SUMMARYThe structures, evolution and functions of alcohol dehydrogenase gene families and their products have been scrutinized for half a century. Our understanding of the enzyme structure and catalytic activity of plant alcohol dehydrogenase (ADH-P) is based on the vast amount of information available for its animal counterpart. The probable origins of the enzyme from a simple b-coil and eventual emergence from a glutathione-dependent formaldehyde dehydrogenase have been well described. There is compelling evidence that the small ADH gene families found in plants today are the survivors of multiple rounds of gene expansion and contraction. To the probable original function of their products in the terminal reaction of anaerobic fermentation have been added roles in yeast-like aerobic fermentation and the production of characteristic scents that act to attract animals that serve as pollinators or agents of seed dispersal and to protect against herbivores.

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EcoRPI restriction endonuclease fragments from a A proviral DNA hybrid containing the entire presumptive avian myeloblastosis virus (AMV) provirus, and from a A proviral hybrid containing a partial myeloblastosis-associated virus type 1 (MAV-1-like provirus were compared by heteroduplex analysis. The cloned presumptive AMV provirus was also analyzed by electron microscopy, using R-loop formation with purified 35S RNA isolated from virions of the standard AMV complex. The results indicate that the putative AMV genome contains a segment absent in its MAV-1-like helper virus. This segment represents a substitution in the region of the genome that in MAV-1 virus is occupied by the envelope gene and is approximately 9004: 160 nucleotide pairs in length. Hybridization of specific probes from the presumptive AMV genome to Southern blots of EcoRI-digested cellular DNA has revealed that these substituted sequences are homologous to chicken and duck DNA that is not related to chicken endogenous proviral sequences.

Plant Myb proteins represent a group of transcription factors which have a DNA-binding domain similar to that found in the products of the animal myb proto-oncogenes. Members of the Myb family regulate the biosynthesis of phenylpropanoids, including anthocyanin and phlobaphene pigments, in several species. In this study, PCR with degenerate primers was used to analyse the presence of myb-like genes in pea (Pisum sativum L.). A fragment representing a flower bud-expressed gene, designated myb26, was recovered, and a full length cDNA was isolated from a pea flower bud cDNA library. The predicted protein is 217 amino acids long and its Myb-domain and carboxy terminal region show extensive homology to the snap-dragon proteins Myb305 and Myb340, both of which regulate phenylpropanoid biosynthesis. Expression of myb26 is flower-specific and parallels the expression of flavonoid biosynthetic genes, increasing as the flower bud matures and intensifies in colour. However, myb26 represents neither of the two known regulatory genes for anthocyanin production in pea, nor does it complement mutants of the myb-like anthocyanin regulatory gene an2 in petunia. Myb26 was expressed in E. coli as a fusion protein. It was shown that in vitro Myb26 recognizes the c-Myb and P-box-like binding sites representing cis-elements in the promoter regions of several phenylpropanoid biosynthetic genes. The results suggest that myb26 is a previously undefined gene involved in regulation of some aspect of phenylpropanoid production in pea.

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