities in these ultrafine eutectic composites strongly enhance the room temperature compressive plasticity up to ∼15.7%.

Ductile Ti45Cu40Ni7.5Zr5Sn2.5 and Cu47.5Zr47.5Al5 bulk metallic glasses (BMGs) present different work hardening abilities under compression. Microstructural investigations reveal that nanoscale chemical heterogeneities occur throughout the samples. The morphology of the chemically heterogeneous domains in the as-cast Ti45Cu40Ni7.5Zr5Sn2.5 BMG is irregular and significantly interconnected. In contrast, the as-cast Cu47.5Zr47.5Al5 BMG exhibits a spherical morphology of the chemically heterogeneous regions. Furthermore, the distribution of the nanoscale chemical heterogeneity is macroscopically inhomogeneous throughout the material. These findings suggest that the different work hardening abilities of the Ti45Cu40Ni7.5Zr5Sn2.5 and Cu47.5Zr47.5Al5 BMGs possibly originate from the different morphologies and distributions of the chemically heterogeneous regions.

Summary• Plant receptor-like kinases belong to a large gene family. The Capsicum annuum receptor-like kinase 1 (CaRLK1) gene encodes a transmembrane protein with a cytoplasmic kinase domain and an extracellular domain.• The CaRLK1 extracellular domain (ECD)-green fluorescent protein (GFP) fusion protein was targeted to the plasma membrane, and the kinase domain of the CaRLK1 protein exhibited autophosphorylation activity. CaRLK1 transcripts were more strongly induced in treatment with Xag8ra than in treatment with Xag8-13. Furthermore, infection with incompatible Xanthomonas campestris pv. vesicatoria race 3 induced expression of CaRLK1 more strongly than in the compatible interaction.• Cell death caused by both a disease-forming and an HR-inducing pathogen was delayed in the CaRLK1-transgenic plants. Ectopic expression of CaRLK1 also induced transcripts of the lesion stimulating disease (LSD) gene, a negative regulator of cell death. Respiratory burst oxidase homolog (RBOH) genes were up-regulated in the transgenic plants compared with the wild type, as the concentration of the superoxide anion was increased. In contrast, the concentration of H 2 O 2 did not differ between the transgenic and wild-type plants.• These results support the theory that the suppression of plant cell death by CaRLK1 is associated with consistent production of the superoxide anion and induction of the RBOH genes and the LSD gene, but not with the concentration of H 2 O 2 . Thus, CaRLK1 may be a receptor of an as yet unidentified pathogen molecular pattern and may function as a negative regulator of plant cell death.