Two homologous INDOLE-3-ACETAMIDE (IAM) HYDROLASE genes are required for the auxin effects of IAM in Arabidopsis

Indole-3-acetamide (IAM) is the first confirmed auxin biosynthetic intermediate in some plant pathogenic bacteria. Exogenously applied IAM or production of IAM by overexpressing the bacterial iaaM gene in Arabidopsis causes auxin overproduction phenotypes. However, it is still inconclusive whether plants use IAM as a key precursor for auxin biosynthesis. Herein, we reported the isolation IAM HYDROLASE 1 (IAMH1) gene in Arabidopsis from a forward genetic screen for IAM-insensitive mutants that display normal auxin sensitivities. IAMH1 has a close homolog named IAMH2 that is located right next to IAMH1 on chromosome IV in Arabidopsis. We generated iamh1 iamh2 double mutants using our CRISPR/Cas9 gene editing technology. We showed that disruption of the IAMH genes rendered Arabidopsis plants resistant to IAM treatments and also suppressed the iaaM overexpression phenotypes, suggesting that IAMH1 and IAMH2 are the main enzymes responsible for converting IAM into indole-3-acetic acid (IAA) in Arabidopsis. The iamh double mutants did not display obvious developmental defects, indicating that IAM does not play a major role in auxin biosynthesis under normal growth conditions. Our findings provide a solid foundation for clarifying the roles of IAM in auxin biosynthesis and plant development.     

Retinol oxidation to retinoic acid in human thyroid glandular cells

Abstract

Retinoic acid is regarded as the retinol metabolite that controls proliferation and differentiation of epithelial cells. In the present study, we investigated the potential role of xanthine dehydrogenase (XDH) in retinoic acid biosynthesis in human thyroid glandular cells (HTGC). In particular, we observed that cellular retinoids binding proteins (CRBPs) are also implicated in the biosynthetic pathway leading to retinoic acid formation in primary cultures of HTGC, as we have already reported for human mammary epithelial cells (HMEC). After partial protein purification, the enzyme responsible for retinoic acid biosynthesis was identified and quantified as XDH by immunoassay, by its ability to oxidize xanthine to uric acid and its sensitivity to the inhibitory effect of oxypurinol. The evidence of XDH-driven formation of retinoic acid in HTGC cultures further corroborates the potential role of XDH in retinoic acid biosynthesis in the epithelia.     

In Vivo Evidence for Serine Biosynthesis-Defined Sensitivity of Lung Metastasis,but Not of Primary Breast Tumors,to mTORC1 Inhibition

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Nontemplate Polymerization of Free Nucleotides Into Genetic Elements by Thermophilic DNA Polymerase in vitro

DNA synthesis is the cornerstone of all life forms and is required to replicate and restore the genetic information. Usually, DNA synthesis is carried out only by DNA polymerases semiconservatively to copy preexisting DNA templates. We report here that DNA strands were synthesized ab initio in the absence of any DNA or RNA template by thermophilic DNA polymerases at (a) a constant high temperature (74°C), (b) alternating temperatures (94°C/60°C/74°C), or (c) physiological temperatures (37°C). The majority of the ab initio synthesized DNA represented short sequence blocks, repeated sequences, intergenic spacers, and other unknown genetic elements. These results suggest that novel DNA elements could be synthesized in the absence of a nucleic acid template by thermophilic DNA polymerases in vitro. Biogenesis of genetic information by thermophilic DNA polymerase-mediated nontemplate DNA synthesis may explain the origin of genetic information and could serve as a new way of biosynthesis of genetic information that may have facilitated the evolution of life.

Supplemental materials are available for this article. Go to the publisher's online edition of Nucleosides, Nucleotides, and Nucleic Acids to view the free supplemental file.     

A New Acylated Anthocyanin from the Red Flowers of Camellia hongkongensis and Characterization of Anthocyanins in the Section Camellia Species

Twelve anthocyanins (1-12) were isolated from the red flowers of Camellia hongkongensis Seem. by chromatography using open columns. Their structures were elucidated on the basis of spectroscopic analyses, that is, proton-nuclear magnetic resonance, carbon 13-nuclear magnetic resonance, heteronuclear multiple quantum correlation, heteronuclear multiple bond correlation, high resolution electrospray ionization mass and ultraviolet visible spectroscopies. Out of these anthocyanins, a novel acylated anthocyanin, cyanidin 3-O-(6-O-(Z)-p-coumaroyl)-β-galactopyranoside (6), two known acylated anthocyanins, cyanidin 3-O-(6-O-(E)-p-coumaroyl)-β-galactopyranoside (7) and cyanidin 3-O-(6-O-(E)-caffeoyl)-β-galactopyranoside (8), and three known delphinidin glycosides (10-12) were for the first time isolated from the genus Camellia. Furthermore, pigment components in C. japonica L., C. chekiangoleosa Hu and C. semiserrata Chi were studied.The results indicated that the distribution of anthocyanins was differed among these species. Delphinidin glycoside was only detected in the flowers of C. hongkongensis, which is a special and important species in the section Camellia. Based on the characterization of anthocyanins in the section Camellia species, there is a close relationship among these species,and C. hongkongensis might be an important parent for creating new cultivars with bluish flower color.     

Occurrence of juvabione-type and epijuvabione-type sesquiterpenoids in Abies alba

The petrol-soluble fractions from the branchwood of four Abies alba trees were examined. Only two trees contained sufficient amounts of ‘juvabione-type’ insect juvenile hormone analogues for isolation and characterization. The first contained juvabione (4R, 1′R), 4′-dehydrojuvabione (4R, 1′R) and its 4R, 1′S diastereomer in a ratio of 3:1, and juvabiol (4R, 1′R, 3′S), isojuvabiol (4R, 1′R, 3′R) and epijuvabiol (4R, 1′S, 3′S) in an approximate ratio of 7:3:2. 4′-Dehydroepijuvabione (4R, 1′S) was the only ‘juvabione-type’ compound ioslated from the second tree. If it is accepted that juvabione and epijuvabione are enzymatically reduced forms of dehydrojuvabione and dehydroepijuvabione, respectively; then for these two A. alba our results indicate that only one enzyme which is specific for R chirality at C-1′ is present, since epijuvabione is not observed.