Group VII Ethylene response factor diversification and regulation in four species from flood-prone environments

Flooding events negatively affect plant performance and
survival. Flooding gradients thereby determine the dynamics
in vegetation composition and species abundance. In adaptation
to flooding, the group VII Ethylene Response Factor
genes (ERF-VIIs) play pivotal roles in rice and Arabidopsis
through regulation of anaerobic gene expression and antithetical
survival strategies.We investigated if ERF-VIIs have
a similar role in mediating survival strategies in eudicot
species from flood-prone environments. Here, we studied the
evolutionary origin and regulation of ERF-VII transcript
abundance and the physiological responses in species from
two genera of divergent taxonomic lineages (Rumex and
Rorippa). Synteny analysis revealed that angiosperm ERFVIIs
arose from two ancestral loci and that subsequent diversification
and duplication led to the present ERF-VII
variation.We propose that subtle variation in the regulation
of ERF-VII transcript abundance could explain variation in
tolerance among Rorippa species. In Rumex, the main difference
in flood tolerance correlated with the genetic variation
in ERF-VII genes. Large transcriptional differences
were found by comparing the two genera: darkness and dark
submergence-induced Rumex ERF-VIIs, whereas HRE2
expression was increased in submerged Rorippa roots.
We conclude that the involvement of ERF-VIIs in flooding
tolerance developed in a phylogenetic-dependent manner,
with subtle variations within taxonomic clades.