Han Ruicai, He Xunfeng, Pan Xiaohua, Shi Qinghua, Wu Ziming
Key Laboratory of Crop Physiology, Ecology and Genetic Breeding, Ministry of Education, College of Agronomy, Jiangxi Agricultural University, Nanchang, China.
Rice Research Institute, Jiangxi Academyof Agricultural Sciences/Jiangxi Provincial Key Laboratory for Physiology and Genetics of Rice, Nanchang, China.
Rice (N Y). 2020 Mar 11;13(1):16. doi: 10.1186/s12284-020-00375-7.
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 HO 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）是嘌呤代谢中的一种重要酶。它参与植物正常生长和非生物胁迫诱导的衰老过程的调控。本研究调查了XDH在调控水稻叶片衰老中的作用。我们在不同生长阶段测量了野生型 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、活性氧代谢以及嘌呤代谢。OsXDH 基因的表达模式证实 XDH 参与了水稻正常和非生物胁迫诱导的衰老过程的调控。转基因系和野生型在幼苗期的表型没有显著差异，但在齐穗期和成熟期观察到了差异。OE9 植株更高，叶绿素含量更高，其光合系统具有更强的光能吸收、传递、耗散和分配能力，最终提高了结实率和千粒重。在 Ri3 植株中发现了相反的效果。OE9 系具有很强的清除活性氧的能力，尿囊素和尿囊酸的积累增加。实验性地在叶片上喷施尿囊素表明，它可以减轻齐穗期后水稻叶片中叶绿素的降解，并降低 HO 和丙二醛（MDA）的含量。干扰系中的尿酸氧化酶基因（UO）表达水平显著低于过表达系和野生型系。尿囊素酶（ALN）和尿囊酸脒基水解酶（AAH）基因在 Ri3 植株中的表达显著高于 OE9 或野生型植株，OE9 植株的表达水平最低。Ri3 植株中与衰老相关的基因 ACD1、WRKY23、WRKY53、SGR、XERO1 和 GH27 的表达水平最高，其次是野生型植株，OE9 植株的表达水平最低。这些结果表明，XDH 活性增强可调控尿素相关物质的合成，提高植物抗氧化能力，有效延缓水稻叶片衰老过程，并提高水稻产量。
