| Summary: | During the infection of grapevine (<i>Vitis vinifera</i>) by the fungus <i>Botrytis cinerea</i>, the concentration of polyamines, which are toxic substances for the phytopathogen, increases in the grape. Nine NRPS genes have been identified in the genome of <i>B. cinerea</i>, yet the function of five of them remains unknown. For this reason, we have studied the expression of the 9 NRPS genes by RT-qPCR in a medium supplemented with sublethal concentrations of three polyamines (1,3-diaminopropane (1,3-DAP), spermidine (SPD), and spermine (SPM)). Our results show that the presence of polyamines in the culture medium triggered the overexpression of the <i>Bcnrps</i>1 gene in the pathogen. Deleting <i>Bcnrps</i>1 did not affect mycelial growth or adaptation to osmotic stress, and we show that its expression is not essential for the cycle of infection of the <i>B. cinerea</i>. However, mutating the <i>Bcnrps</i>1 gene resulted in overexpression of the <i>Bcnrps</i>6 gene, which encodes for the excretion of siderophores of the coprogen family. Moreover, gene deletion has reduced the tolerance of <i>B. cinerea</i> B05.10 to toxic substances such as the polyamine SPD and the fungicide pyrimethanil, and its virulence has increased. Our findings provide new insights into the function of the <i>Bcnrps</i>1 gene and its involvement in the tolerance of <i>B. cinerea</i> against exogenous toxic compounds.
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