| Pollen is the carrier of male germ cells in higher plants.There is a complicated pollen wall structure on the pollen surface to ensure pollen development.The pollen wall of different species presents different morphological characteristics,called pollen wall pattern.Pollen wall formation is a complicated process,and the primexine is regarded as the template of pollen wall pattern.Up to now,several genes related to pollen wall formation have been reported,such as DEX1,NEF1,EFD and NPU.We used the fluorescent protein VENUS to be fused with DEXY and successfully complement the defects in dexy mutant plants.The results showed DEXY was highly expressed in tapetum,microsporocytes and mature pollen grains.The DEXY which is specifically expressed in the tapetum or microsporocytes cannot restore the fertility of the dexy mutant,indicating that both tapetal and microsporocyte DEXY are required for primexine formation.The overexpression of DEXY in tapetum led to the male sterility.Further TEM observation showed that the primexine deposition and undulated plasma membrane formation were both abnormal in the overexpression lines.This indicates that an appropriate amount of DEXY is necessary for primexine formation.In addition,yeast two-hybrid experiment showed that DEXY can interact with EXO70G1,suggesting that DEXY might be involved in exocytosis.Further treatment of the wildtype Arabidopsis with endosidin 2,an inhibitor of EXO family protein,resulted in male sterility,and the pollen wall pattern of the sterile plants was severely destroyed,suggesting that DEXY may interact with exocyst to affect primexine formation.In addition to the sporophyte defects during early pollen development,dexy was also defective in male gametophytegenesis.Almost half of the pollens in dexy/+ mutant were aborted.The reciprocal crossing results showed that the male gamete transmission rate in the heterozygous mutants was significantly decreased,indicating that DEXY also functions in the gametophyte stage. |
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