Impact Of The Function Of Rice Urease Accessory Protein Gene OsUreG On Plant Growth And Nitrogen Nutritional Physiology

Nitrogen(N)is the most important nutrient and a limiting factor for achieving a higher rice-grain yield.However,the use efficiency of N by rice plant has been estimated to be only about 40% or even less.Thus,exploration and understanding of biological processes involved in uptake and utilization of N-containing compounds/substances should be helpful for increasing the potential of rice to use N effectively.Urea is an important N fertilizer in agriculture and also a critical intermediate in N metabolisms in plant cells;on the other hand,the hydrolytic process of urea by urease into ammonium in the cytosol is of a crucial physiological significance for plant growth and development.It has been reported that the activity of rice urease requires nickel ion and the co-ordination of three accessory proteins i.e.UreD,UreG and UreF.In this study,we designed and conducted experiments to appreciate the influence of OsureG function on the plant growth and nitrogen use physiology,yielding major results summarized as below:1.A T-DNA inserted Osureg mutant was successfully identified and isolated based on the search of rice mutant bank.Furthermore,a homozygous mutant plant was confirmed by PCR test using gene specific and T-DNA primers.Moreover,RT-PCR analysis showed that OsureG gene was not expressed at mRNA level in the Osureg mutant.In addition,Tail-PCR measurement affirmed that only one T-DNA was inserted in the genome of the Osureg mutant rice,suggesting that this Osureg mutant line could be adopted as suitable plant material available for investigating OsureG function.2.When cultivated with a supply of different nitrogen sources,growth phenotyping and physiological measurements related to plant nitrogen nutrition showed that the rice mutant displayed a stunted growth rate with characteristics of e.g.significantly lower biomass and shorter root length as well as c.70% reduction of urease activity,as compared to wild type plants.3.To understand the molecular function of OsureG in plant growth,overexpression lines of Arabidopsis transformed with rice OsureG were created and their molecular physiological role(s)in relation to e.g.nitrogen nutrition was analyzed.Our data showed that the transgenic plants exhibited more leaves and branches as well as higher dry biomass then the wild type.Taken together,our results from the present study suggest that OsureG-coding protein UreG may play critical molecular physiological roles in the maintenance of plant urease activity,nitrogen metabolism as well as plant growth and development.A deeper investigation and understanding of biological functions of this gene is expected to provide valuable fundamental knowledge,helping us explore novel strategy toward the improvement of effective nitrogen use by crops.