Abstract:

It is important to elucidate the mechanism of low phosphorus tolerance in rice for the improvement of utilization efficiency of soil phosphorus. With two different rice varieties, low-P tolerant variety Yi 2434 and low-P sensitive variety Tongjing 981, the gene expression related to phosphorus absorption and utilization in rice seedling roots were determined by using gene chip and qRT-PCR technology. The phosphorus content showed that compared with the control group, the phosphorus content in the leaves of Yi 2434 decreased by a less percentage than that in Tongjing 981 under low-P stress, indicating that Yi 2434 had a high efficiency in phosphorus absorption from low phosphorus medium compared with Tongjing 981. The gene chip results showed that the expressions of PHR1, osa-miR399s and SPXs triggered the phosphorus starvation signal pathway, and the induced gene expressions of APA, PAPs, MPE, PA, PEPC and VDAC1, C4-DT/MAT enhanced the synthesis and secretion of organophosphorus hydrolase and organic acid, promoted the reactivation of insoluble phosphorus in media, and the induced gene expressions of OsPT2 and OsPT6 accelerated the absorption of phosphorus in Yi 2434 roots under low-P stress. qRT-PCR results showed that the transcriptional levels of the eight key genes(PHR1,SPX,PAP,APA,PEPC,MFS,OsPT2,OsPT6 ) related to phosphorus starvation signal transduction, phosphorus activation and efficient absorption were continuously increased along with the low-P treatment in Yi 2434 roots. Furthermore, the transcriptional levels of these eight genes in Yi 2434 roots were significantly higher than those in Tongjing 981 roots under the low-P stress and the induced expression of PHR1, APA, OsPT2 genes in Tongjing 981 roots was very low under low-P stress. Additionally, the activities of both acid phosphatase (APA) in the tissues of roots and secreted by roots in Yi 2434 increased more significantly than that in Tongjing 981, which is possibly one of the key pathway to confer Yi 2434 higher tolerance to the low-P stress than Tongjing 981.

Key words: rice, low phosphorus stress, gene expression, phosphorus activation, efficient phosphorus absorption

摘要：

研究水稻耐低磷机制,对高效利用土壤磷的水稻品种改良具有重要意义。应用基因芯片和qRT-PCR技术,分析了耐低磷水稻品种仪2434和低磷敏感品种通粳981根系中磷高效吸收和利用相关基因表达对低磷胁迫的应答。水稻叶片磷含量的测定结果表明,低磷胁迫下仪2434的叶片磷含量较对照降幅小,这表明仪2434较通粳981具有更强的磷素吸收利用能力。基因芯片检测结果表明,在低磷胁迫下的仪2434根系中,PHR1、osa-miR399s和SPXs基因的表达诱导、激活磷饥饿信号途径;APA、PAPs、MPE、PA、PEPC和VDAC1、C₄-DT/MAT 等基因的表达诱导,增强有机磷水解酶和有机酸的合成和分泌,促进介质中难溶性磷的活化;OsPT2、OsPT6基因的表达诱导,促进仪2434根系对磷的高效吸收。qRT-PCR检测结果表明,仪2434根系中与磷饥饿信号转导、磷活化、磷高效吸收相关的8个代表性基因(PHR1、SPX、PAP、APA、PEPC、MFS、OsPT2、OsPT6)的表达水平均随低磷处理时间的延长呈逐步增高的趋势;经低磷处理后,所检测的8个基因在仪2434根系中的转录水平均显著高于其在通粳981根系中的转录水平,PHR1、APA、OsPT2在通粳981根系中的表达诱导作用不明显,且仪2434根系组织和根系分泌的酸性磷酸酶活性较通粳981增强更显著,这可能是仪2434较通粳981对低磷胁迫有较高耐性的主要机制之一。

关键词: 水稻, 低磷胁迫, 基因表达, 磷活化, 磷高效吸收