Kreis M, Shewry P R, Forde B G, Rahman S, Bahramian M B, Miflin B J
Biochem Genet. 1984 Apr;22(3-4):231-55. doi: 10.1007/BF00484227.
The lys 3a gene present in the barley mutant Ris phi 1508 results in an increased content of lysine in the grain. Previous studies have shown that this increase results from a decreased accumulation of hordein and an increase in other more lysine-rich proteins and in free amino acids. We report here a detailed examination of the effects of this gene on the different groups of hordein polypeptides and the mRNAs encoding them. The amounts of the two major groups of hordein polypeptides (B and C hordein ) were reduced to about 20 and 7%, respectively, of those present in the parental variety ( Bomi ), with a greater effect on one of the two subfamilies of B polypeptides. In contrast, the amounts of D hordein polypeptides were increased fourfold. In vitro translations of polysomal and total cellular RNA fractions showed similar effects on the relative amounts of hordein products synthesized. More detailed analyses of the populations of hordein mRNAs were made using specific cDNA clones and hybrid-selection translation, Northern hybridization, and "hybrid-dot" analysis. Only traces of mRNAs for "C" hordein were detected, while the abundances of mRNAs for the two subfamilies of B hordeins were reduced to 40 and 5% of those in Bomi . The amount of mRNA for D hordein was increased twofold. A cDNA clone related to B hordein was used to analyze genomic DNA fractions by Southern hybridization. The lys 3a gene had no effect on either the number (about 10) or the organization of the B hordein genes. These studies clearly demonstrate that the effects of the lys 3a gene on the amounts of the hordein polypeptides are closely related to changes in the amounts of the mRNAs encoding them. Although the exact effect of the gene remains unknown, it is most likely to be either at transcription or on the early processing of the mRNA.
大麦突变体Ris phi 1508中存在的lys 3a基因导致籽粒中赖氨酸含量增加。先前的研究表明，这种增加是由于大麦醇溶蛋白积累减少以及其他富含赖氨酸的蛋白质和游离氨基酸增加所致。我们在此报告对该基因对不同组大麦醇溶蛋白多肽及其编码mRNA的影响的详细研究。两组主要的大麦醇溶蛋白多肽（B和C大麦醇溶蛋白）的含量分别降至亲本品种（Bomi）中含量的约20%和7%，对B多肽的两个亚家族之一影响更大。相比之下，D大麦醇溶蛋白多肽的含量增加了四倍。多核糖体和总细胞RNA组分的体外翻译对合成的大麦醇溶蛋白产物的相对量显示出类似的影响。使用特异性cDNA克隆以及杂交选择翻译、Northern杂交和“杂交点”分析对大麦醇溶蛋白mRNA群体进行了更详细的分析。仅检测到痕量的“C”大麦醇溶蛋白mRNA，而B大麦醇溶蛋白两个亚家族的mRNA丰度分别降至Bomi中的40%和5%。D大麦醇溶蛋白的mRNA量增加了两倍。一个与B大麦醇溶蛋白相关的cDNA克隆用于通过Southern杂交分析基因组DNA组分。lys 3a基因对B大麦醇溶蛋白基因的数量（约10个）或组织均无影响。这些研究清楚地表明，lys 3a基因对大麦醇溶蛋白多肽量的影响与编码它们的mRNA量的变化密切相关。尽管该基因的确切作用尚不清楚，但最有可能是在转录水平或mRNA的早期加工过程中。
