DEX1, A Membrane Localized Protein, Functions In Microspore Development By Modulating ClaS5Expression In Arabidopsis Thaliana

Microsporogenesis in flowering plants plays important roles in sexual reproduction. It has been reported that DEFECTIVE IN EXTNE FORMATIONI (DEXI) is essential for exine pattern formation in Arabidopsis thaliana. However, its role in microspore development has not been fully characterized. Previous study indicated that its pollen wall formation is irregular and primixine formation is delayed. Northern study showed that DEXI was expressed in all the tissure, expecially in the buds. Here, we showed that DEXI was strongly expressed in the tapetum by using RNA in situ hybridization, dexl microspores were degenerated and aborted after release from the tetrads. Callose wall in tetrads was thinner in the dexl mutant than in the wild type, suggesting that DEXI affects callose formation at the tetrad stage during anther development. Further RT-PCR and real-time PCR analyses revealed that ClaS5was greatly down-regulated in dexl plants. DEXI encodes a membrane protein with one transmembrane domain, one intracellular domain and one extracellular domain. Our data provide evidence that DEXI is essential for microspore development possibly through affecting the expression of ClaS5.