Antisense Suppression of Deoxyhypusine Synthase in Tomato Delays Fruit Softening and Alters Growth and Development

Abstract

The effects of suppressing deoxyhypusine synthase (DHS) have been examined in tomato (Solanum lycopersicum cv UCT5). DHS mediates the first of two sequential enzymatic reactions that activate eukaryotic translation initiation factor-5A (eIF-5A) by converting a conserved Lys to the unusual amino acid, deoxyhypusine. DHS protein levels were suppressed in transgenic plants by expressing the 3#-untranslated region of tomato DHS under regulation of the constitutive cauliflower mosaic virus promoter. Fruit from the transgenic plants ripened normally, but exhibited delayed postharvest softening and senescence that correlated with suppression of DHS protein levels. Northern-blot analysis indicated that all four gene family members of tomato eIF-5A are expressed in fruit, and that three are up-regulated in parallel with enhancement of DHS mRNA as the fruit begin to senesce and soften. Transgenic plants in which DHS was more strongly suppressed were male sterile, did not produce fruit, and had larger, thicker leaves with enhanced levels of chlorophyll. The activity of PSII was 2 to 3 times higher in these transgenic leaves than in corresponding leaves of wild-type plants, and there was also enhanced deposition of starch in the stems. The data collectively indicate that suppression of DHS has pleiotropic effects on growth and development of tomato. This may, in turn, reflect the fact that there is a single DHS gene in tomato and that its cognate protein is involved in the activation of four distinct isoforms of eIF-5A.

The guanylhydrazone CNI-1493: an inhibitor with dual activity against malaria—inhibition of host cell pro-inflammatory cytokine release and parasitic deoxyhypusine synthase

“…While hypusine modification of eIF-5A supports its role in cell proliferation, tissue transglutaminases lead to a γ-glutamyl-hypusine modification in eIF-5A and subsequently to apoptosis (Caraglia et al 2003). Similar observations were made with DHS-suppressed tomato plants showing induced senescence (Wang et al 2005) because of a reduced eIF-5A biosynthesis.…”

Homospermidine in transgenic tobacco results in considerably reduced spermidine levels but is not converted to pyrrolizidine alkaloid precursors

“…One well-characterized function of spermidine is that it acts as a donor of an aminobutyl moiety for the DHS-catalyzed posttranslational activation of the eIF5A protein (Ober and Hartmann 1999a;Park et al 1993). Although the precise mode of action for activated eIF5A is not well understood, it is involved in various plant processes such as seed germination (Moll et al 2002), senescence and apoptosis (Hopkins et al 2007;Thompson et al 2004;Wang et al 2005). In yeast, eIF5A has been shown to be essential for cell proliferation (Park et al 1998), probably by facilitating the translation of certain mRNAs that are required for the cell cycle (Chatterjee et al 2006;Jin et al 2003).…”

RceIF5A, encoding an eukaryotic translation initiation factor 5A in Rosa chinensis, can enhance thermotolerance, oxidative and osmotic stress resistance of Arabidopsis thaliana

“…Suppression of DHS exhibits delayed natural senescence (Duguay et al 2007;Wang et al 2003;Wang et al 2005), indicating that eIF5A is involved in programmed cell death (PCD). There are three isoforms of eIF5A in Arabidopsis thaliana (Thompson et al 2004;Wang et al 2003).…”