外源磷处理对水稻籽粒植酸含量及相关代谢基因表达的影响

利用水稻穗离体培养方法,对不同外源磷浓度下水稻籽粒植酸等磷化物含量的差异及其植酸代谢相关功能基因在灌浆过程中的表达特征进行了探讨。结果表明,水稻籽粒中的植酸、无机磷和总磷含量随外源磷处理浓度上升呈增加趋势,但磷处理对千粒重和单位籽粒中植酸积累量的影响因磷浓度水平而异,高磷处理会导致水稻千粒重和籽粒植酸积累绝对量的显著降低;外源磷处理浓度的上升,不仅会引起水稻籽粒中锌和铁元素含量的显著降低,而且会导致锌、铁营养的生物有效性下降;外源磷处理对水稻籽粒植酸含量的影响与不同磷处理下RINO1基因的相对表达量之间存在较密切关系,中磷浓度(3P)处理会诱导RINO1基因的表达,但高磷浓度(12P)会抑制RINO1基因的表达,RINO1是外源磷浓度处理对水稻籽粒植酸合成代谢过程产生调控作用的一个重要功能基因位点,而IPK2基因与水稻在不同磷浓度处理下的植酸含量变化无直接联系。

The Response of Phytic Acid and Its Expression Profiles in Rice (Oryza sativa L.) Grain as Induced by Phosphorus Supply

Phytic acid (PA) is the main storage form of phosphorus (P) in cereal grains. However, the relationship between external P supply and grain PA accumulation has not yet been fully understood. Two japonica rice cultivars were used to investigate the effects of phosphorus (P) treatments on grain phytic acid (PA) and its relation to inositol phosphate related genes expression profiles using a culture of detached panicle of rice (Oryza sativa L.). Results showed that high P level caused a significant increase in grain PA, inorganic P (Pi) and total P contents. However, grain weight and PA content per grain were P concentration dependent, and decreased under high P treatment (12P). High P supply decreased grain Zn and Fe concentrations, and their bio availabilities. Moreover, P treatment also influenced all four PA related genes expression (RINO1, ITP5/6K 6, IPK2 and IPK1), especially for RINO1, a rate limiting gene in PA synthesis and highly expressed in rice grains. Specifically, RION1 gene expression was up regulated at optimum P (3P) concentration, but was significantly down regulated under high P treatment (12P), which corresponded with the variation of grain PA content in rice, suggesting RION1 was a key metabolic gene in PA synthesis with P supply. In contrast, only a slight contribution of IPK2 gene was exhibited in PA synthesis induced by P supply.