McCallum John, Thomas Ludivine, Shaw Martin, Pither-Joyce Meeghan, Leung Susanna, Cumming Mathew, McManus Michael T
The New Zealand Institute for Plant and Food Research Ltd., Private Bag 4704, Christchurch, New Zealand.
Institute of Molecular BioSciences, Massey University, Private Bag 11222, Palmerston North, New Zealand.
Phytochemistry. 2011 Jun;72(9):882-7. doi: 10.1016/j.phytochem.2011.03.006. Epub 2011 Apr 4.
Organosulfur compounds are major sinks for assimilated sulfate in onion (Allium cepa L.) and accumulation varies widely due to plant genotype and sulfur nutrition. In order to better characterise sulfur metabolism phenotypes and identify potential control points we compared plant composition and transcript accumulation of the primary sulfur assimilation pathway in the high pungency genotype 'W202A' and the low pungency genotype 'Texas Grano 438' grown hydroponically under S deficient (S-) and S-sufficient (S+) conditions. Accumulation of total S and alk(en)yl cysteine sulfoxide flavour precursors was significantly higher under S+ conditions and in 'W202A' in agreement with previous studies. Leaf sulfate and cysteine levels were significantly higher in 'W202A' and under S+. Glutathione levels were reduced by S- treatment but were not affected by genotype, suggesting that thiol pool sizes are regulated differently in mild and pungent onions. The only significant treatment effect observed on transcript accumulation in leaves was an elevated accumulation of O-acetyl serine thiol-lyase under S-. By contrast, transcript accumulation of all genes in roots was influenced by one or more treatments. APS reductase transcript level was not affected by genotype but was strongly increased by S-. Significant genotype×S treatment effects were observed in a root high affinity-sulfur transporter and ferredoxin-sulfite reductase. ATP sulfurylase transcript levels were significantly higher under S+ and in 'W202A'.
有机硫化合物是洋葱（Allium cepa L.）中同化硫酸盐的主要储存库，其积累量因植物基因型和硫营养状况而有很大差异。为了更好地表征硫代谢表型并确定潜在的控制点，我们比较了在缺硫（S-）和供硫充足（S+）条件下，水培生长的高辛辣基因型‘W202A’和低辛辣基因型‘Texas Grano 438’的植物组成以及初级硫同化途径的转录本积累情况。与先前的研究一致，在S+条件下以及‘W202A’中，总硫和烯（基）丙基半胱氨酸亚砜风味前体的积累量显著更高。‘W202A’和在S+条件下，叶片中的硫酸盐和半胱氨酸水平显著更高。谷胱甘肽水平因S-处理而降低，但不受基因型影响，这表明温和型和辛辣型洋葱中硫醇池大小的调节方式不同。在叶片转录本积累方面观察到的唯一显著处理效应是在S-条件下O-乙酰丝氨酸硫醇裂解酶的积累量升高。相比之下，根部所有基因的转录本积累都受到一种或多种处理的影响。APS还原酶转录水平不受基因型影响，但因S-处理而大幅增加。在根部高亲和力硫转运蛋白和铁氧还蛋白-亚硫酸盐还原酶中观察到显著的基因型×S处理效应。ATP硫酸化酶转录水平在S+条件下以及‘W202A’中显著更高。
