Fragaria

Fragaria is the taxonomic genus of strawberries, in Rosaceae. Its familiar fleshy structure is an enlarged receptacle bearing many dry achenes. Each achene is a separate fruit enclosing a seed; the common receptacle is therefore anatomically distinct from the individual seed-bearing units. Kew recognizes Fragaria as a genus within Rosaceae.^[ref]

Fragaria vesca, the woodland strawberry, is a diploid experimental representative: its chromosomes occur in two sets. A 2013 study dissected five fruit tissue types at five developmental stages and used RNA sequencing to compare gene expression. Separating seed-associated tissues from the receptacle let the researchers ask which tissue might make a growth signal and which might respond to it.^[ref]

An instructive contrast is to compare a whole-fruit measurement with separate measurements of its achenes and flesh. An increase averaged over the whole structure could reflect a change within one tissue or simply a change in the proportions of tissues sampled. Anatomical dissection makes the biological meaning of a gene expression measurement more precise. Expression patterns suggest mechanisms to test; they do not by themselves prove movement of a hormone from one tissue to another.

Fragaria vesca, the woodland strawberry, is a small perennial flowering plant in Fragaria and Rosaceae. It is a diploid experimental model, with $2n=14$ chromosomes: seven corresponding pairs. Like other strawberries, it bears small dry achenes on an enlarged fleshy receptacle.^[ref]

Its genome illustrates the difference between a cell's chromosome complement and an assembly's reference representation. A draft published online in 2010 and in the 2011 journal volume combined extensive DNA sequencing with a genetic linkage map to anchor sequence into seven reference pseudochromosomes. Seven reference sequences therefore do not mean that ordinary diploid body cells contain only seven chromosomes.^[ref]

The plant also supports experiments connecting anatomy to molecular activity. A 2013 study compared five fruit tissue types across five developmental stages using RNA sequencing. Keeping achenes and receptacle tissues separate allowed gene expression patterns to be assigned to particular parts of the developing structure.^[ref]

For an illuminating comparison, imagine two fruits with the same average expression of a gene but different proportions of seed-bearing and fleshy tissues. Their whole-fruit averages can agree even when corresponding tissue types differ. The relatively tractable genome and dissectible fruit make Fragaria vesca useful for testing such developmental questions.