Bhattacharyya M, Martin C, Smith A
Samuel Roberts Noble Foundation, Plant Biology Division, Ardmore, OK 73402.
Plant Mol Biol. 1993 Jun;22(3):525-31. doi: 10.1007/BF00015981.
The wrinkled-seed mutant (rr) of pea (Pisum sativum L.) arose through mutation of the gene encoding starch-branching enzyme isoform I (SBE1) by insertion of a transposon-like element into the coding sequence. Two isoforms of starch-branching enzyme have been documented in the developing pea embryo. The second isoform, SBEII, is expressed towards the later stages of embryo development while SBEI is expressed highly in the early stages. Due to mutation of SBEI the total amount of starch and the proportion of amylopectin, a branched starch polymer, are greatly reduced in the wrinkled (rr) line as compared to that in the wild-type, round (RR) line. Consequently, the level of sucrose in the rr line is nearly two fold that of the RR line. Increased sucrose concentration in the developing embryos of this mutant line causes increased uptake of water and thereby increases the cell size and fresh weight. During seed maturation in these mutant seeds a greater loss of water occurs. As a result, the wrinkled seed phenotype develops. Besides this morphological variation, the mutation also causes changes in the amount of lipid and of one storage protein, legumin. This review article discusses the role of the SBEI enzyme in causing such metabolic changes in the developing embryos with the implication that metabolism can play a central role in plant development.
豌豆（Pisum sativum L.）的皱粒种子突变体（rr）是由于编码淀粉分支酶同工型I（SBE1）的基因发生突变，一个类似转座子的元件插入到编码序列中而产生的。在发育中的豌豆胚中已发现两种淀粉分支酶同工型。第二种同工型SBEII在胚发育后期表达，而SBEI在早期高度表达。由于SBEI发生突变，与野生型圆粒（RR）品系相比，皱粒（rr）品系中淀粉的总量和支链淀粉（一种分支淀粉聚合物）的比例大大降低。因此，rr品系中蔗糖水平几乎是RR品系的两倍。该突变品系发育中的胚中蔗糖浓度升高导致水分吸收增加，从而增大细胞大小和鲜重。在这些突变种子的成熟过程中，水分损失更大。结果，形成了皱粒种子表型。除了这种形态变化外，该突变还导致脂质和一种贮藏蛋白（豆球蛋白）含量的变化。这篇综述文章讨论了SBEI酶在发育中的胚中引起这种代谢变化所起的作用，意味着代谢在植物发育中可能起核心作用。
