Journal Article

Identification of <i>kaonashi</i> Mutants Showing Abnormal Pollen Exine Structure in <i>Arabidopsis thaliana</i>

Toshiya Suzuki, Kanari Masaoka, Masatomo Nishi, Kenzo Nakamura and Sumie Ishiguro

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 49, issue 10, pages 1465-1477
Published in print October 2008 | ISSN: 0032-0781
Published online October 2008 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcn131
Identification of kaonashi Mutants Showing Abnormal Pollen Exine Structure in Arabidopsis thaliana

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Exine, the outermost architecture of pollen walls, protects male gametes from the environment by virtue of its chemical and physical stability. Although much effort has been devoted to revealing the mechanism of exine construction, still little is known about it. To identify the genes involved in exine formation, we screened for Arabidopsis mutants with pollen grains exhibiting abnormal exine structure using scanning electron microscopy. We isolated 12 mutants, kaonashi1 (kns1) to kns12, and classified them into four types. The type 1 mutants showed a collapsed exine structure resembling a mutant of the callose synthase gene, suggesting that the type 1 genes are involved in callose wall synthesis. The type 2 mutant showed remarkably thin exine structure, presumably due to defective primexine thickening. The type 3 mutants showed defective tectum formation, and thus type 3 genes are required for primordial tectum formation or biosynthesis and deposition of sporopollenin. The type 4 mutants showed densely distributed baculae, suggesting type 4 genes determine the position of probacula formation. All identified kns mutants were recessive, suggesting that these KNS genes are expressed in sporophytic cells. Unlike previously known exine-defective mutants, most of the kns mutants showed normal fertility. Map-based cloning revealed that KNS2, one of the type 4 genes, encodes sucrose phosphate synthase. This enzyme might be required for synthesis of primexine or callose wall, which are both important for probacula positioning. Analysis of kns mutants will provide new knowledge to help understand the mechanism of biosynthesis of exine components and the construction of exine architecture.

Keywords: Arabidopsis thaliana; Exine; kaonashi; Pollen grain; Sucrose phosphate synthase

Journal Article.  7182 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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