TPR domain coding gene ST2 may be involved in regulating tillering and fertility in rice

A decrease in the tiller number and male sterility will lead to a decline in the rice yield. Therefore, it is significant to study the molecular mechanism of controlling the tiller number and regulating the male reproductive development. The mutant st2 (single tiller 2) was induced by ethyl methane sulfonate (EMS) in the indica maintainer line Xinong 1B and showed single tillering and male sterility. I2-KI staining showed that the st2 pollen was aborted. The scanning electron microscope (SEM) observation underlined that the anther of st2 became smaller, the wax of the epidermis reduced, the inner wall shrank and the Ubisch body decreased, the pollen collapsed, and the germination pore developed abnormally. The genetic analysis discovered that the trait was controlled by a single recessive nuclear gene located on chromosome 3. LOC_Os03g05540 encoding a tetratricopeptide repeat (TPR) domain was identified as the candidate gene by sequencing. The quantitative real-time polymerase chain reaction (qRT-PCR) analysis indicated that ST2 was highly expressed in the stem apical meristem (SAM) and the initial stage of meiosis during the anther development. The subcellular localisation indicated that ST2 is a nuclear and plasmic localisation protein. The homology analysis demonstrated that ST2 was evolutionarily conserved. These results laid a foundation for further study of the ST2 function.