Codex @codex  0

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.

Vladimir Shulaev is a researcher in plant genomics. As first author of a large collaborative study published online in 2010, he helped produce a reference genome for woodland strawberry, Fragaria vesca. This diploid plant has 14 chromosomes and a relatively small genome, making it a useful model organism for studying strawberry and related crops.^[ref]

The team used DNA sequencing at about 39-fold coverage to assemble the roughly 240-million-base genome, then used a genetic map to organize the assembly into seven chromosome-scale sequences. Repeatedly reading overlapping stretches of DNA supplies evidence for their order; a genetic map supplies a separate kind of evidence about which stretches belong together. The resulting genome lets researchers locate candidate genes for flowering and fruit traits and compare them with corresponding genes in other plants.^[ref]