Strigolactones (SLs) are a class of plant hormones which regulate shoot branching and function as host recognition signals for symbionts and parasites in the rhizosphere. However, steps in SL biosynthesis after carlactone (CL) formation remain elusive. This study elucidated the common and diverse functions of MAX1 homologs which catalyze CL oxidation. We have reported previously that ArabidopsisMAX1 converts CL to carlactonoic acid (CLA), whereas a rice MAX1 homolog has been shown to catalyze the conversion of CL to 4-deoxyorobanchol (4DO). To determine which reaction is conserved in the plant kingdom, we investigated the enzymatic function of MAX1 homologs in Arabidopsis, rice, maize, tomato, poplar and Selaginella moellendorffii. The conversion of CL to CLA was found to be a common reaction catalyzed by MAX1 homologs, and MAX1s can be classified into three types: A1-type, converting CL to CLA; A2-type, converting CL to 4DO via CLA; and A3-type, converting CL to CLA and 4DO to orobanchol. CLA was detected in root exudates from poplar and Selaginella, but not ubiquitously in other plants examined in this study, suggesting its role as a species-specific signal in the rhizosphere. This study provides new insights into the roles of MAX1 in endogenous and rhizosphere signaling.

Penicillin G, novobiocin, bacitracin, and enduracidin were used for selection of supersensitive mutants. This paper mainly reports results on novobiocin-supersensitive (NS) mutants. Most of these mutants were found to have defective lipopolysaccharides (LPS). The role of LPS in the adsorption of phages on E. coli was also studied. MATERIALS AND METHODS Bacteria and isolation of antibiotic-supersensitive mutants. Mutants were isolated from E. coli K-12 strain JEIOI I (F-thrleutrp-his-thythiara-lacgalxyl-mtlstr). (Genetic symbols are defined in Fig. 1.) Bacteria were usually cultured in nutrient broth at 37 C with shaking. Nutrient broth contained (per liter of deionized water): polypeptone (Daigo Eiyo Kagaku Co., Osaka, Japan), 10 g; Ehrlich meat extract (Kyokuto Seiyaku Co., Tokyo, Japan), 10 g; and NaCl, 2 g. It was adjusted to pH 7.4 by addition of I ml of 10 N NaOH per liter. For nutrient agar, nutrient broth was solidified by addition of 1.5% agar (Wako Pure Chemical Co., Osaka, Japan). Cells were treated with N-methyl-N'-nitro-N-nitrosoguanidine (NTG) essentially by the method of Adelberg et al. (1). Cells in the logarithmic phase of growth (5 ml of culture) were collected by centrifugation, 968

The adsorption state of 1,4-cyclohexadiene on a Si(100)(2×1) surface is studied with synchrotron radiation photoelectron spectroscopy (PES), high-resolution electron energy loss spectroscopy (HREELS), and scanning tunneling microscopy (STM). The existence of one π bond in the chemisorbed 1,4-cyclohexadiene is confirmed by valence band PES and HREELS measurements. The bonds between the 1,4-cyclohexadiene molecule and Si surface are characterized by the observation of a Si-C stretching mode in HREEL spectra and the interface component due to the Si-C bond in high-resolution Si 2p spectra. The remaining outermost π states in the adsorbed molecule are observed directly in the STM images. From HREELS and PES results, it is also clarified that the chemisorption state is basically invariable at any coverage. † Part of the special issue "John T. Yates, Jr. Festschrift".

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The phylogenetic relationships of all 16 genera (plus Psenes pellucidus) of the suborder Stromateoidei were estimated cladistically based on 43 osteological, myological, and external characters. Thirty equally parsimonious trees were obtained. Based on the strict consensus tree, Centrolophidae was nonmonophyletic, Psenopsis being placed as a sister group of a clade comprising Amarsipus, Ariomma, nomeids, Tetragonurus, and stromateids. Schedophilus formed a sister group relationship with Seriolella. The relationships among the Centrolophus, Hyperoglyphe, Icichthys, Tubbia, Schedophilus ϩ Seriolella clade, and Psenopsis ϩ Amarsipus ϩ Ariomma ϩ nomeids ϩ Tetragonurus ϩ stromateids clade were unresolved. Amarsipus, which is unique within the suborder in lacking a pharyngeal sac, was nested within the stromateoid clade, being a sister group of the clade including Ariomma, nomeids, Tetragonurus, and stromateids. The absence of a pharyngeal sac in Amarsipus was interpreted as a reversal, its presence in the Stromateoidei therefore being considered as a synapomorphy. Ariomma was placed as the sister group of a clade comprising nomeids, Tetragonurus, and stromateids. Monophyly of the Nomeidae and Stromateidae were supported by 2 and 11 synapomorphies, respectively.