Differential localization of the LIM domain protein PLIM-1 in microspores and mature pollen grains from sunflower

PLIM-1 is a LIM domain protein specifically expressed in pollen grains. Using two PLIM-1-specific monoclonal antibodies we studied its expression and intracellular location at various developmental stages of sunflower (Helianthus annuus L.) pollen. Our studies show that the protein appears at the microspore stage in a limited number of cytoplasmic bodies, becomes undetectable in bicellular pollen, and reappears in tricellular pollen grains in cortical patches particularly concentrated in the F-actin-enriched germination cones of the vegetative cell. The developmental stage-dependent, different location of the protein suggests a dual function during pollen development. While this function in microspore development remains obscure, the high concentration of PLIM-1 in the germination cones of mature pollen suggests that it participates in the germination process as well as in pollen tube growth.