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Reference materials for quantitative determination of Cd, Cr, Hg and Pb in polycarbonate were developed. Reference materials with two concentration level of elements were prepared by adding appropriate amounts of chemicals to a blank polycarbonate base material. It was shown that ten bottles with triplicate analysis are enough to demonstrate the homogeneity of these candidate reference materials. The statistical results also showed no significant trends in both short-term stability test for four weeks and long-term stability test for twelve months. The certification of the four elements was carried out by isotope-dilution-inductively coupled plasma mass spectrometry (ID-ICP-MS) with microwave-assisted digestion. Certification of candidate reference materials in a single laboratory was confirmed with interlaboratory comparison participated by a certain number of well-recognized testing laboratories in Korea. The certified values and expanded uncertainties (k = 2) for the candidate reference material with low level and the one with high level were (51.7 ± 2.1) mg kg−1 Cd, (103.8 ± 2.9) mg kg−1 Cd, (98.8 ± 4.5) mg kg−1 Cr, (1004 ± 49.8) mg kg−1 Cr, (107.4 ± 4.6) mg kg−1 Hg, (1133 ± 50.7) mg kg−1 Hg, (94.8 ± 3.7) mg kg−1 Pb and (988.4 ± 53.6) mg kg−1 Pb, respectively. The reference materials developed in this study demonstrated their suitability for the quality assurance in Cd, Cr, Hg and Pb analysis for the implementation of RoHS Directive.

The yeast protein Dom34 is a key component of no-go decay, by which mRNAs with translational stalls are endonucleolytically cleaved and subsequently degraded. However, the identity of the endoribonuclease is unknown. Homologs of Dom34, called Pelota, are broadly conserved in eukaryotes and archaea. To gain insights into the structure and function of Dom34/Pelota, we have determined the structure of Pelota from Thermoplasma acidophilum (Ta Pelota) and investigated the ribonuclease activity of Dom34/Pelota. The structure of Ta Pelota is tripartite, and its domain 1 has the RNA-binding Sm fold. We have discovered that Ta Pelota has a ribonuclease activity and that its domain 1 is sufficient for the catalytic activity. We also demonstrate that domain 1 of Dom34 has an endoribonuclease activity against defined RNA substrates containing a stem loop, which supports a direct catalytic role of yeast Dom34 in no-go mRNA decay.

Plants constantly monitor environmental fluctuations to optimize their growth and metabolism. One example is adaptive growth occurring in response to biotic and abiotic stresses. Here, we demonstrate that GH3-mediated auxin homeostasis is an essential constituent of the complex network of auxin actions that regulates stress adaptation responses in Arabidopsis. Endogenous auxin pool is regulated, at least in part, through negative feedback by a group of auxin-inducible GH3 genes encoding auxin-conjugating enzymes. An Arabidopsis mutant, wes1-D, in which a GH3 gene WES1 is activated by nearby insertion of the (35)S enhancer, exhibited auxin-deficient traits, including reduced growth and altered leaf shape. Interestingly, WES1 is also induced by various stress conditions as well as by salicylic acid and abscisic acid. Accordingly, wes1-D was resistant to both biotic and abiotic stresses, and stress-responsive genes, such as pathogenesis-related genes and CBF genes, were upregulated in this mutant. In contrast, a T-DNA insertional mutant showed reduced stress resistance. We therefore propose that GH3-mediated growth suppression directs reallocation of metabolic resources to resistance establishment and represents the fitness costs of induced resistance.

Auxin functions, at least in part, by regulating a set of early auxin response genes: Aux/IAAs, GH3s and small auxin-up RNAs (SAURs). The SAUR genes encode short transcripts that accumulate rapidly after auxin treatment. There are 72 SAUR genes in Arabidopsis. However, none of these genes have been functionally characterized, although some members have been implicated in calcium/calmodulin-mediated auxin responses and etiolated seedling growth. Here, we investigated the function of a SAUR gene, abolished apical hook maintenance 1 (AAM1), through molecular genetic and transgenic studies. Transgenic Arabidopsis seedlings overexpressing AAM1 exhibited short, hookless hypocotyls with partially open cotyledons in darkness. The hookless phenotype was completely rescued by exogenous auxin. In contrast, hypocotyls of a T-DNA insertion mutant aam1 were slightly longer than wild-type hypocotyls and exhibited normal hook curvature. Notably, AAM1 is predominantly expressed on the inner side of the apical hook, similar to the DR5::GUS reporter. However, on illumination, the AAM1 transcripts were evenly distributed in the apical region, demonstrating that the apical hook development is intimately related to the localized expression of AAM1.