Microtubule-associated proteins WDL5 and WDL6 play a critical role in pollen tube growth in .

Morphological response of cells to environment involves concerted rearrangements of microtubules and actin microfilaments. A mutant of (), which encodes an ethylene-regulated microtubule-associated protein belonging to the WVD2/WDL family in , shows attenuation in the temporal root growth reduction in response to mechanical stress. We found that a T-DNA knockout of , the closest homolog of , oppositely shows an enhancement of the response. To know the functional relationship between and , we attempted to generate the double mutant by crosses but failed in isolation. Close examination of gametophytes in plants that are homozygous for one and heterozygous for the other revealed that these plants produce pollen grains with a reduced rate of germination and tube growth. Reciprocal cross experiments of these plants with the wild type confirmed that the double mutation is not inherited paternally. These results suggest a critical and cooperative function of WDL5 and WDL6 in pollen tube growth.