Eggplant Genetic and Chemical Diversity, Investigated In The Context Of Domestication

Eggplants (Solanum melongena L.) were domesticated in tropical Asia where they are used abundantly as both food and medicine. Human selection produced hundreds of landraces that differ in morphology and chemistry in relation to local preferences. Here I present a study of the genetic, phytochemical, and ethnobotanical diversity of Asian eggplant landraces and wild relatives, which together aimed to identify the molecular and chemical differences among lineages, correlate these differences with domestication and possible selection pressures, and generate hypotheses about shifts in gene regulation that could have caused these differences.

Population genetic and phylogeographic analyses suggest that eggplants were domesticated multiple times, likely in India, southern China, and the Indo-Malayan islands. Analyses of eggplant chemical profiles spanning 43 phenolic compounds, many of which have therapeutic and flavorful qualities, were compared to genetic and geographic data. Results showed that these putatively independently domesticated lineages have significantly different levels of hydroxycinnamic acid polyamine amides, which actually may contribute to fruit texture and size, in addition to health beneficial qualities of the fruit.

To better understand how changes in gene regulation may have resulted from domestication, chemical differences among lineages were correlated to gene expression levels of 13 enzymes in the phenolic pathway. Results revealed that differential expression of six genes may underlie the different phytochemical profiles; these genes encode spermine and spermidine hydroxycinnamoyl transferases, hydroxycinnamoyl transferase, and cinnamoyl 3-hydrolase. Together, results point to selection on the regulation of these key genes as part of the domestication process in the multiple centers.