Multidisciplinary approach to describe Trebouxia diversity within lichenized fungi Buellia zoharyi from the Canary Islands

Abstract

The Canary Islands are famous for their extraordinary biodiversity; however, lichenized algae have only been studied partially. Buellia zoharyi is a circum-Mediterranean/Macaronesian species that usually occurs in semi-arid areas of the Mediterranean, but occasionally some interesting communities of this species grow on basaltic lava flows in Lanzarote, Fuerteventura and Tenerife. Those three locations showed similar ecological conditions, but different mean annual temperatures. Here we applied a multidisciplinary approach to describe microalgae diversity from B. zoharyi covering the entire described range of distribution in the Canary Islands. Photobionts were characterized in symbiosis using molecular and microscopic techniques. Different Trebouxia spp. were detected as primary photobiont in each island (Trebouxia cretacea-Fuerteventura, T. asymmetrica-Lanzarote and Trebouxia sp.`arnoldoi´-Tenerife). Coexistence of various Trebouxia spp. within a thallus were detected by using specific primers-PCR. Those three photobionts were isolated and cultured under laboratory conditions. Different phytohormone profiles were obtained in the isolated strains which suggest different internal signalling needs. In addition, we characterized the response of the isolated strains to different temperatures using chlorophyll fluorescence. T. asymmetrica did not modify their F v /fm values with respect to temperature acclimation. In contrast, Trebouxia sp.`arnoldoi'and T. cretacea were more sensitive to changes in growing temperature decreasing Fv/fm at 17°C. Our results indicate that B. zoharyi is flexible regarding the photobiont choice depending on the region, and suggest that bioclimatic factors could influence the myco/photobiont association patterns.

Watanabea green microalgae (Trebouxiophyceae) inhabiting lichen holobiomes: Watanabea lichenicola sp. nova

“…Microalgae of the genus Trebouxia were detected as the primary symbiotic partner of the B. zoharyi samples examined here, using the universal algal primers on the lichen DNA extraction. As in previous studies (Chiva 2020;Molins et al 2020;Moya et al 2020), the ultrastructure of symbiotic microalgae observed in lichen fragment of both thalli (MT27 and TE1) fits with typical features of the genus Trebouxia (Appendix S4 in the Supporting Information). In studies carried out on the diversity of microalgae in lichen thalli by massive sequencing (454, Illumina), several genera of green microalgae were always detected (Moya et al 2017;Molins et al 2021), although in a low proportion and, in general, their sequences are not usually available in GenBank.…”

“…The Mediterranean biocrust-forming lichen Buellia zoharyi Galun (Chiva et al 2019) hosted the Trebouxia genus as its main symbiont (Molins et al 2020); meanwhile, additional algae could also be associated with the lichen thalli. These additional microalgae have been isolated and investigated in detail in this manuscript using an integrative approach, by internal transcribed spacer region (ITS) phylogeny, small subunit ribosomal region (SSU) phylogeny, and light and confocal microscopy to ascertain their taxonomic position and phylogenetic relationships.…”

Lichen algae: the photosynthetic partners in lichen symbioses

“…Data from molecular markers have also addressed this question. Some authors found no evidence of multiple photobiont genotypes in single thalli examined Beck & Koop 2001;Singh et al 2017;Škaloud et al 2018); others found occasional occurrences (Guzow-Krzemińska 2006;Bačkor et al 2010;Muggia et al 2013;Nyati et al 2013;Řidka et al 2014;Onuţ-Brännström et al 2018;Vančurová et al 2018;Molins et al 2020), or frequent presence (Piercey-Normore 2006; Muggia et al 2014;Park et al 2015;Dal Grande et al 2018;Osyczka et al 2021). Intrathalline populations of Trebouxia can also vary in simple sequence DNA regions, which may result from clonal replication errors (Mansournia et al 2012;Dal Grande et al 2014a).…”

Choosing the Right Life Partner: Ecological Drivers of Lichen Symbiosis

“… Paul et al (2018) mentioned difficulties with Sanger sequencing as a possible indicator of algal plurality (i.e., the co-occurrence of multiple phycobionts in individual lichen thalli). Several authors found phycobionts with different ecological optima in a single thallus ( Casano et al, 2011 ; Gasulla et al, 2020 ; Molins et al, 2020 ), which was also the case of multiple Chloroidium spp. in S. vesuvianum thalli.…”

“…Since lichen phycobionts in this region have remained almost unresearched (past studies involved only a limited number of samples; Muggia et al, 2014 ; Leavitt et al, 2015 ; Moya et al, 2015 , 2018 ; Boluda et al, 2019 ; Molins et al, 2020 ), our aim was to supplement the missing information on photobiont diversity in this study area and explore ecological factors shaping symbiotic relationships. Moreover, several studies have documented the phycobionts that are shared by diverse lichen species/genera ( Bačkor et al, 2010 ; Vargas Castillo and Beck, 2012 ; Peksa et al, in preparation), whereas other studies failed to search for the source of lichen phycobionts ( Vančurová et al, 2020 ).…”