Overexpression of Brassica napus NPR1 enhances resistance to Sclerotinia sclerotiorum in oilseed rape

Sclerotinia sclerotiorum causes a devastating disease in oilseed rape (Brassica napus), an important oil crop, resulting in huge economic losses. Studies have shown that Arabidopsis thaliana NONEXPRESSOR OF PATHOGENESIS-RELATED GENES 1(NPR1), a key regulator of salicylic acid (SA) signaling, plays an important role in plant defense against pathogens. However, little is known about the B. napus (Bna) NPR1 gene and its role in defense to S. sclerotiorum. In this study, we cloned a new NPR1 homolog (BnaNPR1) from B. napus. The new cloned BnaNPR1 exhibits 68.35% identity with AtNPR1 in protein level, and its expression is strongly activated by the SA treatment that, in turn, can enhance resistance to S. sclerotiorum. Further, transgenic Nicotiana benthamiana and B. napus overexpressing BnaNPR1 showed significantly enhanced resistance to S. sclerotiorum. Further experiments showed that after S. sclerotiorum infection, transgenic plants activated the expression of genes associated with SA defense response but suppressed genes associated with JA signaling. These results indicated that BnaNPR1 plays a positive role in resistance of B. napus against S. sclerotiorum, which provides molecular evidence about the positive role of SA signaling in this resistance. Interestingly, it was revealed that the induced expression of BnaNPR1 is suppressed during the S. sclerotiorum infection. Thus, we propose that the strategies for utilization of BnaNPR1 to improve resistance to S. sclerotiorum will be overexpression.