Submitted to: Physiological and Molecular Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/11/2004
Publication Date: 11/20/2005
Citation: Qiu, X., Guan, P., Wang, M., Moore, P.H., Zhu, Y.J., Hu, J., Borth, W., Albert, H.H., 2004. Identification and expression analysis of bth induced genes in papaya. Physiological and Molecular Plant Pathology. 65:21-30. Interpretive Summary: Systemic Acquired Resistance (SAR) is an inducible state of broad-spectrum disease resistance in plants that involves the induction of numerous genes. In a collaborative project involving UH, HARC and ARS researchers, papaya genes induced during SAR were identified and induction levels were determined. Over four biological replicates gene expression measurements were found to be highly reproducible, so that expression changes as low as 1.43-fold induction could be determined with statistical significance (P=0.05). Understanding this phenomenon provides strategies for manipulating the response to produce more highly disease resistant papaya and other crop plants.
Technical Abstract: Suppression subtractive hybridization (SSH) was used to produce a Carica papaya L. cDNA library enriched for benzothiadiazole (BTH) induced genes. From this library 360 clones were screened by reverse-northern dot blot. ESTs found to be BTH-induced by this method were confirmed by northern blot and by quantitative RT-PCR. Quantitative estimates of changes in gene expression were corrected for amplification efficiencies of each amplicon based on the log slope of fluorescence versus cycle number. The 360 screened clones produced 24 unique papaya ESTs with expression altered ' 1.5-fold in at least one assay and 17 of these were significantly changed at P'0.05 over four biological replicates. mRNA for all tested genes was detectable by qRT-PCR; expression data were highly reproducible so expression changes as low as 1.43-fold could be scored significant. These ESTs included homologs of defense-related genes from other species and also several genes for which no defense-related function has been previously described. Genes without known defense related functions include a 4-hydroxyphenylpyruvate dioxygenase and a 2OG-Fe(II) oxygenase.