Australian Herbicide Resistance Initiative, School of Plant Biology, The University of Western Australia, Crawley, Australia.
Ann Bot. 2012 Dec;110(8):1641-50. doi: 10.1093/aob/mcs213. Epub 2012 Sep 21.
α-Amylase in grass caryopses (seeds) is usually expressed upon commencement of germination and is rarely seen in dry, mature seeds. A heat-stable α-amylase activity was unexpectedly selected for expression in dry annual ryegrass (Lolium rigidum) seeds during targeted selection for low primary dormancy. The aim of this study was to characterize this constitutive activity biochemically and determine if its presence conferred insensitivity to the germination inhibitors abscisic acid and benzoxazolinone.
α-Amylase activity in developing, mature and germinating seeds from the selected (low-dormancy) and a field-collected (dormant) population was characterized by native activity PAGE. The response of seed germination and α-amylase activity to abscisic acid and benzoxazolinone was assessed. Using an alginate affinity matrix, α-amylase was purified from dry and germinating seeds for analysis of its enzymatic properties.
The constitutive α-amylase activity appeared late during seed development and was mainly localized in the aleurone; in germinating seeds, this activity was responsive to both glucose and gibberellin. It migrated differently on native PAGE compared with the major activities in germinating seeds of the dormant population, but the enzymatic properties of α-amylase purified from the low-dormancy and dormant seeds were largely indistinguishable. Seed imbibition on benzoxazolinone had little effect on the low-dormancy seeds but greatly inhibited germination and α-amylase activity in the dormant population.
The constitutive α-amylase activity in annual ryegrass seeds selected for low dormancy is electrophoretically different from that in germinating seeds and its presence confers insensitivity to benzoxazolinone. The concurrent selection of low dormancy and constitutive α-amylase activity may help to enhance seedling establishment under competitive conditions.
禾本科植物颖果（种子）中的α-淀粉酶通常在萌发开始时表达，在干燥、成熟的种子中很少见。在针对低初始休眠的目标选择中，出乎意料地选择了一种热稳定的α-淀粉酶活性在干燥的一年生黑麦草（Lolium rigidum）种子中表达。本研究的目的是从生化角度表征这种组成型活性，并确定其存在是否赋予对萌发抑制剂脱落酸和苯并恶唑啉酮的不敏感性。
通过天然活性 PAGE 对来自选定（低休眠）和田间收集（休眠）群体的发育、成熟和萌发种子中的α-淀粉酶活性进行了表征。评估了种子萌发和α-淀粉酶活性对脱落酸和苯并恶唑啉酮的反应。使用藻酸盐亲和基质，从干燥和萌发的种子中纯化α-淀粉酶，用于分析其酶学特性。
组成型α-淀粉酶活性在种子发育后期出现，主要定位于糊粉层；在萌发的种子中，这种活性对葡萄糖和赤霉素都有反应。与休眠种群萌发种子中的主要活性相比，它在天然 PAGE 上的迁移方式不同，但从低休眠和休眠种子中纯化的α-淀粉酶的酶学特性在很大程度上是不可区分的。种子在苯并恶唑啉酮上的吸胀对低休眠种子几乎没有影响，但对休眠种群的萌发和α-淀粉酶活性有很大抑制作用。
低休眠选择的一年生黑麦草种子中的组成型α-淀粉酶活性在电泳上与萌发种子中的不同，其存在赋予对苯并恶唑啉酮的不敏感性。低休眠和组成型α-淀粉酶活性的同时选择可能有助于在竞争条件下增强幼苗的建立。
