Johnson Joshua C, Appels Rudi, Bhave Mrinal
School of Molecular Sciences, Victoria University, P.O. Box 14428, Melbourne, Victoria, MC 8001, Australia.
Funct Integr Genomics. 2006 Apr;6(2):104-21. doi: 10.1007/s10142-005-0003-2. Epub 2005 Sep 27.
The storage protein polymers in the endosperm, stabilised by disulphide bonds, determine a number of processing qualities of wheat dough. The enzyme protein disulphide isomerase (PDI), involved in the formation of disulphide bonds, is strongly suggested to play a role in the formation of wheat storage protein bodies. Reports of the rice mutant esp2 exhibiting aberrant storage protein deposition in conjunction with a lack of PDI expression provided strong indications of a direct role for PDI in storage protein deposition. The potential significance of wheat PDI prompted the present studies into exploring any orthology between wheat PDI genes and rice PDI and esp2 loci. By designing allele-specific (AS)-polymerase chain reaction (PCR) markers, two of the three wheat PDI genes could be genetically mapped to group 4 chromosomes and showed close association with GERMIN genes. Physical mapping led to localisation of wheat PDI genes to chromosomal "bins" on the proximal section of chromosome 4AL and distal sections of 4BS and 4DS. Identification of the putative PDI gene of rice and its comparison to the esp2 locus revealed that they were present at similar positions on the short arm of chromosome 11. Analysis of a large section of the PDI-containing section of rice chromosome 11S revealed a number of putative orthologues from The Institute for Genomic Research Triticum aestivum Gene Index database, of which five had been mapped, each localising to group 4 chromosomes, many in good agreement with our mapping results. The results strongly suggest a close linkage between the esp2 marker and the PDI gene of rice and an orthology between the PDI loci of rice and wheat and predict quantitative-trait loci involved in storage protein deposition at the PDI loci.
胚乳中的贮藏蛋白聚合物通过二硫键得以稳定，决定了小麦面团的多种加工品质。参与二硫键形成的酶蛋白二硫键异构酶（PDI），被强烈认为在小麦贮藏蛋白体的形成中发挥作用。水稻突变体esp2表现出异常的贮藏蛋白沉积且缺乏PDI表达的报道，有力地表明了PDI在贮藏蛋白沉积中具有直接作用。小麦PDI的潜在重要性促使了本研究去探索小麦PDI基因与水稻PDI及esp2位点之间的任何同源关系。通过设计等位基因特异性（AS）-聚合酶链反应（PCR）标记，三个小麦PDI基因中的两个能够被遗传定位到4组染色体上，并显示出与GERMIN基因紧密关联。物理定位将小麦PDI基因定位到4AL染色体近端区域以及4BS和4DS染色体远端区域的染色体“ bins”上。水稻推定的PDI基因的鉴定及其与esp2位点的比较表明，它们位于第11号染色体短臂的相似位置。对水稻第11号染色体短臂含PDI区域的一大段分析揭示了来自基因组研究所普通小麦基因索引数据库的许多推定同源物，其中五个已被定位，每个都定位到4组染色体上，许多与我们的定位结果高度一致。结果有力地表明了esp2标记与水稻的PDI基因之间存在紧密联系，以及水稻和小麦的PDI位点之间存在同源关系，并预测了参与PDI位点贮藏蛋白沉积的数量性状位点。
