Beta-amylases (BAMs), key enzymes in starch hydrolysis, play an important role in plant growth, development, and resistance to abiotic stress. To mine the saline-alkali tolerance-related BAM genes in alfalfa (Medicago sativa L.), we identified MsBAM genes in the whole genome. The physicochemical properties, phylogeny, gene structures, conserved motifs, secondary structures, promoter cis-acting elements, chromosome localization, and gene replication relationships of BAM gene family members were analyzed. RNA-seq and quantitative real-time PCR (qRT-PCR) were employed to analyze the expression patterns of BAM family members under saline-alkali stress. The results showed that 54 BAM genes were identified in the genome, which were classified into 8 subgroups according to the phylogenetic tree. The members of the same subgroup had similar gene structures except that those of subgroups 1 and 7 had large differences. Conserved motif analysis showed that all MsBAM proteins had a typical glycohydrolysis domain. The chromosome localization analysis showed that MsBAM gene family members were unevenly distributed on 27 chromosomes. The duplication of gene segments led to the increase in BAM gene number in alfalfa. The promoters of BAM genes contained a large number of elements in response to plant hormones and stress. Transcriptome data and qRT-PCR results showed that the expression levels of most MsBAM genes were up-regulated in response to saline-alkali stress. Under the saline-alkali stress, the expression levels of 28 genes, including MsBAM6, were up-regulated on days 1 and 7, and those of 5 genes, including MsBAM9, were up-regulated by over 2 folds. In addition, under salt-alkali stress, BAM activity and soluble sugar content were significantly increased. These results indicate that BAM genes play a key role in alfalfa in response to saline-alkali stress, laying a foundation for further research in this field.
Medicago sativa/physiology* ; beta-Amylase/metabolism* ; Phylogeny ; Gene Expression Regulation, Plant ; Stress, Physiological/genetics* ; Multigene Family ; Alkalies ; Plant Proteins/genetics*

Genetic modification of barley variety can be an efficient way to improve beer quality. The objective of this study was to understand the effect of trxS gene on hydrolases activities in transgenic and non-transgenic barley seeds. The results showed that alpha-amylase, free beta-amylase and limit dextrinase activity were increased in transgenic seeds in comparison with non-transgenic seeds. Sulfhydryl content of protein in transgenic seeds was also higher than that in non-transgenic seeds, suggesting that trxS gene could express in barley seeds, which opens a new way for breeding new barley varieties to improve beer quality.
Germination ; genetics ; Glucosyltransferases ; metabolism ; Hordeum ; enzymology ; genetics ; Plants, Genetically Modified ; enzymology ; genetics ; Seeds ; enzymology ; genetics ; Sulfhydryl Compounds ; metabolism ; Thioredoxins ; genetics ; alpha-Amylases ; metabolism ; beta-Amylase ; metabolism

A beta-amylase gene (amyG) was cloned from a Bacillus megaterium WS06 and expressed in the Escherichia coli. Nucleotide sequence anlysis showed the amyG gene is composed of 1638 bp (545 amino acid residues with a Mr of 60.194 kD). The AmyG shows 94.5% sequence homologies with beta-amylase from Bacillus megaterium DSM319 and presents a normal beta-amylase primary structure, constituted by three parts: the N-terminal signal sequence, the catalytic domain and the C-terminal starch binding domains. The deduced amino acid sequence revealed that several highly conserved regions of the glycosylhydrolase family 14. The amyG gene was overexpressed using the pET21a vector and Escherichia coli BL21(DE3). The recombinant enzyme was purified 7.4 fold to electrophoretic homogeneity and had a Mr of 57 kD (by SDS-PAGE). The enzyme was optimally active at pH 7.0 and 60 degrees C and showed stability at the temperature below 60 degrees C. This enzyme efficiently hydrolyzed starch to yield maltose from non-reducing chain ends by exo-cleavage mode.
Bacillus megaterium ; enzymology ; genetics ; Cloning, Molecular ; Escherichia coli ; genetics ; metabolism ; Genetic Vectors ; genetics ; Recombinant Proteins ; biosynthesis ; genetics ; metabolism ; Sequence Analysis, Protein ; Sequence Homology, Amino Acid ; Temperature ; beta-Amylase ; biosynthesis ; genetics ; metabolism

The effects of different timing of N fertilizer application at the same rate on grain beta-amylase activity, protein concentration, weight and malt quality of barley were studied. Grain beta-amylase activity and protein concentration were significantly higher in treatments where all top-dressed N fertilizer was applied at booting stage only or equally applied at two-leaf stage and booting stage than in the treatment where all top-dressed N fertilizer was applied at two-leaf age stage only. On the other hand, grain weight and malt extract decreased with increased N application at booting stage. There were obvious differences between barley varieties and experimental years in the grain and malt quality response to the timing of N fertilizer application. It was found that grain protein concentration was significantly and positively correlated with beta-amylase activity, but significantly and negatively correlated with malt extract and Kolbach index. The effect of grain protein concentration on malt quality was predominant over the effect of grain beta-amylase activity.
Agriculture ; methods ; Edible Grain ; chemistry ; drug effects ; metabolism ; Enzyme Activation ; Fertilizers ; Hordeum ; drug effects ; metabolism ; Nitrogen ; administration & dosage ; Plant Proteins ; metabolism ; Statistics as Topic ; Time Factors ; beta-Amylase ; chemistry ; metabolism