PlWRKY 13 : A transcription factor involved in abiotic 2 and biotic stress responses in Paeonia lactiflora 3

To study the function of the WRKY family in peony, the PlWRKY13 gene (KY271095) was 12 cloned from peony leaves. The sequence analysis and subcellular localization results revealed that 13 PlWRKY13 has no introns, belongs to the type IIc subgroup of the WRKY family, and functions in 14 the nucleus. The expression pattern of PlWRKY13 was analysed by semi-quantitative RT-PCR and 15 real-quantitative RT-PCR (qRT-PCR), which showed that the expression of PlWRKY13 was the 16 highest in the medial petals and buds, but was nearly absent in the roots. PlWRKY13 was induced 17 by four abiotic stresses, low-temperature, high-temperature, waterlogging and salt stress, and was 18 positively regulated in response to these stresses. In addition, the expression of PlWRKY13 tended 19 to first decrease and then increase after infection with Alternaria tenuissima. Virus-induced gene 20 silencing (VIGS) technology was used to further explore its function in the resistance of P. lactiflora 21 to fungal infection, and the results showed that PlWRKY13-silenced plants had increased sensitivity 22 to A. tenuissima. The infection was more serious and the disease index (DI) was significantly higher 23 in the PlWRKY13-silenced plants than in the control plants, and the expression of pathogenesis24 related (PR) genes was also significantly changed in PlWRKY13-silenced plants compared with the 25 control plants. The determination of the two endogenous hormones jasmonic acid (JA) and salicylic 26 acid (SA) showed that the JA content increased gradually after infection with A. tenuissima and that 27 JA may play an active role in the resistance of P. lactiflora to pathogen infection, while the SA content 28 decreased after PlWRKY13 silencing. The contents of the two hormones decreased overall, 29 suggesting that the contents of the two hormones are related to the transcription level of PlWRKY13 30 and that PlWRKY13 may be involved in the disease-resistance pathway mediated by JA and SA. In 31 summary, our study showed that PlWRKY13 expression was induced by stress and had a positive 32 effect on the resistance of P. lactiflora to fungal infection. 33