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How one badass grass thrives at the thermal limits of eukaryotic life
Sejarah Poaceae
It ' s not an exaggeration to say grasses as a family have adapted amazingly well to most habitats on earth . But there is at least one species that takes that adaptability to new levels .
Living in the active geothermal areas of Yellowstone National Park takes some major adaptations . It is an extreme and hostile environment with rhizosphere temperatures exceeding 40 ° C . Many proteins denature above 41 ° C and in people a body temperature at 43 ° C or above normally results in death or at the least serious brain damage and cardiorespiratory collapse .
Current Address : “ Life among the grasses ” Reprinted From : http :// bit . ly / 2PFtDdy
In such an extreme environment , there are only nine vascular plants that have managed to successfully colonize this habitat . Chief among them are the grasses , which are both the most prevalent and most heat-resistant species in the area . But the award for the most extreme plant goes to Dichanthelium thermale ( formerly a subspecies of D . lanuginosum ), which was flourishing in soils with an average of 44 ° C and a recorded maximum of 57 ° C ! ( Stout and Al-Niemi , 2002 )
When researchers studied D . thermale , they found that it was even more amazing than they initially thought . This grass species had little problem living at the absolutely mind-boggling temperature of 65 ° C for days on end , and they discovered that this ability was the result of symbiosis with a new endophytic species of the fungal genus Curvularia ( Redman et al , 2002 ).
Curvularia protuberata was found in the roots , leaves , crowns , and seed coats of D . thermale , and neither the grass nor the endophyte could survive on its own above 38 ° C . But when endophyte-free grass was inoculated with the fungus , it regained its remarkable thermotolerance .
Figure 1 : Dichanthelium thermale ( formerly a subspecies of D . lanuginosum ) ( James St . John , Wikipedia ).
The researchers surmised that this protection from heat could be the result of several possible mechanisms . One possibility is that the fungal endophyte produces cell wall melanin that may dissipate heat along the hyphae and / or complex with oxygen radicals generated during heat stress . Another possibility is that the endophyte may act as a “ biological trigger ” that allows the symbiotic D . thermale to activate stress response systems more rapidly and strongly than non-symbiotic plants . The symbiosis became even more complex when researchers announced that they had found a third party in the relationship several years later . It turns out that the fungal endophyte was infected with a double-stranded RNA virus , and that its ability to confer thermotolerance on D . thermale was dependent on this infection !
Endophyte-free D . thermale that was inoculated with the fungus + virus survived in heated environments , whereas endophytefree D . thermale inoculated with the fungus without the virus did not survive in the same environment ( Márquez et al , 2007 ).
The unravelling of this complex symbiotic relationship could even have applications in agriculture . When tomato plants were inoculated with the wild-type fungus C . protuberata , their tolerance to heat was improved , albeit only slightly , indicating that the mechanism behind this thermotolerance may be conserved among many different plants .
But this potential novel application in the future would not have been thinkable if it were not for the humble D . thermale in Yellowstone and other geothermal parks . So as we marvel with awe at such an intricate and beautiful example of symbiosis , be sure to also give a respectful nod at this one badass thermotolerant grass and its fungal and viral partners !
Grassroots Vol 21 No 1 March 2021 30