John Innes Institute and AFRC Institute of Plant Science Research, Colney Lane, NR4 7UH, Norwich, UK.
Planta. 1990 Jun;181(3):310-5. doi: 10.1007/BF00195881.
The effect of a reduction of the activity of starch-branching enzyme (1,4-α-(D)-glucan, 1,4-α-(D)-glucan-6-glycosyl transferase; EC 2.4.1.18) on photosynthetic starch synthesis and photosynthate partitioning has been studied in leaves of pea (Pisum sativum L.). Leaves of wrinkled-seeded peas, recessive at the rugosus locus (rr), contained lower activity of branching enzyme than leaves of near-isogenic round-seeded peas, dominant at the rugosus locus (RR). Western blots showed that one isoform of the enzyme is absent from rr leaves, corresponding to the isoform that is absent from rr embryos. RR and rr leaves had identical rates of starch synthesis and photosynthesis at low irradiances. At high irradiances the rate of starch synthesis was decreased by up to 40% in rr relative to RR leaves. There was no corresponding increase of sucrose synthesis in rr leaves; instead, the rate of photosynthesis was decreased. This inhibition of photosynthesis was more marked at low than at high temperatures and was accompanied by increased oscillatory behaviour, rr leaves contained higher levels of ADP glucose and glycerate 3-phosphate than RR leaves in low and high light. The contribution of these results to our understanding of the distribution of control in the pathways of starch and sucrose synthesis is discussed.
研究了降低淀粉分支酶（1,4-α-（D）-葡聚糖，1,4-α-（D）-葡聚糖-6-糖基转移酶；EC 2.4.1.18）的活性对豌豆（Pisum sativum L.）叶片光合作用淀粉合成和光合产物分配的影响。皱粒豌豆（rr）隐性基因的叶片中分支酶活性低于近等基因圆形粒豌豆（RR）的叶片。Western blot 显示，rr 叶片中缺少一种同工酶，这种同工酶也存在于 rr 胚中。RR 和 rr 叶片在低辐照度下具有相同的淀粉合成和光合作用速率。在高光强下，rr 叶片的淀粉合成速率比 RR 叶片降低了多达 40%。rr 叶片中没有相应的蔗糖合成增加；相反，光合作用速率降低。这种光合作用的抑制在低温下比高温下更为明显，并且伴随着振荡行为的增加。rr 叶片在低光和高光下比 RR 叶片含有更高水平的 ADP 葡萄糖和甘油 3-磷酸。讨论了这些结果对我们理解淀粉和蔗糖合成途径中控制分布的贡献。
