Functional Analysis Of Arabidopsis Atg58 Gene In Fertilization

Doublefertilization is a peculiar phenomenon for angiosperm. After matures in the anther,pollen germinates and gets into the blastula. Then two sperms and a nutritional cell releases from pollen tubes. Two sperms merge oosphere and polarnucleus respectively. That's the angiosperm. In this process, pollen germination and enlongation are very important. There are many factors affecting the development of the pollen and the apicalgrowth of the pollen tube, for example, ATPase, Ca²⁺, pH and so on.RSSG58 was obtained from screening rice pollen cells and two-cell subtractive library. The gene is strongly expressed in the sperm cells. Atg58 of Arabidopsis thaliana is the homologous gene of RSSG58. We already showed that Atg58 mainly expressed in the mature pollen.We constructed Atg58::GFP vector to see the expression of this gene in the development, generated some transgenic plant expressing the vector and found that Atg58 localizes in cytoplasm. The expression of Atg58 is elevated significantly when the pollens germinate.The gene also expressed in pollen tube. By using the RNAi mutant, we measured the difference of many parameters between the RNAi and wild-type plants , and investigated the activity of ATPase of pollens, staining of the pollens with DAPI and changes in Ca²⁺ fluorescence of pollens. We found that the declined expression of Atg58 cause the reduction of the activity of ATPase in the process of the pollen mature, delay in the division phase from two nucleus to three nucleus, and reduction of the content of Ca²⁺ in the mature pollens. Moreover, the Ca²⁺ polar contribution during elongation of pollen tubes is also affected in Atg58 RNAi mutant plants. These results suggens that Atg58 affects not only the process of the pollen development, but also the elongation of pollen tube.