Development of wheat scab symptoms is delayed in transgenic wheat plants that constitutively express a rice thaumatin-like protein gene

The possibility of controlling wheat scab (caused by Fusarium graminearum Schw.) was explored by engineering wheat plants for constitutive expression of pathogenesis-related (PR) protein genes. A rice thaumatin-like protein (TLP) gene (tlp) and a rice chitinase gene (chi11) were introduced into the spring wheat cultivar 'Bobwhite' by co-transformation of the plasmids pGL2ubi-tlp (ubiquitin/tlp//CaMV 35S/hpt) and pAHG11 (CaMV 35S/chi11//ubiquitin/bar). The transformation was by biolistic bombardment. Bialaphos was used as the selection reagent. The integration and expression of the tlp, bar, chi11 and hpt genes were analyzed by Southern, Northern and Western blot analyses. The four transgenes co-segregated in the T₁ progeny of the transgenic plant and were localized at the telomeric region of the chromosome 6A long arm by sequential N-banding and fluorescent in situ hybridization (FISH) using pAHG11 or pGL2ubi-tlp as the probes. Only the transgenes tlp and bar, under the control of the ubiquitin promoter-intron, were expressed. No expression of the chi11 and hpt genes, controlled by the CaMV 35S promoter, was detected in T₁ plants. After inoculation with conidia of F. graminearum, the symptoms of scab developed significantly slower in transgenic plants of the T₁, T₂ and T₃ generations expressing the tlp gene than in non-transformed control plants. This is the first report of enhanced resistance to F. graminearum in transgenic wheat plants with constitutive expression of TLP.