Genome-wide identification of thaumatin-like protein family genes in Panax notoginseng and analysis of their responses to Fusarium solani infection

Panax notoginseng (Burke) F. H. Chen, which is commonly referred as ''Sanqi'', is the most widely used Chinese medicinal herb. Root rot can have deleterious effects on the success of Sanqi cultivation, including reductions in yield and quality. Thaumatin-like proteins (TLPs) are large, complex proteins in the pathogenesis-related family 5 (PR-5) that play key roles in the responses of plants to environmental stress (e.g., pathogen infection) and other physiological processes. The aim of this study was to identify the TLP gene family members in the genome of Sanqi and characterize their responses to Fusarium solani infection. A total of 20 PnTLP genes were identified in the Sanqi genome, which were phylogenetically divided into 10 subfamilies (Group I-X). Subcellular localization analysis revealed that most of the PnTLP proteins were in the extracellular space, while a few located in chloroplasts. MEME Suite software was used to characterize the structure of PnTLP genes and identify the conserved domains of PnTLP proteins. Analysis of gene duplications revealed that segmental duplication has played a key role in driving the expansion of the PnTLP family. Analysis of collinear relationships revealed 36 homologous genes between Sanqi and Arabidopsis and nine homologous genes between Sanqi and rice. Prediction of the cis-acting elements of the promoters of PnTLP genes indicated that PnTLP genes are involved in biotic, abiotic stress, and hormone induction. Analysis of expression profiles revealed that TLP genes are involved in plant development and the response of plants to fungal infection. qRT-PCR analyses indicated that the expression of PnTLP genes was up-regulated or down-regulated in response to F. solani infection. The results of this study provide new insights on PnTLP genes and their potential roles in the responses of plants to pathogenic fungi. Additional research may be necessary to clarify the role of PnTLP genes identified in our study in disease resistance.