Message - 7th IAL Symposium

The 7 th International Association for Lichenology Symposium 2012
1B: Genomic approaches to studying the lichen symbiosis
(1B-P1) Submission ID: IAL0100-00001
GENE EXPRESSION IN DRY AND WET THALLI OF USNEA BISMOLLIUSCULA
Kono M. 1 , Ohmura Y. 2 , Satta Y. 1
1 Department of Evolutionary Studies of Biosystems, The Graduate University for Advanced Studies [Sokendai],
Hayama, Kanagawa, Japan
2 Department of Botany, National Museum of Nature and Science, Tsukuba, Japan
Symbiosis is drawing increasing attention due to its importance in the ecosystem and evolution.
Among a number of symbioses in nature, the lichen is considered as one of the most successful organisms for
having expanded distribution to extreme environments. The ecological success of the lichen is attributed partly
to its ability to switch metabolism on and off according to the water content of thalli. In this study, we focused on
metabolic differences between dry and wet thalli of Usnea bismolliuscula from the view point of gene expression.
For the dry state, thalli kept in a natural dry condition were used, and thalli rehydrated by distilled water were
used for the wet state. The thalli in the both states were exposed to white fluorescent lamp (4.3 μmol m -2 s -1 )
for 1 hour. Total RNAs were extracted from the thalli of each state and differentially expressed genes between
the two states were isolated by subtractive hybridization. BLASTX searches of the sequences obtained from
the experiment were carried out. Possible homologs to fungal genes were detected at amino acid levels such
as 6-phosphofructokinase (60% identity to Mycosphaerella graminicola) and heat shock protein (96% identity
to Alternaria alternata). The results implied a shift in carbon metabolic pathway of the fungus corresponding to
the water content of thalli and an induction of stress response against the low water content. The quantitative
analysis of the results will be performed by RT-PCR. Alternating wetting and drying cycles are considered to be
prerequisites for functioning symbioses of lichens. Therefore, examining gene expression in dry and wet thalli
will shed light on the molecular basis of lichen symbioses.
(1B-P2) Submission ID: IAL0239-00001
ANALYSIS OF FUNCTIONAL GENOMICS OF LICHEN MYCOBIONT ENDOCARPON PUSILLUM
Wang Y. 1 , Zhou Q. 1 , Cao S. 1 , Wei X. 1 , Wei J. 1
1 Key Lab of Systematic Mycology and Lichenology, Institute of Microbiology, Chinese Academy of Sciences, Beijing,
People’s Republic of China
The first full-length cDNA library for lichenized fungi was constructed from cultured mycobiont of the
arid desert lichen Endocarpon pusillum Hedwig. Based on small-scale sequencing results, 111 genes of the
lichenized fungi were identified for the first time. Real-time PCR showed that the size of the mycobiont genome
is 39.13 Mb and the copy number of ribosomal RNA gene repeat units is 43. Genome sequencing showed
that the genome is about 38.4 Mb, almost identical to the size detected by RT-PCR. 12,100 genes have been
detected by large-scale identification of functional genes on before- and after-drought stress transcriptome’s
differential expression of E. pusillum, among which 5,880 genes have obvious change in sequencing signal,
accounting for 48.6% of the total number of genes. Comparing to the before-drought stress transcriptome, there
are 2,225 genes with up-regulation signal and 3,655 genes with down-regulation signal in after-drought stress
transcriptome, accounting for 18.4% and 30.2% of the total number of genes, respectively. Up to now, 1,880
of the variational 5,880 genes have been identified as function-known genes, and 4,000 are function-unknown
genes. In the following work, desiccation tolerance-related genes will be expressed in Escherichia coli system,
and the corresponding functional proteins will be further analyzed.
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