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Open Access Research article

Genome characteristics reveal the impact of lichenization on lichen-forming fungus Endocarpon pusillum Hedwig (Verrucariales, Ascomycota)

Yan-Yan Wang12, Bin Liu3, Xin-Yu Zhang1, Qi-Ming Zhou1, Tao Zhang12, Hui Li12, Yu-Fei Yu1, Xiao-Ling Zhang1, Xi-Yan Hao3, Meng Wang3, Lei Wang3* and Jiang-Chun Wei1*

Author Affiliations

1 State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China

2 University of Chinese Academy of Sciences, Beijing 100049, China

3 TEDA School of Biological Sciences and Biotechnology, Nankai University, Tianjin 300457, China

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BMC Genomics 2014, 15:34  doi:10.1186/1471-2164-15-34

Published: 17 January 2014

Abstract

Background

Lichen is a classic mutualistic organism and the lichenization is one of the fungal symbioses. The lichen-forming fungus Endocarpon pusillum is living in symbiosis with the green alga Diplosphaera chodatii Bialsuknia as a lichen in the arid regions.

Results

454 and Illumina technologies were used to sequence the genome of E. pusillum. A total of 9,285 genes were annotated in the 37.5 Mb genome of E. pusillum. Analyses of the genes provided direct molecular evidence for certain natural characteristics, such as homothallic reproduction and drought-tolerance. Comparative genomics analysis indicated that the expansion and contraction of some protein families in the E. pusillum genome reflect the specific relationship with its photosynthetic partner (D. chodatii). Co-culture experiments using the lichen-forming fungus E. pusillum and its algal partner allowed the functional identification of genes involved in the nitrogen and carbon transfer between both symbionts, and three lectins without signal peptide domains were found to be essential for the symbiotic recognition in the lichen; interestingly, the ratio of the biomass of both lichen-forming fungus and its photosynthetic partner and their contact time were found to be important for the interaction between these two symbionts.

Conclusions

The present study lays a genomic analysis of the lichen-forming fungus E. pusillum for demonstrating its general biological features and the traits of the interaction between this fungus and its photosynthetic partner D. chodatii, and will provide research basis for investigating the nature of its drought resistance and symbiosis.

Keywords:
Mycobiont; Phycobiont; Lichenization; Symbiosis; Symbiosis-related gene; Photosynthetic products