2,6-Dichlorobenzonitrile, a cellulose biosynthesis inhibitor, affects morphology and structural integrity of petunia and lily pollen tubes

There has been an ongoing debate about the presence and function of cellulose in pollen tube walls. In this study, the role of cellulose in pollen tube growth was analyzed by growing pollen tubes in vitro in the presence of 2,6-dichlorobenzonitrile (DCB), a specific inhibitor of cellulose biosynthesis. Pollen tubes of Lilium auratum and Petunia hybrida were cultured in vitro in the presence of 0.25 to 10 μmol/L DCB. Although pollen germination and growth rate were not affected, petunia and lily pollen tubes frequently ruptured or assumed a distorted, bulbous shape in the presence of DCB. When DCB was added to normally growing petunia pollen tubes, pollen tube rupture was observed within 15 min. Immunolocalization studies showed that in lily pollen tubes treated with DCB, callose deposition occurred. Ultrastructural examination of DCB treated lily pollen tubes revealed a highly disorganized pollen tube wall. Our results suggest that the reduction or lack of cellulose in the presence of DCB causes significant distortion and weakening of the pollen tube cell wall.