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Aurones belong to a small class of flavonoids that provide yellow color in some floricultural plants including snapdragon. To explore novel flower coloration, two full-length cDNAs encoding chalcone 4'-O-glucosyltransferase (designated as SRY4'CGT) and aureusidin synthase (designated as SRYAS1) in the aurone biosynthetic pathway were cloned from yellow flowers of snapdragon (Antirrhinum majus cv. Ribbon Yellow). Binary vectors were constructed and transformed separately into Petunia hybrida harboring blue flowers. Only a few flowers in 4 out of 9 transgenic SRY4'CGT plants showed variegated blue-white sectors; as time passed, amounts of variegated flowers and proportion of white sectors in the background blue color of the new-born flowers gradually increased, until finally, the petal color was completely white in all late-born flowers. In contrast, a few flowers in 3 out of 13 transgenic SRYAS1 plants showed variegated blue-white sectors; but, the amounts of variegated flowers did not increase over the whole flowering stage, and no complete white flowers were observed. RNA samples isolated from blue and white sectors of T1 transgenic SRY4'CGT plants were analyzed by reverse transcription-PCR, transgenic SRY4'CGT transcripts were detected in both sectors; however, transcripts of an upstream gene, chalcone synthase (CHS), were abundantly detected in the blue sectors but largely reduced in the white sectors, suggesting that the expression of CHS gene was suppressed in white sectors of transgenic plants. Furthermore, HPLC coupled with mass spectrometry demonstrated cyandin, malvidin and their derivatives were absent in white sectors, causing the white phenotype. Our findings may be attractive to molecular breeders.

A 93-kb region (D region) of plasmid pAE1 of Alcaligenes eutrophus H1 has been found to have a high rate of spontaneous deletion. In this study, we constructed a restriction endonuclease map and carried out limited sequencing of an approximately 100-kb region from pAE1 which includes the D region (the deleted region) in order to detect and characterize repetitive sequences. Two types of repetitive sequences, the R1 and R2 sequences, were observed to flank the D region; within the D region are three copies of insertion element ISAE1. The R1 and R2 sequences are arranged in direct and inverted orientations, respectively. Molecular analysis of the end product of the deletion is consistent with the hypothesis that the loss of the D-region DNA is the result of recombination between two copies of the R1 sequence. The R1 sequence encodes a 415-amino-acid protein which exhibits substantial sequence similarity to the lambda integrase family of site-specific recombinases. Its genetic function remains to be determined.Alcaligenes eutrophus is a gram-negative facultative chemolithoautotrophic (autotrophic) bacterium which can oxidize hydrogen gas for carbon dioxide fixation. Large plasmids (350 to 450 kb) carrying the structural genes for the two hydrogenases, the membrane-bound particulate hydrogenase (hoxP) and the NAD ϩ -reducing soluble hydrogenase (hoxS), have been determined to be present in several A. eutrophus strains (7, 13, 22). The plasmid from strain H16, pHG1, has been reported to carry genes necessary for carbon dioxide fixation (cfx genes). The cfx genes are adjacent to the hox gene clusters and have a duplicated copy situated on the chromosome (11). An estimated total of 100 kb of pHG1 DNA is required to encode genes involved in the autotrophic growth of A. eutrophus H16.Similar to pHG1, the large plasmid of A. eutrophus H1, pAE1, carries the genetic determinants of autotrophic growth (4,14,22). Several variants of pAE1 that were smaller in size were observed in HoxP Ϫ mutants generated by Tn5 mutagenesis, e.g., strain WW1-12. A similar deletion of at least 50 kb of pAE1 DNA has also been observed in strain H1-4, which is a mitomycin-generated HoxS Ϫ derivative of strain H1, as well as other Tn5-carrying strains without an obvious defect in autotrophic growth (4,22). This frequently found deleted region is designated the D region of pAE1 (4). The aim of this work was to determine the extent and physical organization of the D region.Construction of the restriction endonuclease map of the D region. Southern hybridization analysis has indicated that the D region contains three copies of insertion element ISAE1 (14). Therefore, the ISAE1-containing DNA fragments from pAE1 were used as probes to screen an A. eutrophus genomic library constructed by cloning partially Sau3A-digested DNA of strain H1 into the BamHI site of Charon 40 DNA (6). The restriction endonuclease map of an approximately 100-kb pAE1 DNA was established by aligning the overlapping clones obtained by DNA walking (Fig. 1A). Most of the probes sel...