Expression of the Rice Arginase Gene OsARG in Cotton Influences the Morphology and Nitrogen Transition of Seedlings

Arginase is the only enzyme capable of producing urea in plants. This enzyme also contributes to many important biological functions during plant growth and development, such as seed development, root development and plant nitrogen using. The unique rice arginase gene OsARG is known to affect nitrogen use efficiency and is also associated with higher yields in rice. In this study, we transformed OsARG into upland cotton R18 by Agrobacterium-mediated genetic transformation and analyzed the function of OsARG in transgenic cotton. Two independent OsARG expression transgenic cotton lines, ARG-26 and ARG-38, were obtained via transformation. Southern blot analysis indicated that two copies and one copy of the OsARG gene were integrated into the ARG-26 and ARG-38 genomes, respectively. Enzyme activity and RNA transcription analysis revealed that the OsARG gene is highly expressed in cotton. The nitric oxide content and the morphology of ARG-26 and ARG-38 seedlings were both affected by expression of the OsARG gene. Field experiments indicated that the polyamine and nitrogen content increased by more than two-fold in the T3 generation plants of the transgenic cotton lines ARG-26-2, ARG-26-7, ARG-38-8, and ARG-38-11, as compared with the control plants. After harvesting cotton fibers grown in field conditions, we analyzed the quality of fiber and found that the fiber length was increased in the transgenic lines. The average cotton fiber length for all of the transgenic cotton lines was two millimeters longer than the fibers of the control plants; the average cotton fiber lengths were 31.94 mm, 32.00 mm, 32.68 mm and 32.84 mm in the ARG-26ARG-26-2, ARG-26-7, ARG-38-8 and ARG-38-11 lines, respectively, but the average fiber length of the control plants was 29.36mm. Our results indicate that the OsARG gene could potentially be used to improve cotton fiber length traits.精氨酸酶（Arginase）是植物体内唯一能够合成尿素的酶类。该酶在植物生长发育过程中参与诸多重要生物学功能，包括种子发育、根系建成以及植物氮素利用等。水稻中独特的精氨酸酶基因OsARG已被证实可影响氮素利用效率，同时与水稻高产性状相关。本研究通过农杆菌介导的遗传转化方法，将OsARG基因导入陆地棉R18品种中，并对该基因在转基因棉花中的功能展开分析。经转化后，我们获得了两个独立的OsARG过表达转基因棉花株系ARG-26与ARG-38。Southern印迹（Southern blot）分析结果显示，OsARG基因分别以2个拷贝和1个拷贝的形式整合至ARG-26与ARG-38的基因组中。酶活性与RNA转录水平分析表明，OsARG基因在转基因棉花中呈现高表达模式。ARG-26与ARG-38幼苗的一氧化氮含量及形态均受到OsARG基因表达的调控。田间试验结果显示，相较于对照植株，转基因棉花株系ARG-26-2、ARG-26-7、ARG-38-8及ARG-38-11的T3代植株中多胺与氮素含量均提升了两倍以上。收获田间种植的棉花纤维后，我们对纤维品质进行了分析，发现转基因株系的纤维长度均有所提升。所有转基因株系的平均纤维长度较对照植株高出2 mm；其中ARG-26-2、ARG-26-7、ARG-38-8及ARG-38-11四个株系的平均纤维长度分别为31.94 mm、32.00 mm、32.68 mm与32.84 mm，而对照植株的平均纤维长度为29.36 mm。本研究结果表明，OsARG基因可用于改良棉花纤维长度性状。