A Preliminary Study Of Arabidopsis Anther Development Gene Mps1 And Ams Functions

The spindle is an array of microtubules, microtubule motor proteins, and a series of other complex, which is essential for segregating chromosomes to generated cells during cell division. The spindle in higher plants is lack of centrosomal-like structures as in animals and yeasts, so the mechanism of spindle organization in higher plants should be different form others. Now the mechanism, especially the molecular mechanism of spindle organization in higher plants is still not well understood. We isolated an Arabidopsis T-DNA mutant with severely reduced male and female fertility, and cloned the mutated gene At5g57880. Cytological analysis showed a large number of abnormal tetrads in mutant anther, especially hexads, pentads and irregular tetrads, which indicated abnormalities in meiosis. Further analysis showed that chromosome segregation was abnormal in both male and female mps1 meiocytes. Most chromosomes separated to three or more directions at anaphase, or showed an uneven separation to two directions. Immunolocalization showed unequal bipolar or multipolar spindles in mps1 meiocytes, which indicated that aberrant spindles resulted in disordered chromosome segregation. The MPS1 protein encodes a 377 amino acid functional unknown protein with putative coiled-coil motifs, and a nuclear localization signal in N terminus. RT-PCR showed MPS1 is expressed in almost all tissues, especially in young seedling. In situ hybridization analysis showed that MPS1 is strongly expressed in both male and female meiocytes. The possible role of MPS1 in meiotic spindle organization is also discussed. In Arabidopsis, the tapetum plays important roles in anther development, providing enzymes for callose dissolution and materials for pollen wall formation, and supplying nutrients for pollen development. Tapetum development is a complicated and precise process contains cell differentiation, material secretary, programmed cell death. Here we report the identification and characterization of a T-DNA mutant ams-2, and further elucidate novel functions of AMS in tapetum development. Cytological analysis showed that tapetum vaculation in ams-2 was earlier than the ams mutant had been published. The tapetal cell became hypertrophy and vaculation before tetrad releasing. Transmission Electron Microscopy (TEM) examination further revealed tapetum didn't differentiate into secretary- type cell at stage 6. There is no material required for microspore and pollen development in tapetal cell. TUNEL assay showed that there was no signal of PCD in tapetum, which results in aborted tapetum degradation at later stages. Callose staining and gene expression analysis suggested that AMS may be a crucial component in controlling callose dissolution. In situ hybridization analysis revealed that AMS is highly expressed in tapetum and meiocytes during anther development. AMS encodes a bHLH transcription factor, it showed transactivating ability in yeast experiment, and the activation domain was in N terminal. In conclusion, our results showed that AMS plays a vital role in tapetal differentiation and development.