A novel wheat alpha-amylase gene (alpha-Amy3)

Summary A genomic clone of a wheat -amylase gene (Amy3/33) was identified, on the basis of hybridisation properties, as different from -Amy1 and -Amy2 genes which had been characterised previously. The nucleotide sequence revealed that this gene has the normal sequence motifs of an active gene and an open reading frame interrupted by two introns. The protein sequence encoded by this open reading frame is recognisably similar to that of -amylase from the -Amy1 and -Amy2 genes and there is high sequence homology in all three proteins at the putative active sites and Ca⁺⁺ binding region. In addition, the introns are at positions equivalent to the position of introns in the -Amy1 and -Amy2 genes. However, the sequence was less similar to -Amy1 and -Amy2 than these are to each other. Southern blot analysis showed that the Amy3/33 DNA is one of a small multigene family carried on a different chromosome (group 5) from either the -Amy1 or -Amy2 genes. A further difference from the -Amy1 and -Amy2 genes was the pattern of expression. Amy3/33 was expressed only in immature grains and, unlike the -Amy1 and -Amy2 genes, not at all in germinating aleurones. These data suggested therefore that this gene represents a third type of -amylase gene, not described before, which shares a common evolutionary ancestor with the -Amy1 and -Amy2 genes.     

An unusual wheat insertion sequence (WIS1) lies upstream of an alpha-amylase gene in hexaploid wheat, and carries a "minisatellite" array

Summary Comparison of the 5′ flanking regions of three α-amylase genes from chromosome 6B of hexaploid wheat by heteroduplex and sequence analysis revealed the presence of a 1.6 kb stem-loop insertion sequence (WIS1) in one of them. Polymorphism among hexaploid wheat varieties suggests the relatively recent insertion/excision of this sequence from its present position. The complete sequence of the stem-loop insertion shows that it has many of the features found in transposable elements, including target site duplication and terminal inverted repeats. One unusual feature is a tandem array of direct repeats comprising a wheat “minisatellite” sequence. Both the insertion sequence and the minisatellite are found at multiple locations in the wheat genome, but the functional significance of their association in WIS1 is unknown. The minisatellite arrays share a common core structure, and long arrays are polymorphic between different hexaploid varieties.     

The structure and evolution of the spider monkey delta-globin gene

We have isolated the delta-globin gene of the New-World spider monkey, Ateles geoffroyi, and compared its nucleotide sequence with those of other primate delta- and beta-globin genes. Among primate delta-globin genes, the rate of nonsynonymous substitutions is much less than the rate of synonymous substitutions. This suggests that primate delta- globin genes may remain under evolutionary conservation, perhaps because hemoglobin A2 has an as yet unknown physiological importance.      

Somatic excision of the Mu1 transposable element of maize.

The Mu transposons of the Robertsons's Mutator transposable element system in maize are unusual in many respects, when compared to the other known plant transposon systems. The excision of these elements occurs late in somatic tissues and very rarely in the germ line. Unlike the other plant transposons, there is no experimental evidence directly linking Mu element excision and integration. We have analyzed the excision products generated by a Mu1 transposon inserted into the bronze 1 locus of maize. We find that the excision products or 'footprints' left by the Mu1 element resemble those of the other plant transposable elements, rather than those of the animal transposable element systems. We also find some novel types of footprints resembling recombinational events. We suggest that the Mu1 element can promote intrachromosomal crossovers and conversions near its site of insertion, and that this may be another mechanism by which transposons can accelerate the evolution of genomes.     

α-amylase genes of wheat are two multigene families which are differentially expressed

Plant Molecular Biology - The α-Amy1 and α-Amy2 genes of wheat produce distinct subsets of α-amylase isozymes which show different patterns of expression in wheat aleurone cells and...     

Biochemical pathways in prokaryotes can be traced backward through evolutionary time

For the first time, a credible prokaryotic phylogenetic tree is being assembled by Woese and others using quantitative sequence analysis of oligonucleotides in the highly conservative rRNA. This provides an evolutionary scale against which the evolutionary steps that led to the arrangement and regulation of contemporary biochemical pathways can be measured. This paper presents an emerging evolutionary picture of aromatic amino acid biosynthesis within a large superfamily assemblage of prokaryotes that is sufficiently developed to illustrate a new perspective that will be applicable to many other biochemical pathways.      

