ST273是拟南芥绒毡层和小孢子发育的必需基因

ST273 Is Essential for Tapetum and Microspore Development in Arabidopsis thaliana

绒毡层在拟南芥花药花粉发育过程中具有重要作用,包括分泌降解胼胝质的胼胝质酶、为花粉壁的形成提供原料以及为小孢子发育提供营养物质。本文通过对拟南芥雄性不育突变体st273的分析,研究了ST273基因在花药花粉发育过程中的功能。st273是通过T-DNA插入诱变野生型拟南芥得到的一株突变体,遗传分析表明st273是单隐性核基因控制的。利用图位克隆的方法对不育基因ST273进行了定位,结果表明ST273基因与拟南芥第三条染色体上分子标记CIW11连锁。生物信息学分析发现该分子标记附近有一个调控花粉发育的基因TDF1。测序分析结果表明在st273突变体中,TDF1基因第三个外显子上459位的碱基发生了由G459变成了A459的单碱基变化,导致ST273基因该位点提前终止突变。等位分析结果表明st273与tdf1是等位突变体。st273突变体营养生长期发育正常,但生殖生长发育出现异常。亚历山大染色结果显示st273突变体花药中没有花粉。组织切片观察结果表明,突变体花药绒毡层异常肥大且空泡化,四分体不能正常释放小孢子,最终无法形成花粉。这些结果揭示了ST273蛋白质参与调控了绒毡层和小孢子发育过程。

In Arabidopsis, the tapetum plays important roles in anther and pollen development by providing enzymes for callose dissolution, materials for pollen-wall formation, and nutrients for microspore development. This paper describes the functional analyses of the ST273 gene in anther and pollen development by using Arabidopsis male sterile mutant st273. Mutant st273 was identified from a T-DNA insertion mutant population, and genetic analysis showed that st273 mutant was controlled by a single recessive nuclear gene. A map-based cloning approach was used, and ST273 gene was mapped to be linked to a molecular marker CIW11 on chromosome 3. Bioinformatics analysis revealed that there is a TDF1 gene near the marker CIW11. Sequencing analysis indicated that st273 mutant had a G459 to A459 base- pair change in the third exon of TDF1 gene, which resulted in premature termination mutation in this region. Allelism test indicated that ST273 and TDF1 belong to the same locus. The mutant plant grows normally during the vegetative growth stage, but show developmental defects at the reproductive growth stage. Alexander staining showed that there was no pollen in the mature anther locule. Cytology observation indicated that the mutant tapetum was enlarged and vacuolated, the tetrads could not release the microspores timely, and finally no pollen was formed in the anther. These results demonstrated that ST273 protein plays an important role in tapetum and microspore development.