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Ectopic Expression of the Rice Lumazine Synthase Gene Contributes to Defense Responses in Transgenic Tobacco

June 2010 , Volume 100 , Number  6
Pages  573 - 581

Tingquan Wu, An Guo, Yanying Zhao, Xiaomeng Wang, Ying Wang, Dan Zhao, Xiaojie Li, Haiying Ren, and Hansong Dong

Plant Growth and Defense Signaling Laboratory, Group of Key Laboratory of Monitoring and Management of Crop Pathogens and Insect Pests, Ministry of Agriculture, P. R. China, Nanjing Agricultural University, Nanjing 210095, China.

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Accepted for publication 3 January 2010.

Lumazine synthase (LS) catalyzes the penultimate reaction in the multistep riboflavin biosynthesis pathway, which is involved in plant defenses. Plant defenses are often subject to synergistic effects of jasmonic acid and ethylene whereas LS is a regulator of jasmonic acid signal transduction. However, little is known about whether the enzyme contributes to defense responses. To study the role of LS in plant pathogen defenses, we generated transgenic tobacco expressing the rice (Oryza sativa) LS gene, OsLS. OsLS was cloned and found to have strong identity with its homologues in higher plants and less homology to microbial orthologues. The OsLS protein localized to chloroplasts in three OsLS-expressing transgenic tobacco (LSETT) lines characterized as enhanced in growth and defense. Compared with control plants, LSETT had higher content of both riboflavin and the cofactors flavin mononucleotide and flavin adenine dinucleotide. In LSETT, jasmonic acid and ethylene were elevated, the expression of defense-related genes was induced, levels of resistance to pathogens were enhanced, and resistance was effective to viral, bacterial, and oomycete pathogens. Extents of OsLS expression correlated with increases in flavin, jasmonic acid, and ethylene content, and correlated with increases in resistance levels, suggesting a role for OsLS in defense responses.

© 2010 The American Phytopathological Society