Nexine Layer Controller (NLC)，is Essential For Nexine Deposition And Pollen Wall Gene Relationship In Arabidopsis Thaliana

The pollen wall, as the most complex one in cell wall, has themultifunction for supporting the plant gamogenesis and fertility. Thepollen wall consists of two main layers, the outer exine and inner intine.The exine also contains the sexine and nexine layers. Although pollenwall determination had been investigated extensively, the mechanismof nexine formation remains poorly understood. Here, we reported thata new gene, NEXINE LAYLER CONTROLLER (NLC), is essential for nexineformation of pollen in Arabidopsis thaliana. The nlc mutant exhibitscomplete male sterile phenotype, due to the postmeiotic abortion ofmicrospores. Transmission electron microscopy examination revealedthat the nexine layer and intine structure of nlc microspores are absentduring later anther stages, in despite of normal sexine formation. TheNLC encodes an AT-HOOK family protein that is predominantly locatedin the nucleus. In situ hybridization analysis revealed that NLC isexclusively expressed in tapetal layer at tetrad stage. It demonstratedthat the biosynthesis of nexine was regulated by sporophytictapetum.Further histological staining and expression detectionsuggested that the intine biosynthesis is not affected in nlc, although itsdeposition was aberrant. The genetic pathway(DYT1-TDF1-AMS-AtMYB103-MS1) to the development and function fortapetum was revealed recently. In this pathway the MYB103wasshowed to regulate the sexine formation. with5tapetal transcriptionfactors. Further genetic analysis showed that NLC acts downstream ofAMS and parallel to AtMYB103, which specifically regulates the nexineformation during pollen development. Additionally, the ChIPexperiment showed the AMS could directly regulate the expression ofAtMYB103and NLC. The possible relationship among sexine, nexine andintine in microsporogenesis is also discussed.