Developmental Mechanisms of Fleshy Fruit Diversity in Rosaceae.

Rosaceae (the rose family) is an economically important family that includes species prized for high-value fruits and ornamentals. The family also exhibits diverse fruit types, including drupe (peach), pome (apple), drupetum (raspberry), and achenetum (strawberry). Phylogenetic analysis and ancestral fruit-type reconstruction suggest independent evolutionary paths of multiple fleshy fruit types from dry fruits. A recent whole genome duplication in the Maleae/Pyreae tribe (with apple, pear, hawthorn, and close relatives; referred to as Maleae here) may have contributed to the evolution of pome fruit. MADS-box genes, known to regulate floral organ identity, are emerging as important regulators of fruit development. The differential competence of floral organs to respond to fertilization signals may explain the different abilities of floral organs to form fleshy fruit. Future comparative genomics and functional studies in closely related Rosaceae species with distinct fruit types will test hypotheses and provide insights into mechanisms of fleshy fruit diversity. These efforts will be facilitated by the wealth of genome data and resources in Rosaceae.