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Effect of nitrogen on the expression of nod genes in Rhizobium astragali (R. huakuii)

Gao Bingli, Yang Guoping, Chen Yongxuan, Shen Sishi, You Zhipeng, Jin Runzhi

Department of Microbiology,Nanjing Agricultural University.Nanjing 210095,Jiangsu；China

Abstract

Secretion of Nod factor which caused host root hair deformation (Had phenotype) could be inhibited by ammonium sulfate at high concentration in Rhizobium astragali (R. huakuii). Other combined forms of nitrogen such as potassium nitrate, urea and Asp had a small effect on the expression of nod genes. Nodulation of Rhizobium astragali could also be repressed by ammonium sulfate (2mmol/L) in Astragalus sinicus plants. By assaying for #beta#-galactosidase activity of nodA-lacZ, nodBC-lacZ, nodD1-lacZ and nodD2-lacZ fusion, we had found that high concentration of ammonium sulfate could repress the expression of nodD2, nodA and nodBC. The authors demonstrated that the expression of the common nodulation genes nodABC of R. astragali which determine early response functions to plant host signals and the regulatory gene nodD2 might be under the control of the level of combined nitrogen (NH~(+)_(4)).

Key words: Nitrogen;Rhizobium astragali;nod genes;Repressin

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Citing This Article：

Gao Bingli, Yang Guoping, Chen Yongxuan, Shen Sishi, You Zhipeng, Jin Runzhi. Effect of nitrogen on the expression of nod genes in Rhizobium astragali (R. huakuii). Acta Physiol Sin 1997; 49 (4): (in Chinese with English abstract).