The evolutionary history of the amylase multigene family in Drosophila pseudoobscura

In Drosophila pseudoobscura, the amylase (Amy) multigene family is contained within a series of inversions, or gene arrangements, on the third chromosome. The Standard (ST), Santa Cruz (SC), and Tree Line (TL) inversions are central to the phylogeny of arrangements, and have clusters of other arrangements derived from them. The gene arrangements belonging to each of these three clusters have a characteristic number of Amy genes, ranging from three in ST to two in SC to one in TL. This distribution pattern can reflect a history of either duplications or deletions, although the data available in the past did not permit a decision between these alternatives. We provide unambiguous evidence that three Amy genes were present before the divergence of the ST, SC, and TL arrangements. Thus, the current status of the Amy multigene family is the result of deletions in the TL and SC arrangements, which created three new pseudogenes: TL Amy2-psi, TL Amy3-psi, and SC Amy3- psi. Analysis of pseudogene sequences revealed that, in the SC and ST arrangements, pseudogene evolution has been retarded, most likely due to the homogenization effect of gene conversion. Finally, by determining the original copy number, we have reconstructed the evolutionary history of the Amy multigene family and linked it with the evolution of the central gene arrangements.      

Coordinate Suppression of Mutations Caused by Robertson''s Mutator Transposons in Maize

Transposable elements from the Robertson's Mutator family are highly active insertional mutagens in maize. However, mutations caused by the insertion of responder (non-autonomous) elements frequently depend on the presence of active regulator (autonomous) elements for their phenotypic effects. The hcf106::Mu1 mutation has been previously shown to depend on Mu activity in this way. The dominant Lesion-mimic 28 mutation also requires Mu activity for its phenotypic effects. We have used double mutants to show that the loss of Mu activity results in the coordinate suppression of both mutant phenotypes. This loss can occur somatically resulting in large clones of cells that have a wild-type phenotype. Autonomous and non-autonomous Mutator elements within these clones are insensitive to digestion with methylation-sensitive enzymes, suggesting extensive methylation of CG and non-CG cytosine residues. Our data are consistent with the sectors being caused by the cycling of MuDR regulatory elements between active and inactive phases. The pattern of sectors suggests that they are clonal and that they are derived from the apical cells of the vegetative shoot meristem. We propose that these cells are more likely to undergo epigenetic loss of Mu activity because of their longer cell division cycle during shoot growth. Coordinate suppression of unlinked mutations can be used to perform mosaic analysis in maize.     

USE OF SENSORY EVALUATION FOR MEASURING DEODORIZING EFFECTS OF AN AIR CONDITIONER

The application of sensory methodology for measuring deodorizing effect of an air conditioner equipped with electric plasma was introduced. Deodorizing effect was measured using chemical and sensory methods at different time (0, 30 and 60 min) and mode (control, blowing and cooling) of an air conditioner. Smoke from a roll of cigarette in a closed room was used as a source of odor and the concentrations of acetic acid and ammonia were measured as odorous chemical components. As one of the sensory methods triangle test was used and as a first step to obtain deodorizing effects by triangle test, the threshold of each panelist was obtained as the log dilution ratio of odor concentration at which the difference from odorless air was detected. The odor concentration at each time and mode was calculated using the threshold of the panel and the deodorizing effect was obtained on the basis of the odor concentration. In addition to a triangle test, scaling methods such as category scaling or magnitude estimation were used to measure deodorizing effect of an air conditioner. Deodorizing effects by scaling methods were calculated based on odor intensity with time at each mode. The regression analysis was done between the efficacy of deodorizing effect by sensory test and those by acetic acid and ammonia, the R² values of the regression equations for triangle test, category scale, and magnitude estimation were 0.84, 0.72 and 0.69, respectively. Deodorizing effect by triangle test explained the decrease of acetic acid and ammonia better than those by category scaling or magnitude estimation while high cost and time consuming labor involved in triangle tests reduced the merit. The results of this study demonstrated that various sensory methods could be used to measure deodorizing effect of air conditioners and further researches on fast and reliable methods are needed to establish the official procedures.     

Analysis of splice donor and acceptor site function in a transposable gene trap derived from the maize element Activator

Gene trap vectors have been used in insertional mutagenesis in animal systems to clone genes with interesting patterns of expression. These vectors are designed to allow the expression of a reporter gene when the vector inserts into a transcribed region. In this paper we examine alternative splicing events that result in the expression of a GUS reporter gene carried on a Ds element which has been designed as a gene trap vector for plants. We have developed a rapid and reliable method based on PCR to study such events. Many splice donor sites were observed in the 3 Ac border. The relative frequency of utilisation of certain splice donor and acceptor sites differed between tobacco and Arabidopsis. A higher stringency of splicing was observed in Arabidopsis.