Arabidopsis Thaliana Auxin Response Factor ARF17 Regulates The Growth Of Pollen Tubes

Since the fertilization of higher flowering plants is completed by the pollen tube, it is quite important of studying the growth of pollen tube to understand the mechanism of plant fertilization. Auxin can stimulate pollen tube growth, and here we found ARF17 which is a member of auxin response factor(ARF) family could regulate pollen tube growth. Because plant of arf17 is a completely sterile mutant we isolated arf17 pollen from plant of arf17/+. In vitro germination of arf17 pollen found the gemination rate of arf17 pollen was reduced and the pollen tube growth of arf17 pollen tube was slower than that of the wild type. The callose wall and plug of arf17 pollen tubes was similar to that of wild type pollen tubes however compared with wild type pollen tubes the pectins of arf17 pollen tube was abnormal. Genes of PME which participate in pectin wall modification were down regulated in arf17 pollen and pollen tube. Electrophoretic mobility shift(EMSA) assay and chromatin immunoprecipitation(ChIP) assay showed that the ARF17 protein was able to bind At2g47550 promoter. Tobacco assay indicated that ARF17 could regulate its expression. All of results showed that ARF17 could directly regulate expression of PME and affect pollen tube growth.