Genome characteristics reveal the impact of lichenization on lichen-forming fungus Endocarpon pusillum Hedwig (Verrucariales, Ascomycota).
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.
Yan-Yan
YY
Wang
Bin
B
Liu
Xin-Yu
XY
Zhang
Qi-Ming
QM
Zhou
Tao
T
Zhang
Hui
H
Li
Yu-Fei
YF
Yu
Xiao-Ling
XL
Zhang
Xi-Yan
XY
Hao
Meng
M
Wang
State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China. wanglei@nankai.edu.cn.
Lei
L
Wang
Jiang-Chun
JC
Wei
D001203:Ascomycota / Q000145:classification / Q000235:genetics*; D000460:Chlorophyta / Q000378:metabolism / Q000382:microbiology; D018920:Coculture Techniques; D055864:Droughts; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D016681:Genome, Fungal; D009005:Monosaccharides / Q000378:metabolism; D005810:Multigene Family; D010802:Phylogeny; D012326:RNA Splicing; D015398:Signal Transduction / Q000235:genetics; D013559:Symbiosis / Q000235:genetics*; D014158:Transcription, Genetic
D005656:Fungal Proteins; D009005:Monosaccharides