The ram1 mutant of Arabidopsis exhibits severely decreased β-amylase activity
The ram1 mutant of Arabidopsis exhibits severely decreased β-amylase activity
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DOI：
10.1104/pp.010723
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发表时间：
2001-12-01
期刊：
影响因子：
7.4
通讯作者：
Gibson, SI
中科院分区：
文献类型：
--
作者：
Laby, RJ;Kim, D;Gibson, SI
尽管进行了广泛的生化分析，植物β-淀粉酶的生物学功能仍不清楚。 β-淀粉酶在体外降解淀粉的事实表明它们可能在体内淀粉代谢中发挥作用。 β-淀粉酶也被建议用于防止高度聚合的多糖的积累，否则可能会阻碍通过韧皮部筛孔的通量。拟南芥突变体的鉴定和表征据报道，哥伦比亚的 β-淀粉酶活性水平大大降低。减少的 β-淀粉酶 1 (ram 1) 突变与编码拟南芥中主要形式 β-淀粉酶的基因有关。尽管拟南芥基因组包含九个已知或推定的 β-淀粉酶基因，但 ram1 突变导致莲座叶和花序（茎）中 β-淀粉酶活性几乎完全丧失的事实表明，受 ram1 突变影响的基因负责这些组织中存在的大部分 β-淀粉酶活性。 ram1 植物的叶子积累了野生型水平的淀粉、可溶性糖、花青素和叶绿素。携带ram1突变的植物还表现出野生型的韧皮部渗出率和总体生长率。这些结果表明，维持正常的淀粉水平、韧皮部渗出率和总体植物生长需要很少甚至不需要β-淀粉酶活性。
Despite extensive biochemical analyses, the biological function(s) of plant beta -amylases remains unclear. The fact that beta -amylases degrade starch in vitro suggests that they may play a role in starch metabolism in vivo. beta -Amylases have also been-suggested to prevent the accumulation of highly polymerized polysaccharides that might otherwise impede flux through phloem sieve pores. The identification and characterization of a mutant of Arabidopsis var. Columbia with greatly reduced levels of beta -amylase activity is reported here. The reduced beta -amylase 1 (ram 1) mutation ties in the gene encoding the major form of beta -amylase in Arabidopsis. Although the Arabidopsis genome contains nine known or putative beta -amylase genes, the fact that the ram1 mutation results in almost complete loss of beta -amylase activity in rosette leaves and inflorescences (stems) indicates that the gene affected by the ram1 mutation is responsible for most of the beta -amylase activity present in these tissues. The leaves of ram1 plants accumulate wild-type levels of starch, soluble sugars, anthocyanin, and chlorophyll. Plants carrying the ram1 mutation also exhibit wild-type rates of phloem exudation and of overall growth, These results suggest that little to no beta -amylase activity is required to maintain normal starch levels, rates of phloem exudation, and overall plant growth.