Auxin biosynthesis by the YUCCA6 flavin monooxygenase gene in woodland strawberry.

Auxin has been regarded as the main signal molecule coordinating the growth and ripening of fruits in strawberry, the reference genomic system for Rosaceae. The mechanisms regulating auxin biosynthesis in strawberry are largely elusive. Recently, we demonstrated that two YUCCA genes are involved in flower and fruit development in cultivated strawberry. Here, we show that the woodland strawberry (Fragaria vesca L.) genome harbors nine loci for YUCCA genes and eight of them encode functional proteins. Transcription pattern in different plant organs was different for all eight FvYUCs. Functionality of the FvYUC6 gene was studied in transgenic strawberry overexpressing FvYUC6, which showed typical high-auxin phenotypes. Overexpression of FvYUC6 also delayed flowering and led to complete male sterility in F. vesca. Additionally, specific repression of FvYUC6 expression by RNA interference significantly inhibited vegetative growth and reduced plant fertility. The development of leaves, roots, flowers, and fruits was greatly affected in FvYUC6-repressed plants. Expression of a subset of auxin-responsive genes was well correlated with the changes of FvYUC6 transcript levels and free indole-3-acetic acid levels in transgenic strawberry. These observations are consistent with an important role of FvYUC6 in auxin synthesis, and support a main role of the gene product in vegetative and reproductive development in woodland strawberry.

Genome-wide identification and comparative expression analysis of NBS-LRR-encoding genes upon Colletotrichum gloeosporioides infection in two ecotypes of Fragaria vesca.

Anthracnose caused by Colletotrichum spp. is one of the most destructive diseases of cultivated strawberry (Fragaria×ananassa Duchesne) worldwide. The correlation between NBS-LRR genes, the largest class of known resistance genes, and strawberry anthracnose resistance has been elusive. BLAST search in NCBI identified 94 FvNBSs in the diploid genome of strawberry Fragaria vesca, with 67 of the TIR-NBS-LRR type. At least 36 FvNBSs were expressed, with 25% being non-coding genes. Two F. vesca ecotypes, HLJ and YW, showed great variations in both morphological and physiological responses upon C. gloeosporioides infection. qRT-PCR revealed that 5 of the 12 leaf-expressed FvNBSs displaying opposite transcription responses to C. gloeosporioides infection in two ecotypes. These results showed that the transcriptional responses of several FvNBSs were involved in the ecotype-specific responses to C. gloeosporioides in F. vesca. These FvNBSs hold potential in characterizing molecular components and developing novel markers associated with anthracnose resistance in strawberry.