Strigolactones (SLs) stimulate seed germination of root parasitic plants and induce hyphal branching of arbuscular mycorrhizal fungi in the rhizosphere. In addition, they have been classified as a new group of plant hormones essential for shoot branching inhibition. It has been demonstrated thus far that SLs are derived from carotenoid via a biosynthetic precursor carlactone (CL), which is produced by sequential reactions of DWARF27 (D27) enzyme and two carotenoid cleavage dioxygenases CCD7 and CCD8. We previously found an extreme accumulation of CL in the more axillary growth1 (max1) mutant of Arabidopsis, which exhibits increased lateral inflorescences due to SL deficiency, indicating that CL is a probable substrate for MAX1 (CYP711A1), a cytochrome P450 monooxygenase. To elucidate the enzymatic function of MAX1 in SL biosynthesis, we incubated CL with a recombinant MAX1 protein expressed in yeast microsomes. MAX1 catalyzed consecutive oxidations at C-19 of CL to convert the C-19 methyl group into carboxylic acid, 9-desmethyl-9-carboxy-CL [designated as carlactonoic acid (CLA)]. We also identified endogenous CLA and its methyl ester [methyl carlactonoate (MeCLA)] in Arabidopsis plants using LC-MS/MS. Although an exogenous application of either CLA or MeCLA suppressed the growth of lateral inflorescences of the max1 mutant, MeCLA, but not CLA, interacted with Arabidopsis thaliana DWARF14 (AtD14) protein, a putative SL receptor, as shown by differential scanning fluorimetry and hydrolysis activity tests. These results indicate that not only known SLs but also MeCLA are biologically active in inhibiting shoot branching in Arabidopsis.strigolactone | biosynthesis | cytochrome P450 | Arabidopsis | rice S trigolactones (SLs) are allelochemicals, exuded from plant roots, that stimulate seed germination of root parasitic plants, Striga spp., Orobanche spp., and Phelipanche spp. (1). The hyphal branching of the biotrophic arbuscular mycorrhizal (AM) fungi is also induced by SLs in the vicinity of host roots to ensure symbiosis with host plants (2). SLs are not only host recognition signals in the rhizosphere but also play important roles in the SLproducing plants themselves. Since the mid-1990s, the existence of novel hormone-like signals involved in shoot branching inhibition of plants had been proposed following the isolation and analysis of mutants with increased shoot branching, ramosus (rms) of pea (Pisum sativum), decreased apical dominance (dad) of petunia (Petunia hybrida), more axillary growth (max) of Arabidopsis (Arabidopsis thaliana), and dwarf (d) and high tillering dwarf (htd) of rice (Oryza sativa) (3-6). Recently, these mutants have been identified as SL-deficient or -insensitive mutants, providing decisive evidence that SLs function as shoot branchinhibiting hormones (7,8). In addition, further characterization of these mutants has shown that SLs affect root growth and development, leaf shape and senescence, internode elongation, secondary growth, and drought and salinity stress responses (9-11).Despit...

The gene responsible for DNFB1 and DFNA3, connexin 26 (GJB2), was recently identified and more than 20 disease causing mutations have been reported so far. This paper presents mutation analysis for GJB2 in Japanese non-syndromic hearing loss patients compatible with recessive inheritance. It was confirmed that GJB2 mutations are an important cause of hearing loss in this population, with three mutations, 235delC, Y136X, and R143W, especially frequent. Of these three mutations, 235delC was most prevalent at 73%. Surprisingly, the 35delG mutation, which is the most common GJB2 mutation in white subjects, was not found in the present study. Our data indicated that specific combinations of GJB2 mutation exist in diVerent populations. (J Med Genet 2000;37:41-43)

Molecular diagnosis makes a substantial contribution to precise diagnosis, subclassification, prognosis, and selection of therapy. Mutations in the PDS (SLC26A4) gene are known to be responsible for both Pendred syndrome and nonsyndromic hearing loss associated with enlarged vestibular aqueduct, and the molecular confirmation of the PDS gene has become important in the diagnosis of these conditions. In the present study, PDS mutation analysis confirmed that PDS mutations were present and significantly responsible in 90% of Pendred families, and in 78.1% of families with nonsyndromic hearing loss associated with enlarged vestibular aqueduct. Furthermore, variable phenotypic expression by the same combination of mutations indicated that these two conditions are part of a continuous category of disease. Interestingly, the PDS mutation spectrum in Japanese, including the seven novel mutations revealed by this study, is very different from that found in Caucasians. Of the novel mutations detected, 53% were the H723R mutation, suggesting a possible founder effect. Ethnic background is therefore presumably important and should be noted when genetic testing is being performed. The PDS gene mutation spectrum in Japanese may be representative of those in Eastern Asian populations and its elucidation is expected to facilitate the molecular diagnosis of a variety of diseases.

Enlarged vestibular aqueduct (EVA), known as the most common form of inner ear abnormality, has recently been of particular genetic interest because this anomaly is inherited in a recessive manner. The locus for non-syndromic sensorineural hearing loss with EVA has been mapped to the same chromosomal region, 7q31, as the Pendred syndrome locus. In the present study, seven mutations in the PDS gene (PDS), the gene responsible for Pendred syndrome, have been found in families of non-syndromic sensorineural hearing loss with EVA. One family is homozygous, three families are compound heterozygotes, and two families are heterozygous but with no other mutation detected. The present results provide evidence that mutations in PDS cause both syndromic and non-syndromic hearing loss.

In an attempt to clarify conflicting published data, we report new measurements of specific heat, resistivity, magnetic susceptibility, and thermal expansivity up to room temperature for the 6 K superconductor ZrB 12 , using well-characterized single crystals with a residual resistivity ratio Ͼ9. The specific heat gives the bulk result 2⌬͑0͒ / k B T c = 3.7 for the superconducting gap ratio, and excludes multiple gaps and d-wave symmetry for the Cooper pairs. The Sommerfeld constant ␥ n = 0.34 mJ K −2 gat −1 and the magnetic susceptibility = −2.1 ϫ 10 −5 indicate a low density of states at the Fermi level. The Debye temperature D is in the range 1000-1200 K near zero and room temperature, but decreases by a factor of ϳ2 at ϳ35 K. The specific heat and resistivity curves are inverted to yield approximations of the phonon density of states F͑͒ and the spectral electron-phonon scattering function ␣ tr 2 F͑͒, respectively. Both unveil a 15 meV mode, attributed to Zr vibrations in oversized B cages, which gives rise to electron-phonon coupling. The thermal expansivity further shows that this mode is anharmonic, while the vanishingly small discontinuity at T c establishes that the cell volume is nearly optimal with respect to T c .