OsUreD基因突变对水稻生长及其氮素营养生理的影响

植物细胞中,脲酶活性的存在使得尿素经水解后能够成为可被直接利用的铵态氮。脲酶的活性需要金属镍离子的活化,同时也需要三种脲酶辅助蛋白UreD、UreG及UreF的协同作用。本文对T-DNA插入的水稻脲酶辅助蛋白基因Osured突变体的农艺性状、氮素营养生理以及相关的酶活性变化进行了较详细的研究,结果表明,种子萌发1~7d,Osured突变体中的脲酶活性未发生明显变化,但显著低于野生型约60%~80%;精氨酸酶活性显著增加,高于野生型约30%~40%。在水稻幼苗期和分蘖期,突变体则表现出生长受到抑制而植株矮小(其株高、根长显著低于野生型)、分蘖减少,脲酶活性也明显低于野生型约60%~90%。由此表明,OsUreD的功能对维持水稻正常脲酶活性的必要性;该基因的突变导致植物中脲酶及精氨酸酶活性改变等氮代谢途径的紊乱,可能是突变体水稻生长受阻以及分蘖数减少的重要分子生理学因子。

Impact of OsUreD Mutation on Rice Growth Phenotype and Nitrogen Nutritional Physiology

The existence of urease activity in plant cells makes hydrolize urea into ammonium that can be directly used by the plant. It has been reported that the activity of rice urease needs both the activation by nikel ion and co-ordination of three anncessory proteins i.e. UreD, UreG and UreF. In this work, the agronomic traits, nitrogen nutritional physiology and related enzymes’ activity were investigated in a rice Osured mutant, where Osured was deleted by a T-DNA insertion. This research revaled that during the seed germination of 1~7 d, the urease activity in the mutant remained relatively stable and 60%~80% lower than that of in wildtype (WT), but the activity of arginase increased by 30%~40% as compared to the WT. At the seeding- and tillering-stage, the mutant line exhibited an obvious growth inhibition with being small in size, e.g. lower plant-height and root length, reduction in tiller numbers,and reduced urease activity by 60%~90%. These results suggested that OsUreD encoding protein should be critical for rice urease activation. Nitrogen metabolic disorder associeted with alteration of the activity of urease and arginase in the Osured mutation might be an important molecular physiological factor responsible for the supression of rice growth and tillering.