YUCCA type auxin biosynthesis genes encoding flavin monooxygenases in melon: Genome-wide identification and developmental expression analysis

• Nine loci for YUC-like FMOs were identified in melon genome.
• Isolation of seven expressed CmYUCs revealed high homology with strawberry FMOs.
• Seven CmYUCs are differentially expressed in nearly all melon young organs.
• CmYUC6 and CmYUC11 are preferentially transcribed in seeds and fruit mesocarp, respectively.
• IPyA pathway to IAA may have a role in melon fruit development.

Auxin, the first plant hormone identified more than 80 years ago, is critical for nearly all aspects of plant life. As its diverse action and signaling in plants, auxin biosynthesis also has manifold facets. Recently, a simple two-step pathway of auxin biosynthesis called the TAA/YUC pathway has been proposed to be the main source of IAA in plants. Melon, a global crop, holds a key position in the Cucurbitaceae family for its high economic value and as a model to study biologically relevant characters. Here, we identified the YUCCA (YUC) family in this model of genetic system for Cucurbitaceae species. The genome of melon contains at least 9 loci for YUC-like FMOs and 7 members of the family have been successfully isolated in this study. Quantitative RT-PCR analysis shows that CmYUCs are differentially expressed in nearly all melon young organs. All seven CmYUCs were found to be expressed in certain stage(s) of melon fruits. Of the family, CmYUC6 and CmYUC11 are quite noticeable due to their high expression in seeds and mesocarp of fruits, respectively. In sum, this work supports that the TAA/YUC pathway to IAA may have a role in melon fruit development.