Isatis tinctoria, aka Isatis indigotica, has long been used as a source of the blue dye, indigo, and numerous phytopharmacological agents. As such, it has received a different kind of attention at the transcriptomic level than other species, broadening our perspective on the study of eXtremophytes.
A. arenosa is a wonderful model for understanding the mechanisms and effects of repeated genome duplication and hybridization events, and for studying ecological adaptation. It is found throughout Europe in a variety of disturbed area types (mountain slopes, forest margins, roadsides, railroad tracks, river banks and grassy and sandy areas), and from sea level up to 2000 m, with genetic specializations to a wide variety of edaphic conditions.
Two species of Xerophyta – X. viscosa and X. humilis – have been studied at the molecular level. Both are native to southern Africa. Like other monocots, Xerophyta spp. lose their chlorophyll during desiccation. Seedlings also lose desiccation tolerance briefly upon germination and recover it gradually during seedling development. X. viscosa, the only species with a sequenced genome, is a chasmophyte. It is also self-incompatible and thus shows a high degree of heterozygosity. In contrast, X. humilis, for which transcriptome resources are available, is a non-chasmophyte.
Schrenkiella parvula – a 7 chromosome member of the Brassicaceae – has an eXtreme ability, in the natural world, to function in the hypersaline conditions surrounding Lake Tuz in central Anatolia, Turkey. It is also notable for its tolerance of high levels of other cations, especially Li+ and Mg2+ and of Boron. These extreme adaptations were central to the initial decision to sequence the genome of this species.