Effect of aposymbiotic conditions on colony growth and secondary metabolite production in the lichen-forming fungus Ramalina dilacerata

Chemosyndrome Variation in Mycobiont Culture and Thallus of <em>Parmelina carporrhizans</em> and <em>Parmelina quercina</em>

“…Further, the chemosyndrome within species and between the aposymbiotic culture and thallus were different, being different and more numerous the secondary metabolites of mycobiont culture than those produced in natural thalli (Table 1, Fig 2). Similar results of variation of chemosyndrome between thallus and culture were reported [19,25,38] arguing that the switch of biosynthetic pathway changed the chemosyndrome [38] by expression of different polyketide synthases [19]. The chemosyndrome variation between thallus and mycobiont culture can be attributed to the absence of carbon sources provided by the photobiont or suboptimal environmental conditions producing stress.…”

“…In resynthesis studies, the decreasing amount of substances in culture after photobiont contact was registered [25]. Moreover, the importance of environmental conditions in chemosyndrome variation in culture was revealed by carbon source in culture media and simulated environmental stress [39] changing the expression of the polyketide synthase genes and chemosyndrome [19]. However, the natural thallus and mycobiont culture can produce the same chemosyndrome [40] at least under certain culture conditions such as at variable temperatures [23,24,39].…”

“…Frequently the environmental conditions as carbon source, PH levels, temperature variation and stress in general modifies the chemosyndrome in mycobiont culture [19,23,24] however P. carporrhizans produced confluentic acid as major compound and practically the same chemosyndrome in both media assayed. How much is the relative weight of genetics and environment in determining the chemosyndrome substances of aposymbiotic mycobiont in laboratory culture and natural pre-thallus stage?…”

“…While lichen substances have interest by the properties exhibited, these substances have had importance in lichen determination by identifying lichen substances as a character in chemotaxonomy. In the second half of the 20th century thin layer chromatography (TLC) has been widely used to identify lichen substances, in the last decades the number of identified lichen substances increased by using more powerful methods [5] as high performance liquid chromatography (HPLC), which have higher sensibility to detect phenolic secondary metabolites [19].…”

“…Indeed, the phenolic pattern can vary substantially between the mycobiont growing in aposymbiotic conditions and the mycobiont associated with its photosynthetic partner (lichen symbionts). These variations have been explained as differences in abiotic factors (nutrients, temperature, pH) [19,23,24] and the modulating effect of the photobiont [25].…”