Announcing a new website - eXtremeplants.org

At the 2015 meeting, "Surviving the extremes: Abiotic stress tolerance in extremophile plants", held at the Jacob Blaustein Institutes for Desert Research (BIDR), in Israel, many participants were excited about the possibility of a web site devoted to eXtreme plants, or eXtremophytes. Over the next 1.5 years, Simon Barak and John Cheeseman, with the assistance of Alison Cheeseman at birdhive.com and various other folks who contributed background information, put together such a site. It will be fully live at the end of August, 2017. To be informed when that happens, or to become a participant in whatever way you choose, please start by subscribing to the mailing list: send a message of any sort (no subject or content needed) to x-list-join@extremeplants.org.


► The genus Thellungiella is closely related to Arabidopsis thaliana but its species are endemic to saline, resource-poor habitats, making them good models for the evolution of plant adaptation to extreme environments. A draft genome for Thellungiella parvula was published in 2011 and updated in March, 2012*;. Subsequently, the draft genome for T. salsuginea was also published, and together they (and thellungiella.org) were highlighted in the August 16th edition of Genome Biology (thanks to Simon Dittami and Thierry Tonon). The sequencing of both genomes was done entirely with "next generation" techniques (Roche 454 and Illumina Solexa). T. parvula assembled into 1,496 gap-free contigs, closely approximating the estimated genome size of 140 Mb. The genome of T. salsuginea is about 70% larger. In both cases, the sequences were anchored to seven pseudo-chromosomes. Particularly noteworthy was that the T. parvula sequences identified a number of tandem duplications that, by the nature of the duplicated genes, suggest a possible basis for its extremophile lifestyle. T. salsuginea, in contrast, is characterized by many more transposable element derived repetitive sequences. The sequences themselves and an associated BLAST tool are available directly under the "Resources" menu to the left.

A second version of the T. salsuginea genome, under the name Eutrema salsugineum has also been published. The interim sequences, useable subject to the Ft. Lauderdale Protocol, are available here. The complete reference and abstract are in the Literature section, but it does not yet seem to have appeared in databases such as Web of Science. For more details, readers can contact the authors directly: Karen S. Schumaker or Xiangfeng Wang at the University of Arizona. It will be very interesting to see how the final assemblies of the two drafts differ both in sequences and in placement of the genes within the chromosomes.

Since both of these, the technology for sequencing either genomes or transcriptomes, and particularly small ones, has advanced considerably and the prices have come down. It is now feasible to do repeated sequencing and complex transcriptome/treatment studies. Please do, and eXtremeplants will try to keep up with them.

A note on Thellungiella nomenclature: Even though this is old news at this point, it is being left in because of the continuing confusion in nomenclature for this group of plants. In 2013, Koch and German (2013) noted that while the sequencing of the two Thellungiella genomes has been important, older studies on taxonomic diversity, phylogeny and geographic distribution of the species have been neglected. At the same time, a good deal of confusion has arisen over the names and existence of Thellungiella species as names in the molecular literature have been misapplied. In particular, this relates to T. salsuginea and T. halophila, with both transient confusion and propagating errors regarding (1) if they are the same species (they are not), and (2) which one was actually being used in any given study. For those wishing to sequence something novel, neither the species known as T. halophila nor the one known as T. botschantzevii has been done. The latter has apparently received no attention other than in a few taxonomic studies.

In 2005, Al-Shehbaz and Warwick re-classified the Thellungiellas, putting them in the genus Eutrema (see the Koch and German article for references). In 2010, German and Al-Shehbaz, analyzed the group again, and moved T. parvula (or E. parvulum) back out of Eutrema, putting it in a new genus, Schrenkiella, all by itself. Koch and German (2013) have noted that this is one of 20 Brassicaceae genera "who's precise position and tribal affiliation still remains uncertain".

While the confusion summarized by Koch and German is certainly germane and it behooves anyone working with a species to know which one it is, and, of course, to use the most current accepted name. However, given the history of molecular studies involving these species, for now, the name of the website will remain thellungiella.org, rather than thellungiella_or_eutrema_or_schrenkiella.org. Papers addressing any of these monikers will continue to be included in the bibliography, although at this point, literature on wasabi (E. japonica) is not.