Transgenic grapefruit plants expressing the PAPETALA3-IPT gp gene exhibit altered expression of PR genes

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 level 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 control of expression of three pathogenesis-related protein genes: b-1,3-glucanase, a stress related PR gene 24P220, and an acidic chitinase, 24P262 was examined. Expression of b-1,3-glucanase, and 24P220 gene were significantly enhanced in transgenic plants while the expression of chitinase was reduced to low levels. Our results confirm the effect of cytokinins on expression of genes implicated in the response of grapefruit plants to pathogen attack and suggest a possible role of cytokinins in pathogen resistance.

Promoters for Transgenic Horticultural Plants

“…Despite the presence of a tissue-specifi c promoter, the expression was not restricted by fl ower tissue. Altered expression of the pathogenesis-related genes in transgenic grapefruit plants suggested a possible role of cytokinins in pathogen resistance (Pasquali et al 2009 ).…”

Improving low-temperature tolerance in sugarcane by expressing the ipt gene under a cold inducible promoter

“…To avoid these problems, endogenous contents of CKs have been increased by creating transgenic plants with increased activity of isopentenyl transferase encoded by the ipt gene (Akiyoshi et al 1984). Cytokinin overproduction in these plants provided lower leaf abscission, maintenance of photosynthetically active leaves (Květoň 2006), delay in flowering (Gan andAmasino 1995, McCabe et al 2001), and increased tolerance to biotic and abiotic stresses (Rivero et al 2007, Swartzberg et al 2008, Pasquali et al 2009). …”

Consequences of transforming narrow leafed lupin (Lupinus angustifolius [L.]) with an ipt gene under control of a flower-specific promoter

“…The ipt gene has also been coupled to heterologous seed storage protein promoters in both tobacco and canola (Röckel et al 1997(Röckel et al , 1998Ma et al 1998;Daskalova et al 2007), and there has been a report of rooted transgenic plants transformed with ipt coupled to a corolla-specific chalcone synthase promoter from snapdragon (Hocart et al 1992). Pasquali et al (2009) coupled ipt to the floral organs-specific APETALA3 promoter from Arabidopsis thaliana in an attempt to obviate systemic increases in CK. Despite the use of tissue-specific promoters in many studies the phenotypes are consistent with enhanced CK levels outside the target organs.…”