Publications - Faculty - Recently Submitted Faculty Publications 2008

Orbovic - Journal of Experimental Botany

Transgenic grapefruit plants expressing PAPETALA3-IPTgp gene exhibit altered expression of PR-protein genes 

Pasquali G., V. Orbović, and J.W. Grosser

Abstract. Transgenic grapefruit plants (Citrus paradisi cv. ‘Duncan’) with the isopentenyltransferase (ipt) gene under the control of APETALA3 promoter have been produced using Agrobacterium-mediated transformation. The relative expression of the ipt gene was between 2.3 and 7 times higher in transformed plants than in the wild-type but despite the presence of a tissue-specific promoter, the expression was not limited only to flower tissue. Increased levels of trans-zeatin riboside between 9.4 and 32 fold found in transgenic grapefruit were considered the consequence of ectopic expression of the ipt gene. Chlorophyll levels in fully expanded uppermost leaves were also about 30% higher in transgenic than in wild-type plants. Involvement of cytokinins in pathogen resistance was examined through expression of three pathogenesis related protein genes: β-1,3-glucanase, a stress-related PR protein gene 24P220,  and an acidic chitinase, 24P262. Expression of β-1,3-glucanase, and 24P220 gene were significantly enhanced in transgenic plants while the expression of chitinase was reduced to low levels. Our results are consistent with the role of cytokinins in the mediation of the response of grapefruit plants to pathogen attack.