6 Conclusions and perspectives
The appearance and diversification of adaptations to dry environments
and their underlying GRNs have been tightly shaped at cell, tissue and
organismal levels during evolution. These adaptations were crucial for
plants to colonize dry lands and survive variations on water
availability in the environment. Carbon concentration mechanisms,
desiccation tolerance and root impermeabilization are among the main
plant adaptations to dry environments and share a similar pattern of
convergent evolution in phylogenetically distant organisms. However, we
are only starting to understand the evolutionary paths of the GRNs
underpinning these adaptations in individual lineages. More comparative
research between independent evolutions will inform us of the possible
GRN evolutionary paths, including finding out if the same molecular and
regulatory changes have occurred in independent lineages.
Detailed physiological and histological studies combined with advanced
genome and transcriptome sequencing techniques such as TRAP-seq and
single-cell sequencing (Heiman, Kulicke, Fenster, Greengard, & Heintz,
2014; Reynoso et al., 2015; Thellmann, Andersen, & Vermeer, 2020) will
allow us to assess how these adaptations evolved through millions of
years. This information in combination with novel methods to simulate
drought conditions (e.g. Marchin, Ossola, Leishman, and Ellsworth
(2019)) and technologies for plant genetic modification (e.g.
CRISPR/Cas9) will have the power to help on the improvement of plant
performance in dry environments, especially in the current scenario of
increasing climate change. These data will also provide knowledge about
key TFs working upstream of GRNs controlling DT pathways, which are of
potential interest for engineering more drought tolerant crops.