MULTIPLE NEP1 ORTHOLOGUES FROM PHYTOPHTHORA MEGAKARYA WERE EXPRESSED DURING THE INFECTION OF THEOBROMA CACAO LEAVES AND NEP1 PROTEIN INDUCES VARIOUS WOUND-RESPONDING GENES IN CACAO LEAVES.

Authors: BAE, HANHONG - USDA/ARS; Bailey, Bryan; Strem, Mary; DE MAYLOLO, GABRIELA - PENN STATE/DPT HORT; GUILITNAN, MARK - PENN STATE/DPT HORT; VERICA, JOSEPH - PENN STATE/DPT HORT; MAXIMOVA, SIELA - PENN STATE/DPT HORT; BOWERS, JOHN - USDA/ARS

Submitted to: BARC Poster Day
Publication Type: Abstract Only
Publication Acceptance Date: 4/29/2004
Publication Date: 4/29/2004
Citation: Bae, H., Bailey, B.A., Strem, M.D., De Maylolo, G.A., Guilitnan, M.J., Verica, J.A., Maximova, S.N., Bowers, J.H. 2004. Multiple nep1 orthologues from phytophthora megakarya were expressed during the infection of theobroma cacao leaves and nep1 protein induces various wound-responding genes in cacao leaves. [abstract]. BARC Poster Day.

Interpretive Summary:

Technical Abstract: The extra-cellular protein NEP1 (necrosis inducing protein) is produced by Fusarium oxysporum f. sp. erythroxyli. NEP1 causes cell death in many different dicot plant species when applied as a foliar spray. Orthologues of NEP1 gene have been identified in a broad range of microbes. In the current study, orthologues of NEP1 gene were cloned and characterized in Phytophthora megakarya, a fungal agent of black pod disease of Theobroma cacao (cacao). In addition, the response of cacao to NEP1 was studied in four developmental stages of cacao leaves: unexpanded (UE), young red (YR), immature green (IG), and mature green (MG). NEP1 changed the expression of eight genes of cacao leaves, which were detected by differential display, and the differential expression was confirmed by RNA blot analyses. TcCAF-1 was most highly expressed in UE leaves, and TcPER-1, TcGLU-1, and TcCOU-1 were most abundant in YR leaves. TcLHCA-1 was highly expressed in IG and MG leaves, and TcWRKY-1 and TcCHIB were most highly expressed in MG leaves. NEP1 (5 ug mL-1 plus 0.2% Silwet-L77) caused necrotic flecks on the under side of MG cacao leaves within 24 hr of foliar application. Necrotic lesions were observed on YR cacao leaves 10 days after NEP1 treatment. Treatment of NEP1 induced four genes (TcWRKY-1, TcORFX-1, TcPER-1, and TcGLU-1) and repressed TcLHCA-1 in MG leaves. Expression of TcWRKY-1 and TcORFX-1 was induced in YR leaves after treatment with NEP1. P. megakarya expressed NEP1 orthologues during a compatible infection of cacao leaves. NEP1 caused necrosis and altered gene expression in cacao leaves, but the response to NEP1 mimicked the response to wounding associated with initiation of the leaf disk assay than induced resistance.