|WALTER, STEPHANIE - University College Dublin|
|KAHLA, AMAL - University College Dublin|
|ARUNACHALAM, CHANEMOUGHASOUN - University College Dublin|
|PEROCHON, ALEXANRE - University College Dublin|
|KHAN, MOIJIBUR - University College Dublin|
|Scofield, Steven - Steve|
|DOOHAN, FIONA - University College Dublin|
Submitted to: Journal of Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/20/2015
Publication Date: 3/1/2015
Citation: Walter, S., Kahla, A., Arunachalam, C., Perochon, A., Khan, M.R., Scofield, S.R., Doohan, F.M. 2015. A wheat ABC transporter contributes to both grain formation and mycotoxin tolerance. Journal of Experimental Botany. 66(9):2583-2593. DOI:10.1093/jxb/erv048.
Interpretive Summary: Fusarium graminearum is the fungus that causes the devastating disease of wheat and barley, Fusarium head blight. This disease not only greatly lowers grain yield and quality, but it causes the grain to become contaminated with a dangerous mycotoxin, deoxynivalenol (DON). Previous work showed that two wheat genes whose expression is stimulated when wheat flowers are treated with DON, likely encode transporter proteins that might remove DON from the wheat cells. This hypothesis was tested using a virus-induced gene silencing system which can turn-off expression of chosen wheat genes. When the genes of interest TaABCC3.1 and TaABC3.2 were turned-off, it was observed that wheat became much more sensitive to DON, which supports their proposed function in DON detoxification. This finding may be useful in developing wheat and barley with less sensitivity to DON or greater resistance to Fusarium head blight, as the action of DON is important for the spreading of the fungus.
Technical Abstract: Deoxynivalenol (DON) is a mycotoxin produced by Fusarium fungi which acts as a disease virulence factor, aiding fungal pathogenesis of cereals spikelets and spread of the economically important Fusarium head blight (FHB) disease. Previously, a fragment of a wheat ABC transporter gene was shown to be associated with the DON resistance at the gene expression level. Here, we describe the cloning and functional characterisation of this gene, TaABCC3.1, as well as of its homolog (TaABCC3.2). The respective genes encode proteins of 1500 and 1497aa, respectively, which shared 97% identity. Analysis of their structural domains, phylogeny and predicted 3D structures evidenced that both represent typical full-length ABC family C transporters. PCR-based mapping and genome analysis located TaABCC3.1 to the short arm of wheat chromosome 3B, but not to the FHB resistance QTL Fhb1. Virus-induced gene silencing of the expression of both TaABCC3 genes (using two independent gene-specific constructs) demonstrated that the respective encoded wheat ABCC proteins contribute to wheat resistance to DON. Gene silencing resulted in > X% more toxin-induced bleaching in wheat spikelets as compared to in non-silenced spikelets (P). The efficacy of silencing was verified by real time RT-PCR analysis of gene expression (>X-fold less transcript in DON-treated spikelets of gene-silenced as compared in in empty vector treated plants; P). Gene expression studies indicate that TaABCC3.1 is part of the early host response to DON and that activation of TaABCC3.1 expression is not just a secondary effect of the toxins primary mode of action (i.e. inhibition of the elongation step in protein synthesis). At the transcriptional level, TaABCC3.1 was also responsive to the defence hormone jasmonic acid, a key hormone in host resistance to FHB disease. Thus TaABCC3.1 is a promising target to enhance wheat resistance to DON and Fusarium diseases. Being a native wheat gene, it is an ideal target for traditional wheat breeding approaches that aim to improve disease resistance.