Yun-Zhe XU1,2, Rui-Lin YOU2, and Nai-Hu WU*
(¹Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100080, China;
2College of Life Sciences, Peking University, Beijing 100871, China)

Abstract The osRACD gene correlated with fertility transformation in the photoperiod sensitive genic male sterile rice (PGMR), Nongken 58S, encoded a rice (Oryza sativa L. ssp. japonica) small GTPase belonging to the Rac/Rho family. Inverse PCR was performed to amplify a fragment about 1.4 kb in 5' upstream region of the osRACD promoter. Deletion mutation and gel mobility shift assay characterized two fragments (-799 to -686 nt, and -686 to -431 nt) in the osRACD promoter that could be involved in its transcriptional regulation. When these two deletion fragments were used as probe respectively, a retarded band appeared in the nuclear extracts of fertile 58S rice under short day (58S-SD). Whereas no retarded band was shown in the nuclear extracts of sterile 58S rice under long day (58S-LD). Competition assay indicated that the factors in the retarded bands binding to these two fragments were the same trans-acting factor (termed rice factor, RF). The binding affinity of RF was affected by phosphorylation and was higher in SD-growth rice than that of LD-growth rice.

Key words photoperiod-sensitive male genic sterile rice; osRACD gene; photoperiod fertility transformation; cis-element

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Received: October 23, 2003 Accepted: January 15, 2004
This work was supported by the grants from the Transgenic Plant Research Project of Ministry of Science and Technology (J00-A005), the Major State Basic Research Development Program of China (2001CB1088) and the National High Technology Research and Development Program of China (20002A224061)
*Corresponding author: Tel, 86-10-82610114; E-mail, nhwu@public3.bta.net.cn