During differentiation, the Arabidopsis (Arabidopsis thaliana) seed coat epidermal cells secrete mucilage composed primarily of rhamnogalacturonan I that is extruded from the seed coat upon imbibition. The mucilage of the mucilage modified1 (mum1) mutant contains rhamnogalacturonan I that is more highly branched and lacks the ability to be extruded when exposed to water. Our cloning of the MUM1 gene shows that it encodes a putative transcription factor, LEUNIG_HOMOLOG (LUH). Cellular localization and transcriptional assay results suggest that LUH/MUM1 is a nucleus-localized transcriptional activator. LUH/MUM1 is expressed in all the tissues examined, including the seed coat. Quantitative reverse transcription-polymerase chain reaction data suggest that LUH/MUM1 is expressed throughout seed coat development, reaching peak expression late in differentiation. LUH1/MUM1 expression in plants homozygous for mutations in several genes encoding regulators of seed coat mucilage was unchanged. Thus, LUH/MUM1 expression appears to be independent of other transcription factors known to regulate aspects of seed coat mucilage biology. The expression in the luh/mum1 mutant of three genes encoding enzymes needed for mucilage extrusion, MUM2, SUBSILIN PROTEASE1.7, and b-XYLOSIDASE1, was reduced relative to that of the wild type. Overexpression of MUM2 could partially rescue the mum1 phenotype. These data suggest that LUH/MUM1 is a positive regulator of all three genes.

Strain SPC-1 T was isolated from the phyllosphere of Cynara cardunculus L. var. sylvestris (Lamk)Fiori (wild cardoon), a Mediterranean native plant considered to be the wild ancestor of the globe artichoke and cultivated cardoon. This Gram-stain-negative, catalase-positive, oxidase-negative, non-spore-forming, rod-shaped and non-motile strain secreted copious amounts of an exopolysaccharide, formed slimy, viscous, orange-pigmented colonies and grew optimally at around pH 6.0-6.5 and 26-30 6C in the presence of 0-0.5 % NaCl. Phylogenetic analysis based on comparisons of 16S rRNA gene sequences demonstrated that SPC-1 T clustered together with species of the genus Sphingomonas sensu stricto. The G+C content of the DNA (66.1 mol%), the presence of Q-10 as the predominant ubiquinone, sym-homospermidine as the predominant polyamine, 2-hydroxymyristic acid (C 14 : 0 2-OH) as the major hydroxylated fatty acid, the absence of 3-hydroxy fatty acids and the presence of sphingoglycolipid supported this taxonomic position. 16S rRNA gene sequence analysis showed that SPC-1 T was most closely related to Sphingomonas hankookensis ODN7 T , Sphingomonas insulae DS-28 T andSphingomonas panni C52 T (98.19, 97.91 and 97.11 % sequence similarities, respectively).However, DNA-DNA hybridization analysis did not reveal any relatedness at the species level. Further differences were apparent in biochemical traits, and fatty acid, quinone and polyamine profiles leading us to conclude that strain SPC-1 T represents a novel species of the genus Sphingomonas, for which the name Sphingomonas cynarae sp. nov. is proposed; the type strain is SPC-1 T (5JCM 17498 T 5ITEM 13494 T ). A component analysis of the exopolysaccharide suggested that it represents a novel type of sphingan containing glucose, rhamnose, mannose and galactose, while glucuronic acid, which is commonly found in sphingans, was not detected.Sphingomonads are a group of alphaproteobacteria that are widely distributed in nature, commonly isolated from many land and water habitats, as well as from plant phyllosphere and rhizosphere, clinical specimens, and other sources. Besides their ecological role, these micro-organisms have a great potential for biotechnological applications in the degradation, bioremediation and wastewater treatment of xenobiotic pollutants, as bacterial antagonists of phytopathogenic fungi and for the production of industrially useful polymers and enzymes ( Abbreviations: EPS, exopolysaccharide; FAME, fatty acid methyl ester; HPAEC-PAD, high-performance anion-exchange chromatography with pulsed amperometric detection; TFA, trifluoroacetic acid.