MOLECULAR-CLONING AND MESSENGER-RNA LOCALIZATION OF TOMATO POLLEN PROFILIN

The actin cytoskeleton plays an important role in the growth of pollen tube. The actin-binding protein profilin could play a role in regulat ing the organization of the actin filaments. Using the RT-PCR techniqu e, we isolated a cDNA clone (designated LePro1) encoding profilin from pollen grains of tomato (Lycopersicon esculentum Mill. cv. Moneymaker ). Sequence analysis of the insert shows 87% similarity to tobacco ntP ro2, 78% to timothy grass profilin, 77% to Arabidopsis AthPRF4, 77% to maize ZmPro3, and 73% to birch profilin. Both quantitative PCR and RN A gel blot analyses demonstrated that LePro1 is expressed in a tissue- or cell-type specific manner in the tomato plant. In situ hybridizatio n of 2 mu m thick anther sections using a non-radioactive labeling met hod reveals that LePro1 is expressed only in pollen grains, with undet ectable transcription in other parts of the anther or other organs. Ph ylogenetic analysis of amino acid sequences of 18 plant profilins indi cates that two distinct profilin gene classes are present in higher pl ants. One is pollen-specific, another is constitutive. LePro1 belongs to the former class.