A Gain-of-Function Mutation of Arabidopsis Lipid Transfer Protein 5 Disturbs Pollen Tube Tip Growth and Fertilization

作者：Chae Keun; Kieslich Chris A; Morikis Dimitrios; Kim Seung Chul; Lord Elizabeth M^*

来源：Plant Cell, 2009, 21(12): 3902-3914.

DOI：10.1105/tpc.109.070854

During compatible pollination of the angiosperms, pollen tubes grow in the pistil transmitting tract (TT) and are guided to the ovule for fertilization. Lily (Lilium longiflorum) stigma/style Cys-rich adhesin (SCA), a plant lipid transfer protein (LTP), is a small, secreted peptide involved in pollen tube adhesion-mediated guidance. Here, we used a reverse genetic approach to study biological roles of Arabidopsis thaliana LTP5, a SCA-like LTP. The T-DNA insertional gain-of-function mutant plant for LTP5 (ltp5-1) exhibited ballooned pollen tubes, delayed pollen tube growth, and decreased numbers of fertilized eggs. Our reciprocal cross-pollination study revealed that ltp5-1 results in both male and female partial sterility. RT-PCR and beta-glucuronidase analyses showed that LTP5 is present in pollen and the pistil TT in low levels. Pollen-targeted overexpression of either ltp5-1 or wild-type LTP5 resulted in defects in polar tip growth of pollen tubes and thereby decreased seed set, suggesting that mutant ltp5-1 acts as a dominant-active form of wild-type LTP5 in pollen tube growth. The ltp5-1 protein has additional hydrophobic C-terminal sequences, compared with LTP5. In our structural homology/molecular dynamics modeling, Tyr-91 in ltp5-1, replacing Val-91 in LTP5, was predicted to interact with Arg-45 and Tyr-81, which are known to interact with a lipid ligand in maize (Zea mays) LTP. Thus, Arabidopsis LTP5 plays a significant role in reproduction.

• 出版日期2009-12