Ubiquitination in wheat defence against Septoria.

Abstract

Wheat is a major food crop for much of the world, and with an ever-increasing population there is a rising demand to produce more food in a smaller area. Septoria leaf blotch mould (caused by the fungus Septoria) is a devastating foliar pathogen of wheat, which can lead to a 20% reduction in yield.
Plants have had to evolve a multitude of different defence mechanisms due to their sessile nature. Protein modifications by ubiquitination has been shown to be central to plant defence.
Virus Induced Gene Silencing (VIGS) using BSMV (Barley Stripe Mosaic Virus) has been used previously to transiently silence wheat gene expression. In this study VIGS has been used to investigate Triticum aestivum E2 ubiquitin conjugating (TaU) enzymes. The possible function of these TaU enzymes in the Septoria-wheat interaction was investigated after silencing the TaU enzymes in wheat and then infecting with Septoria. TaU4 silenced wheat leaves showed a delay in the onset of Septoria infection symptoms and had reduced pycnidia and spore counts when compared to the vector only control. It was concluded that TaU4 acts as a negative regulator of defence in wheat against Septoria fungal infection. The E2 function of TaU4 has also been proven through ubiquitin charging assays. Four other TaU enzymes were also studied to ascertain their role in wheat defence against Septoria.