Genome-wide identification of GMP genes in Rosaceae and functional characterization of FaGMP4 in strawberry (Fragaria x ananassa)

Background GDP-D-mannose pyrophosphorylase (GMP) is one of the key enzymes determining ascorbic acid (AsA) biosynthesis. However, little information about GMP genes is currently available for the Rosaceae species, especially in the AsA-riched cultivated octoploid strawberry (Fragaria x ananassa). Objective To identify the all the GMP genes in Rosaceae, as well as the predominant homologues and the role of GMP genes in strawberry AsA accumulation. Methods In the present study, we performed genome-wide identification and comprehensive analysis of the duplicated GMP genes in strawberry and other Rosaceae species by bioinformatics methods, the expression of the GMP genes from cultivated strawberry (Fragaria x ananassa, FaGMP) was specifically analyzed by qPCR. Finally, the FaGMP4 was transiently overexpressed in strawberry to estimate the role of GMP in regulating AsA accumulation in strawberry. Results As results, a total of 28 GMP genes were identified in the five Rosaceae species. The origins of duplication events analysis suggested that most GMP duplications in Rosaceae species were generated from whole genome duplication (WGD). The Ka/Ks ratio suggested that FaGMP genes underwent a stabilization selection. qPCR based expression analysis showed different patterns of FaGMP paralogs during fruit ripening, while FaGMP4 expressed higher in the variety containing higher AsA. Overexpression of FaGMP4 in strawberry significantly enhanced AsA accumulation. Furthermore, the expression of FaGMP4 under the treatment of blue and red light was largely increased in leaves while significantly inhibited in fruit. These results revealed the vital role of FaGMP4 in regulating AsA in strawberry.