OsAPT1 a Pollen Preferentially Expressed Gene Is Essential for Pollen Tube Germination and Elongation in Rice

Pollen tube germination and elongation are important processes for double fertilization in flowering plants. However, little is known about the regulatory mechanism of pollen germination and tube growth in rice. Here, we reported that OsAPT1, a pollen-high expression gene and encoding a putative APT1 protein in Oryza sativa, regulating pollen tube germination and elongation in rice. Real-time quantitative PCR (qRT-PCR) and in situ hybridization analysis showed high expression level of OsAPT1 at late stage of microsporogenesis including late uninucleate stage, binucleate pollen stage, and mature pollen grains. OsAPT1 RNA interference (OsAPT1-RNAi) lines showed that the pollen tube germination and elongation rate were decreased. Compared with wild type (WT), the integrity and assembly of actin microfilaments were abnormal in hydrated pollen grains of OsAPT1-RNAi plants, and the fluorescence signals of actin microfilaments were altered in the pollen tube of OsAPT1-RNAi plants. GO analysis of the co-expressing genes of OsAPT1 showed that the GO terms such as pollination, cell growth, cellular cytoskeleton organization, and motor activity were enriched. In addition, the qRT-PCR results showed variations in the expression of some genes related to pollen tube growth. Overall, our results indicated that OsAPT1 is required for pollen tube germination and elongation in rice.