Life at the extreme: lessons from the genome

Abstract

Extremophile plants thrive in places where most plant species cannot survive. Recent developments in high-throughput technologies and comparative genomics are shedding light on the evolutionary mechanisms leading to their adaptation.

Figure 1

Some examples of extremophiles providing genome- or transcriptome-level data relevant to abiotic stress adaptation. These species are representative of those listed in Table 1. (a) The shores of Lake Tuz in central Anatolia (Turkey) were the original collection site for Thellungiella parvula (b). Note the extensive salt flat where an ephemeral lake would be in a rainy season. (c) Mesembryanthemum crystallinum, known as the common ice plant for the salt crystals excreted from bladder cells on the leaves and stems. (d) Salicornia europaea (a relative of S. brachiata, Table 1) shown in the mud flats at Bull Island, Dublin, Ireland. (e) Heritiera litoralis, one of 27 species in North Queensland, Australia, shown growing along a creek with salinity varying between fresh water and ocean water. (f) Rhizophora mangle, shown as an ocean-fringing forest in the background and as substrate-stabilizing pioneers in the foreground.

Figure 2

Gain of stress-related gene copies through duplication in Thellungiella parvula. Genomic regions containing homologs of NHX8, encoding a plasma membrane Li⁺ transporter [42], and AVP1, encoding a vacuolar proton transporter [79], were compared between T. parvula (Tp) and Arabidopsis thaliana (At). Shown are five colinear genes adjacent to NHX8 and AVP1 in the two species. Red arrows indicate duplications. (a) NHX8 is duplicated in tandem into three copies in T. parvula. (b) AVP1 homologs are duplicated and translocated from T. parvula chromosome 5 to chromosome 1. The colinear genomic region in A. thaliana chromosome 1 contains rolling-circle (RC)/helitron transposable elements in the place of an AVP1 homolog (dashed lines), suggesting a possible involvement of transposable elements in the translocation in an ancestor of the two species. The naming of T. parvula genes is according to version 2 of the genome [80].