In this study, the disease resistance gene PlWRKY65 was isolated from the leaves of Paeonia lactiflora and analyzed by bioinformatics methods, and the localization of the encoded protein was explored. Quantitative real-time PCR (qRT-PCR) was also used to explore the response of this gene to Alternaria tenuissima. The results showed that the gene sequence contained multiple cis-acting elements involved in the response to hormone signaling molecules belonging to the IIe subgroup of the WRKY family, and the encoded proteins were located in the nucleus. The PlWRKY65 gene has a positive regulatory effect on A. tenuissima infection. After silencing the PlWRKY65 gene via virus-induced gene silencing (VIGS), it was found that the gene-silenced plants were more sensitive to A. tenuissima infection than the wild plants, exhibiting more severe infection symptoms and different degrees of changes in the expression of the pathogenesis-related (PR) genes. In addition, we showed that the endogenous jasmonic acid (JA) content of P. lactiflora was increased in response to A. tenuissima infection, whereas the salicylic acid (SA) content decreased. After PlWRKY65 gene silencing, the levels of the two hormones changed accordingly, indicating that PlWRKY65, acting as a disease resistance-related transcriptional activator, exerts a regulatory effect on JA and SA signals. This study lays the foundation for functional research on WRKY genes in P. lactiflora and for the discovery of candidate disease resistance genes.

Populus wulianensis is an endangered species endemic to Shandong Province, China. Despite the economic and ornamental value of this species, few genomics and genetic studies have been performed. In this study, we performed a relevant analysis of the full-length transcriptome sequencing data of P. wulianensis and obtained expressed sequence tag (EST)-simple sequence repeat (SSR) markers with polymorphisms that can be used for further genetic research. In total, 8.18 Gb (3,521,665) clean reads with an average GC content of 42.12% were obtained. From the corrected 64,737 high-quality isoforms, 42,323 transcript sequences were obtained after redundancy analysis with CD-HIT. Among these transcript sequences, 41,876 sequences were annotated successfully. A total of 23,539 potential EST-SSRs were identified from 16,057 sequences. Excluding mononucleotides, the most abundant motifs were trinucleotide SSRs (47.80%), followed by di- (46.80%), tetra- (2.98%), hexa- (1.58%) and pentanucleotide SSRs (0.84%). Among the 100 designed EST-SSRs, 18 were polymorphic with high PIC values (0.721 and 0.683) and could be used for analyses of the genetic diversity and population structure of P. wulianensis. These full-length transcriptome sequencing data will facilitate gene discovery and functional genomics research in P. wulianensis, and the novel EST-SSRs developed in our study will promote molecular-assisted breeding, genetic diversity and conservation biology research in this species.

Salt stress has become a major environmental problem affecting plant growth and development. Some WRKY transcription factors have been reported to be involved in the salt stress response in plants. However, there are few studies on the involvement of WRKYs in the salt stress response in Rosa rugosa. In this study, we isolated a salt tolerance gene, RrWRKY1, from R. rugosa. RrWRKY1 was found to belong to Group I of the WRKY family, and it was specifically expressed in leaves and petals. RrWRKY1 expression was upregulated under NaCl stress in rose leaves. After silencing RrWRKY1 in R. rugosa, transgenic plants showed dry leaves and black and brown veins, indicating sensitivity to salt stress. At the same time, the transcription levels of the salt tolerance-related genes RrNHX1, RrABF2, RrRD22, RrNCED1, and RrHKT1 also changed significantly. The superoxide dismutase (SOD) and peroxidase (POD) activities decreased, the proline content decreased, and the malondialdehyde (MDA) content in the gene-silenced plants increased, indicating that RrWRKY1 regulates the salt tolerance of R. rugosa. In addition, the overexpression of RrWRKY1 in Arabidopsis thaliana improved the germination rate and the average of the main root and lateral root lengths, and the transgenic plants had a larger number of lateral roots than the WT plants under salt stress. This study provides candidate gene resources for salinity tolerance breeding and a theoretical basis for analyzing the salinity tolerance mechanism of the WRKY gene.