A COI1 gene in wheat contributes to the early defence response against wheat powdery mildew.

Abstract: The hormone jasmonate (JA) signalling pathway is involved in diverse developmental processes in plants. COI1 is a key regulator in JA pathway. Although COI1 homologous proteins have been identified in a variety of crops, their regulatory mechanisms in wheat defence responses remain unknown. Here, we cloned <italic>COI1</italic> from disease resistant wheat Brock, designated <italic>TaCOI1</italic>. <italic>TaCOI1 </italic>cDNA was 1988‐bp long, with an ORF encoding 593 deduced amino acids. The phylogenetic tree showed that TaCOI1 was clustered in the same clade of monocotyledons. The predicted protein possesses an F‐box domain, several LRRs and a conserved AMN1 domain. Its transcription was induced in the compatible and incompatible wheat by <italic>Blumeria graminis f. sp. tritici</italic> (<italic>Bgt</italic>) fungus, with differences observed in response time. Expression pattern analysis in the susceptible wheat variety Jing411 revealed that <italic>TaCOI1</italic> was up‐regulated after <italic>Bgt</italic> inoculation at 12‐hour postinoculation (hpi). While, in Brock its transcription was rapidly induced and reached a first peak at 2 hpi. These results suggest that <italic>TaCOI1</italic> may be involved in the early response to powdery mildew. The expression of <italic>TaCOI1</italic> was decreased by virus‐induced gene silencing. The rate of successful penetration by <italic>Bgt</italic> was higher in all <italic>TaCOI1</italic>‐silenced Brock, while the percentage of macrocephalic appressoria and resistance reactions was lower than control. These results suggest that silencing of the <italic>TaCOI1</italic> gene increased Brock susceptibility to infection. Together, these findings indicate that the <italic>TaCOI1</italic> gene could be involved in the early defence response against wheat powdery mildew and may play an important role in wheat–<italic>Bgt</italic> interactions. [ABSTRACT FROM AUTHOR]