Fusarium head blight evaluation in wheat transgenic plants expressing the maize b-32 antifungal gene

Abstract

The maize gene b-32, normally expressed in the maize (Zea mays) endosperm, encodes for a RIP (Ribosome Inactivating Protein) characterised by antifungal activity. Transgenic wheat plants were obtained via biolistic transformation, in which the b-32 gene is driven by the 35SCaMV promoter in association with the bar gene as a selectable marker. Plants were brought to homozygosity through genetic analysis of progeny and pathogenicity tests were performed on the fourth generation. Six homozygous b-32 wheat lines were characterised. All plants had a normal phenotype, not distinguishable from the control cv. Veery except for slightly smaller size, flowered and set seeds. Western blot analyses confirmed b-32 expression during the plant life cycle in the various tissues. Each line differed in the b-32 content in leaf protein extracts and the transgenic protein expression level was maintained at least up to 10 days after anthesis. Pathogenicity tests for Fusarium head blight (FHB) were performed on the b-32 transgenic wheat lines in comparison to the parental cv. Veery. Resistance to FHB was evaluated by the single floret injection inoculation method on immature spikes with spores of Fusarium culmorum. In all the transgenic lines, a similar reduction in FHB symptoms, not dependent on the level of b-32 protein, has been observed (20% and 30% relative to the control, respectively 7 and 14 days after inoculation). Percentage of tombstone kernels at maturity was also recorded; in all transgenic lines disease control for this parameter was around 25%. The data obtained indicate that maize b-32 was effective as in vivo antifungal protein reducing FHB symptoms in wheat lines expressing the maize RIP protein.

Conferred resistance to Botrytis cinerea in Lilium by overexpression of the RCH10 chitinase gene

“…This analysis has been conducted using an in vitro assay; however, other researchers have found differences in the level of resistance shown by transgenic plants tested in vitro and in vivo such as potato, wheat and barley (Wu et al 1995;Rommens and Kishore 2000;Anand et al 2003;Balconi et al 2007;Shin et al 2008). The next step is therefore to test these transgenic lines under varying conditions in which wind, temperature and humidity fluctuations, nutrient levels in the plant and the interaction with other potential pathogens could have an impact on the level of resistance.…”

Cereal resistance to Fusarium head blight and possibilities of its improvement through breeding

“…Nevertheless, a few studies on the improvement of FHB resistance via transgenosis have already been published, e.g. Balconi et al (2007), who introduced maize antifungal gene b-32 under CaMV 35S promoter into the wheat cultivar Veery and obtained transgenic plants with enhanced Type II and Type III resistance and reduced level of kernel shattering. Other work published by Chen et al already in 1999 reported enhanced resistance in the wheat cultivar Bobwhite expressing a thaumatin-like protein from rice.…”

Antimicrobial peptides

“…Though it has been reported that the degree of antimicrobial activity is not dependent on the AMP production level in transgenic plants, 106 most of the publications furnish clear evidence for peptides' doseeffect activity. 82,100,107,108 Some investigators emphasize the possibility of synergism among different AMPs.…”

“…Undesirably, application of AMPs to engineer pathogen resistance in plants suffers from some limitations, namely species-and race-specificity of the peptides, 120 slight enhanced resistance, 106 induction of infertility, 121 and leakage of conferred resistance after a while due to resiliency of disease-causing microbes. 38 To alleviate these drawbacks as well as to increase the antimicrobial potency of existing peptides, several approaches have been proposed to follow.…”