Identification of kaonashi mutants showing abnormal pollen exine structure in Arabidopsis thaliana.
Identification of kaonashi mutants showing abnormal pollen exine structure in Arabidopsis thaliana.
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DOI：
10.1093/pcp/pcn131
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发表时间：
2008-10
影响因子：
4.9
通讯作者：
Ishiguro S
中科院分区：
文献类型：
--
作者：
Suzuki T;Masaoka K;Nishi M;Nakamura K;Ishiguro S
外壁是花粉壁的最外层结构，凭借其化学和物理稳定性保护雄配子免受环境的影响。为了明确花粉外壁形成的相关基因，本研究利用扫描电镜技术对花粉外壁结构异常的拟南芥突变体进行了筛选。我们分离了12个突变体，kaonashi1（kns1）到kns12，并将它们分为四种类型。1型突变体表现出类似于胼胝质合成酶基因突变体的塌陷外壁结构，表明1型基因参与胼胝质壁合成。2型突变体表现出显着薄外壁结构，可能是由于有缺陷的primexine增厚。3型突变体表现出有缺陷的顶盖形成，因此3型基因是原始顶盖形成或孢粉素的生物合成和沉积所必需的。4型突变体显示密集分布的杆状，表明4型基因决定了原斑形成的位置。所有已鉴定的kns突变体均为隐性突变，表明这些KNS基因在孢子体细胞中表达。与以前已知的外显子缺陷突变体不同，大多数kns突变体表现出正常的育性。图位克隆结果表明，4型基因之一的KNS 2编码蔗糖磷酸合成酶。这种酶可能是合成primexine或胼胝质壁所必需的，这两种酶对probacula定位都很重要。对kns突变体的分析将为理解外壁组分的生物合成机制和外壁结构的构建提供新的知识。
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.