Doria Enrico, Galleschi Luciano, Calucci Lucia, Pinzino Calogero, Pilu Roberto, Cassani Elena, Nielsen Erik
Dipartimento di Genetica e Microbiologia, Università degli Studi di Pavia, Via Ferrata 1, I-27100 Pavia, Italy.
J Exp Bot. 2009;60(3):967-78. doi: 10.1093/jxb/ern345. Epub 2009 Feb 9.
A maize mutant defective in the synthesis of phytic acid during seed maturation was used as a tool to study the consequences of the lack of this important reserve substance on seed survival. Data on germinability, free iron level, free radical relative abundance, protein carbonylation level, damage to DNA, degree of lipid peroxidation, alpha- and gamma-tocopherol amount and antioxidant capacity were recorded on seeds of maize B73 and of an isogenic low phytic acid mutant (lpa1-241), either unaged or incubated for 7 d in accelerated ageing conditions (46 degrees C and 100% relative humidity). The lpa1-241 mutant, compared to wild type (wt), showed a lower germination capacity, which decreased further after accelerated ageing. Whole lpa1-241 mutant kernels contained about 50% more free or weakly bound iron than wt ones and showed a higher content of free radicals, mainly concentrated in embryos; in addition, upon accelerated ageing, lpa1-241 seed proteins were more carbonylated and DNA was more damaged, whereas lipids did not appear to be more peroxidated, but the gamma-tocopherol content was decreased by about 50%. These findings can be interpreted in terms of previously reported but never proven antioxidant activity of phytic acid through iron complexation. Therefore, a novel role in plant seed physiology can be assigned to phytic acid, that is, protection against oxidative stress during the seed's life span. As in maize kernels the greater part of phytic acid (and thus of metal ions) is concentrated in the embryo, its antioxidant action may be of particular relevance in this crop.
一个在种子成熟过程中植酸合成有缺陷的玉米突变体被用作工具，来研究缺乏这种重要储备物质对种子存活的影响。记录了玉米B73及其同基因低植酸突变体（lpa1 - 241）种子的发芽能力、游离铁水平、自由基相对丰度、蛋白质羰基化水平、DNA损伤、脂质过氧化程度、α-生育酚和γ-生育酚含量以及抗氧化能力的数据，这些种子要么未老化，要么在加速老化条件（46摄氏度和100%相对湿度）下孵育7天。与野生型（wt）相比，lpa1 - 241突变体的发芽能力较低，在加速老化后进一步降低。整个lpa1 - 241突变体籽粒所含的游离或弱结合铁比wt籽粒多约50%，并且显示出更高的自由基含量，主要集中在胚中；此外，在加速老化后，lpa1 - 241种子蛋白质的羰基化程度更高，DNA损伤更严重，而脂质似乎没有更多的过氧化，但γ-生育酚含量降低了约50%。这些发现可以根据先前报道但从未得到证实的植酸通过铁络合的抗氧化活性来解释。因此，可以赋予植酸在植物种子生理学中的一个新作用，即在种子寿命期间抵御氧化应激。由于在玉米籽粒中，大部分植酸（以及金属离子）集中在胚中，其抗氧化作用在这种作物中可能特别重要。
