Xanthine dehydrogenase (XDH) is an important enzyme in purine metabolism. It is involved in regulation of the normal growth and non-biological stress-induced ageing processes in plants. The present study investigated XDH’s role in regulating rice leaf senescence. We measured physical characteristics, chlorophyll content and fluorescence parameters, active oxygen metabolism, and purine metabolism in wild-type Kitaake rice (Oryza sativa L.), an OsXDH over-expression transgenic line (OE9), and an OsXDH RNA interference line (Ri3) during different growth stages. The expression patterns of the OsXDH gene confirmed that XDH was involved in the regulation of normal and abiotic stress-induced ageing processes in rice. There was no significant difference between the phenotypes of transgenic lines and wild type at the seedling stage, but differences were observed at the full heading and maturation stages. The OE9 plants were taller, with higher chlorophyll content, and their photosystems had stronger light energy absorption, transmission, dissipation, and distribution capacity, which ultimately improved the seed setting rate and 1000-seed weight. The opposite effect was found in the Ri3 plants. The OE9 line had a strong ability to remove reactive oxygen species, with increased accumulation of allantoin and alantoate. Experimental spraying of allantoin on leaves showed that it could alleviate chlorophyll degradation and decrease the content of H₂O₂ and malonaldehyde (MDA) in rice leaves after the full heading stage. The urate oxidase gene (UO) expression levels in the interference line were significantly lower than those in the over-expression line and wild-type lines. The allantoinase (ALN) and allantoate amidinohydrolase (AAH) genes had significantly higher expression in the Ri3 plants than the in OE9 or wild-type plants, with OE9 plants showing the lowest levels. The senescence-related genes ACD1, WRKY23, WRKY53, SGR, XERO1, and GH27 in Ri3 plants had the highest expression levels, followed by those in the wild-type plants, with OE9 plants showing the lowest levels. These results suggest that enhanced activity of XDH can regulate the synthesis of urea-related substances, improve plant antioxidant capacity, effectively delay the ageing process in rice leaves, and increase rice yield.

黄嘌呤脱氢酶（XDH）是嘌呤代谢中的重要酶。它参与调节植物的正常生长和非生物胁迫诱导的衰老过程。本研究调查了XDH在调节水稻叶片衰老中的作用。我们测量了野生型Kitaake水稻（Oryza sativa L。），OsXDH过表达转基因系（OE9）和OsXDH RNA干扰系（Ri3）的物理特性，叶绿素含量和荧光参数，活性氧代谢和嘌呤代谢）处于不同的成长阶段。OsXDH的表达模式该基因证实XDH参与了正常和非生物胁迫诱导的水稻衰老过程的调控。转基因株系的表型和野生型在苗期没有显着差异，但在抽穗和成熟期却观察到差异。所述OE9植株高，具有更高的叶绿素含量，和它们的光系统具有较强的光能量吸收，透射，耗散，和分配能力，这最终提高了结实率和千粒重。在Ri3植物中发现相反的作用。该OE9该品系具有较强的去除活性氧的能力，并增加了尿囊素和丙氨酸的积累。尿囊素在叶片上的喷雾试验表明，抽穗期后，尿囊素可以减轻叶绿素的降解并降低H ₂ O ₂和丙二醛（MDA）的含量。干扰株中的尿酸氧化酶基因（UO）表达水平明显低于过表达株和野生型株。所述allantoinase（ALN）和尿囊脒基水解酶（AAH）基因在有显著更高的表达RI3植物比在OE9或野生型植物，具有OE9显示最低水平的植物。衰老相关基因ACD1，WRKY23，WRKY53，SGR，XERO1和GH27在RI3植物具有最高的表达水平，其次是野生型植物，具有OE9植物展示的最低水平。这些结果表明，XDH活性的增强可以调节尿素相关物质的合成，提高植物的抗氧化能力，有效地延缓水稻叶片的衰老过程，并提高水稻产量。