Abstract
Carbonic anhydrase (CA) plays an important role in the formation and evolution of life. However, to our knowledge, there has been no report on CA isoenzyme function differentiation in fungi. Two different CA gene sequences in Aspergillus nidulans with clear genetic background provide us a favorable basis for studying function differentiation of CA isoenzymes. Heterologously expressed CA1 was used to test its weathering ability on silicate minerals and real-time quantitative PCR was used to detect expression of the CA1 and CA2 genes at different CO2 concentrations and in the presence of different potassium sources. The northern blot method was applied to confirm the result of CA1 gene expression. Heterologously expressed CA1 significantly promoted dissolution of biotite and wollastonite, and CA1 gene expression increased significantly in response to soluble K-deficiency. The northern blot test further showed that CA1 participated in K-feldspar weathering. In addition, the results showed that CA2 was primary involved in adapting to CO2 concentration change. Taken together, A. nidulans can choose different CA to meet their survival needs, which imply that some environmental microbes have evolved different CAs to adapt to changes in CO2 concentration and acquire mineral nutrition so that they can better adapt to environmental changes. Inversely, their adaption may impact mineral weathering and/or CO2 concentration, and even global change.
Highlights
Carbonic anhydrase (CA) catalyzes the reversible hydration of carbon dioxide: CO 2 + H 2 O ↔ H+ HCO− 3(Meldrum and Roughton 1933; Tripp et al 2001)
The increased expression of CA by Bacillus mucilaginosus favors its survival when the growth environment lacks Ca2+, but is rich in calcite (Xiao et al 2014). These results suggested that microbial CAs are related to mineral nutrition acquisition
For the effect of CA1 protein on K-feldspar weathering, the results showed that the average K+ concentration was almost equal to that of the group without added proteins (Table 1)
Summary
Animal CA exists in different tissues and plays an important part in a variety of physiological processes such as: bone formation, calcification, ion transportation, acid-base balance maintenance, and acid-base transportation (Gilmour and Perry 2009). It is important for the photosynthesis of many green plants (Badger and Price 1994; Badger 2003) and algae (Badger et al 2002; Moroney et al 2004) because of its catalytic action which provides sufficient bicarbonate (Wang et al 2011).
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