Novel localization of callose in the spores of Physcomitrella patens and phylogenomics of the callose synthase gene family.
OBJECTIVE
Callose involvement in spore development is a plesiomorphic feature of land plants. Correlated light, fluorescence and immuno-electron microscopy was conducted on the developing spores of Physcomitrella patens to probe for callose. Using a bioinformatic approach, the callose synthase (PpCalS) genes were annotated and PpCalS and AtCalS gene families compared, testing the hypothesis that an exine development orthologue is present in P. patens based on deduced polypeptide similarity with AtCalS5, a known exine development gene.


METHODS
Spores were stained with aniline blue fluorescent dye. Capsules were prepared for immuno-light and immuno-electron microscopy by gold labelling callose epitopes with monoclonal antibody. BLAST searches were conducted using the AtCalS5 sequence as a query against the P. patens genome. Phylogenomic analysis of the CalS gene family was conducted using PAUP (v.4.1b10).


RESULTS
Callose is briefly present in the aperture of developing P. patens spores. The PpCalS gene family consists of 12 copies that fall into three distinct clades with AtCalS genes. PpCalS5 is an orthologue to AtCalS5 with highly conserved domains and 64 % similarity of their deduced polypeptides.


CONCLUSIONS
This is the first study to identify the presence of callose in moss spores. AtCalS5 was previously shown to be involved in pollen exine development, thus making PpCalS5 a suspect gene involved in moss spore exine development.
Schuette
Scott
S
Department of Plant Biology-6509, Southern Illinois University, Carbondale, IL 62901, USA. renzlab@siu.edu
Wood
Andrew J
AJ
Geisler
Matt
M
Geisler-Lee
Jane
J
Ligrone
Roberto
R
Renzaglia
Karen S
KS
D000595:Amino Acid Sequence; D019068:Bryopsida / Q000166:cytology / Q000201:enzymology* / Q000235:genetics / Q000648:ultrastructure; D023281:Genomics; D005936:Glucans / Q000378:metabolism*; D005964:Glucosyltransferases / Q000737:chemistry / Q000235:genetics*; D007150:Immunohistochemistry; D008969:Molecular Sequence Data; D005810:Multigene Family; D010802:Phylogeny; D016415:Sequence Alignment; D013170:Spores / Q000166:cytology / Q000201:enzymology* / Q000235:genetics / Q000648:ultrastructure
D005936:Glucans; C048306:callose; D005964:Glucosyltransferases; C020570:1,3-beta-glucan synthase