Submitted to: International Congress of Plant Pathology Abstracts and Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 2/2/2003
Publication Date: 4/4/2003
Citation: Qui, X., Zhu, Y.J., Wang, M.L., Ming, R., Moore, P.H., Gonsalves, D., Albert, H.H. 2003. Isolation and characterisation of genes involved in papaya (Carica papaya l.) systemic acquired resistance. International Congress of Plant Pathology Abstracts and Proceedings. v.2, P12.3. p.169. Interpretive Summary: ABSTRACT ONLY
Technical Abstract: Systemic acquired resistance (SAR) of plants is the result of activation of latent resistance mechanisms that are expressed upon challenge inoculation with a pathogen or a signal chemical such as Salicylic acid (SA), 2,6-dichloroisonicotinic acid (INA), or benzo(1,2,3) thiadiazole-7-carbothioic acid S-methyl ester (BTH). Activation of SAR correlates with the accumulation of highly soluble and reactive proteins called pathogenesis-related (PR) proteins. We are characterising papaya SAR by monitoring the expression of papaya PR genes. We used RT-PCR with degenerate primers to the PR-1 conserved peptide sequence, GHYTQVW, to isolate four partial cDNA clones of PR-1 like genes. One of these, designated PR-1A, was strongly induced by BTH. We constructed a SAR subtraction cDNA library and cloned the genes that were upregulated by BTH. From 26 randomly chosen clones, seven were confirmed by Northern blot analysis to be upregulated by BTH. These seven clones include cDNAs for chitinase, peroxidase, and cytochrome 450. In addition, we cloned and characterised NPR1, a critical component between sensing the pathogen inoculation and the induction of PR genes. Our papaya NPR1 has an ankyrin repeat region and a possible nuclear localisation sequence, both of which are essential for NPR1 function in Arabidopsis. The deduced amino acid sequence of our papaya NPR1 homolog shares 71.0% amino acid similarity with rice and 66.8% with Arabidopsis. We will report our research to overexpress NPR1 in transformed papaya in attempts to increase disease resistance in this crop.