Callose (beta-1,3 glucan) is essential for Arabidopsis pollen wall patterning, but not tube growth.
BACKGROUND
Callose (beta-1,3 glucan) separates developing pollen grains, preventing their underlying walls (exine) from fusing. The pollen tubes that transport sperm to female gametes also contain callose, both in their walls as well as in the plugs that segment growing tubes. Mutations in CalS5, one of several Arabidopsis beta-1,3 glucan synthases, were previously shown to disrupt callose formation around developing microspores, causing aberrations in exine patterning, degeneration of developing microspores, and pollen sterility.


RESULTS
Here, we describe three additional cals5 alleles that similarly alter exine patterns, but instead produce fertile pollen. Moreover, one of these alleles (cals5-3) resulted in the formation of pollen tubes that lacked callose walls and plugs. In self-pollinated plants, these tubes led to successful fertilization, but they were at a slight disadvantage when competing with wild type.


CONCLUSIONS
Contrary to a previous report, these results demonstrate that a structured exine layer is not required for pollen development, viability or fertility. In addition, despite the presence of callose-enriched walls and callose plugs in pollen tubes, the results presented here indicate that callose is not required for pollen tube functions.
Nishikawa
Shuh-ichi
S
Howard Hughes Medical Institute, Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA. shuh@biochem.chem.nagoya-u.ac.jp
Zinkl
Gregory M
GM
Swanson
Robert J
RJ
Maruyama
Daisuke
D
Preuss
Daphne
D
D000483:Alleles; D017360:Arabidopsis / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D002874:Chromosome Mapping; D017343:Genes, Plant / Q000502:physiology; D005936:Glucans / Q000032:analysis / Q000502:physiology*; D005964:Glucosyltransferases / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D010641:Phenotype; D011058:Pollen / Q000254:growth & development / Q000502:physiology / Q000648:ultrastructure; D018749:RNA, Plant / Q000378:metabolism; D012098:Reproduction
D029681:Arabidopsis Proteins; D005936:Glucans; D018749:RNA, Plant; C048306:callose; D005964:Glucosyltransferases; C020570:1,3-beta-glucan synthase