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Plant “Extremophiles”?

Recently, I was reading about a new species of metal-eating plant discovered in the Philippines, and I discovered a new word (to me, at least).

This new word is “extremophyte“.

Simply put, most extremophytes are plants evolutionarily adapted to thrive in highly stressful environments. Physically stressful, that is, such as extremely high or low pH soils, very high or very low temperatures, highly saline soils, or geochemically toxic soils (think heavy metal… no, not Metallica…. heavy metals such as lead or mercury). I think these plants are more commonly referred to as “plant extremophiles”.

Extremophiles = living organisms that “love” extreme environments.

Perhaps a more precise definition of “extremophiles” would be: organisms, primarily microorganisms, that have evolutionarily adapted to extreme physical conditions, such as extremely acidic or alkaline pH, boiling hot temperatures, subfreezing cold, high concentrations of toxic compounds (think arsenic), etc.

In other words, these organisms survive, even thrive, under physical conditions that would be lethal to most other living organisms on Earth.

Anyway, back to the extremophytes….

A New Name For Weird Plants?

A search for the term “extremophyte” on Google Scholar revealed that it hasn’t been used in the scientific literature very much, and most instances of the word occurred after 2004.

Google the word “extremophyte”, and some pretty interesting results pop up, especially Dr. Neal Stewart’s Weird Plant Genomics webite.

Dr. Stewart is interested in two kinds of unusual plants, primarily from a genetic standpoint. According to his website, he is interested in (1): “plants that produce novel proteins and metabolites (but not drugs, which is another part of the project). The discovered genes can subsequently be used in genetic engineering and synthetic biology.” and (2) “plants with novel properties and behaviors. The genes novel to fascinating plants that do uncommon things will be excellent teachers…

To see a partial list of Dr. Stewart’s unique plants, please click here (PDF).

One of the most interesting plants on his list is Dictamnus alba, the so-called “gas plant” (see the YouTube video below)

As exemplified by Dictamnus alba, some of Dr. Stewart’s “extremophytes” are not necessarily adapted to extreme environments, but are simply “plants that do uncommon things”. However, most research interest seems to be on the extremophytes adapted to stressful environments.

Weird Plants = Weird Genes?

The chief rationale for genetically sequencing “extremophytes” is to discover novel genes that may help genetically engineer crop plants to be more stress-tolerant.

…extremophytes [may] have more activated forms of genes or gene products that function in tolerance;…” and “We will not be able to determine the genetic bases of those specialized mechanisms without effective extremophyte genetic models.” (from Ref. 1 below; see also Ref. 2)

References

1. Inan, G., et al. (2004) “Salt Cress. A Halophyte and Cryophyte Arabidopsis Relative Model System and Its Applicability to Molecular Genetic Analyses of Growth and Development of Extremophiles.” Plant Physiology, Vol. 135, pp. 1718-1737. (Full Text)

2. Amtmann, A., H. J. Bohnert, and R. A. Bressan (2005) “Abiotic Stress and Plant Genome Evolution. Search for New Models.” Plant Physiology, Vol. vol. 138, pp. 127-130. (PDF)

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