Influence of temperature on the expression of the rice sucrose transporter 4 gene, OsSUT4, in germinating embryos and maturing pollen

Rice (Oryza sativa L.) sucrose transporter 4 (OsSUT4) is a rice sucrose transporter family gene. During the early seed germination stage, OsSUT4 was substantially expressed in seed aleurone layer, scutellum, and embryonic vascular bundle. The OsSUT4 mRNA level in the embryos of seeds that were germinated at 30 °C was higher than that of seeds germinated at 20 °C. The temperature effect on the changes of OsSUT4 promoter activities was consistent with that on OsSUT4 mRNA levels. The OsSUT4 gene expression that occurs in response to temperature might be mediated by soluble sugars as signals that are transported from endosperms. The tissue-specific expression patterns of OsSUT4 found in spikelets were dependent on the developmental stages of rice panicles. The OsSUT4 transcript level in anthers during the post-heading stage was higher than that during the pre-heading stage, and the developmental expression pattern of the OsSUT4 gene in anthers was highly correlated with that of genes encoded sucrose metabolism and starch synthesis enzymes. The OsSUT4 promoter activity was also detected in mature and germinating pollen. Furthermore, the OsSUT4 expression in anthers was down-regulated at low temperature (i.e., 15/13 °C) compared with that at 30/25 and 35/30 °C. In conclusion, the levels of OsSUT4 expressions in germinating embryos and maturing pollen were regulated by temperature, and the expressions of OsSUT4 in embryos and pollen at higher temperature (i.e., 30 and 35 °C) were stronger than that at lower temperature condition (i.e., 15 and 20 °C).