Abstract
In this work, a new terrestrial cyanobacterial species, Oculatella lusitanica LEGE 161147, was isolated and characterized using a polyphasic approach. Morphologically, O. lusitanica shares characteristics with different Oculatella species (mainly with O. crustae-formantes), lacking distinctive features. However, the phylogeny based on the 16S rRNA gene sequence and the 16S-23S ITS secondary structures support the establishment of this isolate as a new species. O. lusitanica is placed within a clade mainly composed by other Oculatella terrestrial strains; however, it forms a separate lineage. In addition, our species differs from the other Oculatella described so far by lacking the V2 helix within the ITS region. Since cyanobacteria are known to release compounds that promote plant growth and/or increase their tolerance to stresses, the effect of this newly described cyanobacterial species on Lactuca sativa (lettuce) plants development and salinity stress resistance was evaluated. Our results showed that, although the cyanobacterium had no impact on plant growth under the conditions tested, it was able to mitigate the deleterious salinity stress effects on plant size, root and aerial part fresh weight, by eliciting the non-enzymatic antioxidant response system (proline, H2O2 and reduced glutathione). In addition, the microorganism was able to induce a priming effect on lettuce plants by stimulating defensive mechanisms under non-stress conditions, and enhances the activity of nitrogen metabolism-related enzymes glutamate dehydrogenase, glutamine synthetase and nitrate reductase. These results indicate that this native terrestrial cyanobacterial species could be employed as a tool in sustainable agricultural practices.
Highlights
Due to their morphological and metabolic versatility, cyanobacteria are able to colonize and inhabit a variety of habitats ranging from aquatic to terrestrial, including extremeÂngela Brito and Mariana Rocha contributed to the paper.1 i3S—Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal1 3 Vol.:(0123456789)Journal of Applied Phycology natural and anthropogenic substrates such as sandstone, granite, limestone and clay, leading to the formation of complex microbial mats (Hauer 2007; Hauer et al 2015)
Since cyanobacteria are known to release biologically active substances promoting plant growth and/or increase their tolerance to stresses, we evaluated the effects of this native strain on L. sativa plants development and salinity stress resistance
Oculatella is morphologically characterized by the presence of a reddish eyespot in mature apical cells of the trichrome, and the species initially isolated came from hypogean environments
Summary
Journal of Applied Phycology natural and anthropogenic substrates such as sandstone, granite, limestone and clay, leading to the formation of complex microbial mats (Hauer 2007; Hauer et al 2015) They can be considered “ecosystem engineers” due to their ability to modify, maintain and create habitats for other organisms (Jones et al 1994). Among the cyanobacterial genera isolated from terrestrial habitats, one that has been frequently reported is Oculatella Zammit, Billi et Albertano, a member of the family Oculatellaceae (Synechococcales) (Mai et al 2018) This genus was recently separated from Leptolyngbya Anagnostidis & Komárek, a polyphyletic genus in which the species were mainly established using morphological traits (Zammit et al 2012). This photoreceptive structure is most probably associated with the positive phototaxis displayed by Oculatella (Albertano et al 2000; Zammit et al 2012)
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