In the growth and development of plants, some non-coding small RNAs (sRNAs) not only mediate RNA interference at the post-transcriptional level, but also play an important regulatory role in chromatin modification at the transcriptional level. In these processes, the protein factors Argonaute (AGO), Dicer-like (DCL), and RNA-dependent RNA polymerase (RDR) play very important roles in the synthesis of sRNAs respectively. Though they have been identified in many plants, the information about these gene families in strawberry was poorly understood. In this study, using a genome-wide analysis and a phylogenetic approach, 13 AGO, six DCL, and nine RDR genes were identified in diploid strawberry Fragaria vesca. We also identified 33 AGO, 18 DCL, and 28 RDR genes in octoploid strawberry Fragaria × ananassa, studied the expression patterns of these genes in various tissues and developmental stages of strawberry, and researched the response of these genes to some hormones, finding that almost all genes respond to the five hormone stresses. This study is the first report of a genome-wide analysis of AGO, DCL, and RDR gene families in Fragaria spp., in which we provide basic genomic information and expression patterns for these genes. Additionally, this study provides a basis for further research on the functions of these genes and some evidence for the evolution between diploid and octoploid strawberries.

Strawberry (Fragaria ananassa) is a widely grown horticultural crop, which exists in red, yellow, and white varieties. In recent years, the white-fleshed strawberry variety is gaining more attention from consumers for its unique taste and appearance, but a comprehensive understanding of the molecular processes governing the ripening of white-fleshed strawberry remains undisclosed. In this study, based on the joint analysis of physiology, metabolome, and transcriptome, we screened and identified the key metabolites that were highly correlated to the maturation of white-fleshed strawberry (cv. ‘snow white’, SW for short) fruits. In contrast to red-fleshed strawberries, SW fruits exhibited three main ripening stages during the maturation, accompanied by the increases in total soluble solid and total sugar and the declines in total anthocyanin and total acid. Metabolomic analysis identified 832 differential accumulated metabolites (DAMs) at the secondary level of LC-MS/MS, and further investigations suggested that the increase in sucrose, citric acid, and epicatechin levels potentially play a role in the ripening process of SW fruits. Furthermore, abscisic acid and methyl jasmonate were recognized as the primary phytohormones involved in the production of these metabolites. The enrichment analysis of RNA-Seq data revealed that the differential expressed genes (DEGs) were primarily attributed to the pathways of ‘Starch and sucrose metabolism’ and ‘Plant hormone signal transduction’ but were undetected in ‘Flavonoid biosynthesis’ at the late ripening stage. Moreover, the de novo biosynthesis pathway, WGCNA, and Pearson correlation analysis indicated a direct relationship between FaSPS1, FaSPP1, and FaSPP2 with sucrose, FaPEPC1, FaV-PPase2, and FaV-PPase3 with citric acid, and Fa4CL2, Fa4CL3, and FaANR1 with anthocyanin. Further analysis revealed a co-expression of MYBs, bHLHs, NACs, and WRKYs with the structural genes mentioned. Overall, our findings uncovered a molecular mechanism regulating the maturation of white-fleshed strawberry, providing valuable insights for enhancing the flavor of white-fleshed strawberry through the gene-editing technique.