Aquaporins in the wild: natural genetic diversity and selective pressure in
the PIP gene family in five Neotropical tree species
Delphine Audigeos1, Anna Buonamici2, Laurent Belkadi1, Paul Rymer3, David Boshier3, Caroline ScottiSaintagne1, Giovanni G. Vendramin2, Ivan Scotti1*
1
INRA UMR 0745 EcoFoG (« Ecologie des forêts de Guyane »), Campus Agronomique, BP709 – 97387
Kourou, French Guiana (France)
2
Istituto di Genetica Vegetale, Sezione di Firenze, Consiglio Nazionale delle Ricerche, Sesto
Fiorentino (Firenze), Italy,
3
Dept. of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK
Summary

Tropical trees undergo severe seasonal drought and flooding stress, and their ability to
respond may be a major factor in the survival of these species in their ecosystems,
particularly in relation to global climate change. Aquaporins are involved in the regulation of
water flow and have been shown to be involved in drought response; they may therefore
play a major adaptive role in these species. We describe here genetic diversity in the PIP subfamily of the widespread gene family of Aquaporins in five Neotropical tree species covering
four botanical families.

PIP Aquaporin subfamily genes were isolated, and their DNA sequence polymorphism was
characterised in natural populations. Sequence data were analysed with statistical tests of
selective neutrality. Demographic scenarios were simulated to compare with the observed
results. Chloroplast SSRs were also used to test demographic transitions.

Most gene fragments are very polymorphic and display signatures of balancing selection or
bottlenecks; chloroplast SSR markers have significant statistics detecting population
expansion. Although not imcompatible with a purely demographic scenario, the combination
of all tests favours a selective interpretation.

Balancing selection appears to be widespread on PIP genes in tropical trees, possibly
maintaining high levels of genetic diversity.