Wong Joshua H, Kim Yong-Bum, Ren Pei-Hsien, Cai Nick, Cho Myeong-Je, Hedden Peter, Lemaux Peggy G, Buchanan Bob B
Department of Plant and Microbial Biology, University of California, 111 Koshland Hall, Berkeley, CA 94720, USA.
Proc Natl Acad Sci U S A. 2002 Dec 10;99(25):16325-30. doi: 10.1073/pnas.212641999. Epub 2002 Nov 27.
Homozygous lines of barley overexpressing a wheat thioredoxin h transgene (up to 30-fold) were generated earlier by using a B(1)-hordein promoter with a signal peptide sequence for targeting to the protein body and found to be enriched in starch debranching enzyme (pullulanase). Here, we describe the effect of biochemically active, overexpressed thioredoxin h on germination and the onset of alpha-amylase activity. Relative to null segregant controls lacking the transgene, homozygotes overexpressing thioredoxin h effected (i) an acceleration in the rate of germination and appearance of alpha-amylase activity with a 1.6- to 2.8-fold increase in gibberellin A(1) (GA(1)) content; (ii) a similar acceleration in the appearance of the alpha-amylase activity in deembryonated transgenic grain incubated with gibberellic acid; (iii) a 35% increase in the ratio of relative reduction (abundance of SH) of the propanol soluble proteins (hordein I fraction); and (iv) an increase in extractable and soluble protein of 5-12% and 11-35%, respectively. Thioredoxin h, which was highly reduced in the dry grain, was degraded in both the null segregant and homozygote after imbibition. The increase in alpha-amylase activity and protein reduction status was accompanied by a shift in the distribution of protein from the insoluble to the soluble fraction. The results provide evidence that thioredoxin h of the starchy endosperm communicates with adjoining tissues, thereby regulating their activities, notably by accelerating germination of the embryo and the appearance of alpha-amylase released by the aleurone.
早前通过使用带有靶向蛋白体信号肽序列的B(1)-大麦醇溶蛋白启动子，培育出了过表达小麦硫氧还蛋白h转基因（高达30倍）的大麦纯合系，发现其富含淀粉脱支酶（支链淀粉酶）。在此，我们描述了具有生化活性的过表达硫氧还蛋白h对发芽和α-淀粉酶活性起始的影响。相对于缺乏转基因的无效分离对照，过表达硫氧还蛋白h的纯合子导致：(i) 发芽率和α-淀粉酶活性出现加速，赤霉素A(1)（GA(1)）含量增加1.6至2.8倍；(ii) 用赤霉素处理的去胚转基因谷物中α-淀粉酶活性的出现有类似加速；(iii) 丙醇可溶性蛋白（大麦醇溶蛋白I组分）的相对还原率（SH丰度）增加35%；(iv) 可提取蛋白和可溶性蛋白分别增加5 - 12%和11 - 35%。在干种子中高度还原的硫氧还蛋白h在吸水后在无效分离对照和纯合子中均被降解。α-淀粉酶活性的增加和蛋白质还原状态伴随着蛋白质分布从不可溶部分向可溶部分的转变。结果提供了证据，表明淀粉胚乳中的硫氧还蛋白h与相邻组织进行通讯，从而调节它们的活性，特别是通过加速胚的发芽和糊粉层释放的α-淀粉酶的出现。
