Roles of auxin biosynthesis by the flavin monooxygenase genes in developmental control and environmental responses in strawberry

Abstract
Auxin has been regarded as the main signal molecule coordinating the growth and ripening of fruits in strawberry, the reference genomic system for Rosaceae. Functional information regarding the key regulators of auxin biosynthesis during both vegetative and reproductive development and environmental responses is scarce in strawberry. We have isolated and characterized whole YUCCA family genes encoding the key enzyme for auxin biosynthesis in both diploid strawberry (Fragaria vesca) and octoploid strawberries (F. × ananassa Duch.). Transcriptional profiling was performed in different tissues, fruits of different developmental stages, and leaves under different abiotic stresses. Functionality of YUCs was studied in transgenic F. vesca by over-expression or RNA interference, also in F. × ananassa by tobacco rattle virus (TRV)-induced gene silencing (VIGS) technique. The genetic study showed that FvYUC6 has important role in vegetative and reproductive development in woodland strawberry. VIGS experiment provided evidence that the gene FaYUC11, most homologous to AtYUC11, is crucial for receptacle enlargement in octoploid strawberry. Also, our work supports the interpretation that auxin biosynthesis system in strawberry holds flexible responses to developmental and environmental signals. These results will provide useful information for strawberry production to improve plant growth and fruit yield.